Predictors of limited knowledge in insulin injection techniques among non-specialty nurses in Japan

Abstract

Objectives:

Appropriate insulin injection techniques are crucial for ensuring therapeutic efficacy and patient safety; however, most routine injections are administered by nonspecialist nursing staff across various clinical settings. Assessing their current knowledge is essential to identify educational needs and prevent injection-related complications. Therefore, this study aimed to examine the knowledge gaps regarding insulin injection techniques among nondiabetes specialty nurses and identify the factors influencing their knowledge.

Methods:

This cross-sectional questionnaire-based study was conducted on a sample of 815 hospital nurses across Japan using stratified sampling between September and December 2022. The questionnaire included a knowledge quiz, and participants whose scores fell within the lower range were classified into the low-scoring group. Multivariable logistic regression analysis was used to determine the factors associated with the group.

Results:

The lowest correct response rate in the low-scoring group was for the question regarding the name of subcutaneous nodules at the injection site (16.48%). Multivariable logistic regression analysis showed that limited knowledge was significantly associated with the time since self-study of insulin injection techniques (95% confidence interval: 1.039–1.295; p = 0.008), lower interest in injection techniques (95% confidence interval: 0.476–0.706; p < 0.001), and the absence of additional certifications beyond a registered nursing license (95% confidence interval: 0.236–0.645; p < 0.001).

Conclusions:

Nurses’ knowledge of insulin injection techniques largely depends on individual initiative. Improving knowledge levels, offering organizational learning opportunities, and requiring continued education are necessary to ensure consistent knowledge improvement across the workforce.

Keywords

continuing education diabetes insulin injection technique knowledge nurses

Introduction

According to the International Diabetes Federation,¹ the global population of individuals with diabetes is steadily increasing and is projected to reach 783 million by 2045. Diabetes mellitus is a major public health issue that places a significant burden on patients. The World Health Organization has identified reducing this burden by 2025 as a priority health goal.² Japan has one of the highest numbers of patients with diabetes in the world, with many individuals undergoing insulin therapy.³ An appropriate insulin injection technique facilitates good glycemic control and prevents complications in patients with diabetes. Many literature reviews on insulin injection techniques, guidelines, and best-practice brochures have been published and widely disseminated to patients and healthcare providers worldwide. However, several studies have highlighted a significant gap between the recommended best practices in the guidelines and the actual practice of insulin injection techniques in clinical settings.^4–8 Lipohypertrophy and localized insulin-derived amyloidosis are among the many reported complications caused by improper insulin injection techniques.⁹ Errors in insulin injection techniques can cause these issues to develop in the skin and induce fluctuations in blood glucose levels.¹⁰ Previous studies have highlighted the need to re-educate patients on proper injection techniques to prevent subcutaneous nodules, and have reported an increasing number of intervention program initiatives.^7,11,12 The most recent FITTER Forward recommendations were published,¹³ emphasizing the critical importance of education provided by healthcare professionals.

Recently, the main causes of hospitalization among patients with diabetes in Australia have shifted from traditional diabetes-related complications to cancers and respiratory infections.¹⁴ In England, diabetes-specific complications are a major cause of morbidity and hospitalization among individuals with diabetes, representing a large proportion of overall hospitalizations; moreover, this proportion is rising, among other conditions.¹⁵ A United States report has indicated that the conditions responsible for the increased hospitalization rates among individuals with diabetes are more diverse than previously recognized.¹⁶ In Japan, the treatment of other diseases in hospitalized patients with diabetes is guided by the policy of the diabetes treatment system, and diabetologists are increasingly practicing outside the endocrinology department.¹⁷ Given this clinical background, patients increasingly receive diabetes-related care from nurses who do not work in specialized diabetes care wards.

Nurses are usually involved in educating patients about insulin injection techniques. Previous studies have highlighted that nurses’ knowledge of insulin injection is insufficient. For example, a study in Nepal revealed that after administering insulin, half of the nurses left the needle in the skin for <5 s, and more than 80% of nurses reused needles.¹⁸ Another study in Indonesia reported inconsistencies in healthcare professionals’ insulin injection techniques, emphasizing the urgent need for evidence-based teaching materials.¹⁹ Chinese nurses’ knowledge of insulin injection techniques was insufficient, with 35.19% receiving a poor questionnaire score. They achieved low correct answers on question items, including the correct interval between two injections at the same site (16.37%), insulin aspart type (38.41%), and post-withdrawal site management (38.93%).²⁰ Similarly, a Turkish study highlighted a shortage of nurses who could properly teach injection techniques.²¹ Globally, 42.8% of diabetes specialist nurses and 24.0% of general nurses are involved in providing insulin injection instruction.²¹ Research shows that patients tend to have lower glycated hemoglobin levels when they are instructed by diabetes specialist nurses than when they receive guidance from general nurses.⁵ Nurses with strong knowledge of insulin injection techniques contribute more to patient care and have a clear impact on patients. Diabetes specialist nurses in England have been shown to improve patient outcomes and cost-effectiveness; however, their capacity is insufficient to meet the growing demand. Due to disease complexity and new advancements in treatment, expecting generalist staff to maintain expertise in diabetes care is unrealistic.²²

Basic nursing education in Japan focuses on nursing students’ theoretical understanding of insulin types and administration methods; however, practical skills are not taught.²³ Therefore, nursing students are expected to individually develop practical proficiency after graduating and upon entering clinical practice. While diabetes specialist nurses can incorporate the latest information into their daily nursing practice, nondiabetes specialty nurses have a limited understanding of the subject derived solely from their basic nursing education courses and may struggle to update their knowledge.

Optimal glycemic control in hospitalized patients is also essential to control and delay the onset of other severe complications, such as cardiovascular diseases.²⁴ Therefore, the current state of the diabetes-related knowledge and skills of nurses outside diabetes-specific departments has begun to attract attention recently. While several studies have investigated diet, exercise, and medication related to diabetes care,^25,26 only a few have focused on insulin injection techniques. To improve nurses’ knowledge of insulin injection techniques, identifying the factors underlying their insufficient understanding of these techniques is essential. Although some studies have investigated the factors that influence nurses’ attitudes toward and knowledge of insulin injection techniques,^20,27 to our knowledge, this is the first study to explore the predictors of inappropriate insulin injection techniques among nurses to examine specific intervention strategies. Therefore, this study aimed to examine the current knowledge gaps among nondiabetes specialty nurses regarding insulin injection techniques and identify the factors influencing their limited knowledge.

Methods

Study design

This cross-sectional study evaluated factors related to the limited knowledge of insulin injection techniques among nondiabetes specialty nurses. The STROBE checklist, which is the standardized criteria for reporting cross-sectional studies, was followed.²⁸

Participants

Participants were recruited from hospitals across Japan using stratified sampling between September and December 2022. This study used specific criteria to investigate the actual circumstances of nurses working in hospitals that do not specialize in diabetes care. It targeted nurses with at least 1 year of hospital experience. Participants were informed that their participation was voluntary, they could withdraw from the study at any time, and submitting the anonymous questionnaire would be considered as providing consent to participate. Nurses with <1 year of practical nursing experience, diabetes specialist nurses, and certified diabetes nurses were excluded. The number of selected hospitals was determined based on the Survey of Medical Institutions and Hospital Reports.²⁹ We randomly selected 2400 facilities, stratified by the eight Regional Bureaus of Health and Welfare in Japan and number of beds (⩽300 or ⩾301 beds), from the list of national medical institutions (hospitals and clinics) published by the Institute for Healthcare Economics and Policy.³⁰

These facilities were approached to request the participation of their nurses in this study; five copies of the questionnaire were sent to each facility. Overall, 348 facilities cooperated, and 1740 copies of the survey were distributed. Each facility’s manager distributed the questionnaire to five nurses in the facility, along with a written request for research cooperation that included an explanation of the study’s purpose. Among these, 941 questionnaires were collected (54% response rate), with 815 valid responses. The sample of eligible participants was determined based on the minimum number of participants required for the regression, calculated using n = 100 + 50i, where i refers to the number of independent variables in the final model.³¹ Given the inclusion of 14 independent variables in the study design, the required sample size was calculated to be 800. The final sample was considered appropriate for the analysis.

Questionnaire development

A self-administered questionnaire was developed based on previous studies and discussions among researchers (Supplemental Material). We engaged in discussions with two nurses with diabetes certifications in Japan to assess its content validity. A pilot test was conducted with five nurses (0.5% of the final sample), and the results were used to revise the questionnaire in terms of layout, wording, relevance, and test-taker efficiency. The questionnaire took ~5–10 min to complete.

Clinical and demographic characteristics (eight items)

Data were also collected on nurses’ age, nursing experience, certification, position status, and the department in which they worked within the past 3 years.

Quiz on insulin injection techniques and related knowledge (fifteen items)

Fifteen questions were prepared, based on a survey conducted among Chinese nurses on their knowledge of and attitudes toward insulin injection techniques.²⁰ The questionnaire’s development was guided by the textbook for Certified Diabetes Educators of Japan³² and patient pamphlets on insulin pen products available in Japan to ensure its content was culturally appropriate and consistent with standard nursing education and practice within Japan. Five response options were provided, with only one correct answer, including an option indicating no knowledge.

Items influencing nurses’ knowledge of insulin injection techniques and diabetes care and management (sixteen items)

Alotaibi et al.³³ identified barriers to acquiring diabetes knowledge among nondiabetes specialty nurses and factors that influence their support. We focused on insulin injection techniques based on diabetes knowledge and developed questions referring to the previous literature³³ to determine factors that may hinder nurses’ acquisition of knowledge in this area. The pretest revealed a potential discrepancy between respondents’ understanding of diabetes care and their knowledge of insulin injection techniques. Specifically, the questionnaire was structured to inquire about insulin injection techniques and knowledge of diabetes. Sixteen questions were included in the questionnaire, although the required number of questions was eight as data. Answers were evaluated using a six-point Likert scale with options ranging from “6 = strongly agree” to “1 = strongly disagree.” For the internal consistency coefficient of these eight questions, the Cronbach’s alpha value for items influencing nursing techniques and diabetes care, and management was 0.689, indicating an adequate level of reliability.

Current practice of insulin injection technique (seven items)

Specific details were asked regarding the participants’ current frequency of implementation, instruction, and observation of insulin injection techniques, as well as the usual practice of insulin injection techniques.

Learning opportunities for and learning status of insulin injection techniques (three items)

Questions were asked about learning opportunities and methods for acquiring knowledge of current insulin injection techniques, the last time participants had received education on this topic, and the time elapsed since the last review (self-study) of insulin injection techniques.

Statistical analysis

All data were analyzed using IBM SPSS Statistics for Windows, version 30.0 (IBM Corp., Armonk, NY, USA). Descriptive statistics were used to identify low-scoring items in the insulin injection technique quiz. Respondents with low scores were defined as the group with limited knowledge of insulin injection techniques (low-scoring group). Participants were categorized based on their knowledge test scores to compare outcomes across distinct knowledge levels. Categorizing the knowledge score was considered appropriate and justifiable for the study’s purpose, and the knowledge quiz scores were deemed unsuitable for parametric analysis. Participants were categorized into tertiles based on their scores to allow for clinically meaningful comparisons across knowledge levels, an approach preferred over dichotomization because it better maintains statistical power. This approach was also preferred because dichotomization reduces statistical power and the ability to detect significant differences,³⁴ enabling comparisons between the lowest and highest groups and resulting in less efficacy loss than dichotomizing a normally distributed continuous variable.³⁵ Specifically, this categorization yielded a high-scoring (n = 204) and low-scoring (n = 182) group with scores of ⩾13 and ⩽8, respectively.

Age, years of nursing experience, education, job status certification other than registered nursing license, frequency of insulin injection practice, frequency of insulin instructions to patients, frequency of standby for ensuring accurate insulin injections, and time since last review (self-study) of insulin injection techniques were reported as mean ± standard deviation or number (percentage), as appropriate. Significant differences were considered at p < 0.05. Analysis was restricted to cases with complete data for all variables included. Those with missing values were excluded using listwise deletion. Data for age and nursing experience were analyzed using the t-test, whereas those on the departments in which the nurses worked, positions held, and certifications other than a registered nursing license were analyzed using Fisher’s exact test. Pearson’s chi-squared tests were conducted for data on education, frequency of insulin injection practice, frequency of insulin instruction to patients, frequency of standby for ensuring accurate insulin injections, time since the last review (self-study) of insulin injection techniques, and materials used for self-study to develop the techniques.

Multiple responses regarding the materials used for self-study of insulin injection techniques were collected and summarized using descriptive statistics. For items that influenced nurses’ knowledge of insulin injection techniques, a Mann–Whitney U test was performed to compare the low- and high-scoring groups. A logistic regression analysis was conducted using the low-scoring group as an explanatory variable. Nominal variables were processed as dummy variables. Before conducting the binary logistic regression analysis, the assumption of linearity between the log-odds and continuous predictor variables (age and years of experience) was assessed using interaction terms based on the Box–Tidwell procedure. No significant interaction terms were identified, indicating that the linearity assumption was met for these variables. Multicollinearity among predictors was assessed using variance inflation factors, all of which were below 5, indicating that multicollinearity was not a concern in the model. The discriminative ability of the multivariable logistic regression model was evaluated using the area under the receiver operating characteristic curve.

Ethics approval

This study was conducted in accordance with the principles of the Helsinki Declaration of 1975 as revised in 2024 and was approved by the Ethics Committee of Sapporo University of Health Sciences (1-15 Nishi 4-jo 2-chome, Nakanuma Nishi, Higashi-ku, Sapporo, Hokkaido, Japan; approval number: 022005-1) on June 20, 2022. All participants voluntarily participated in this study. Written information about the study was provided before participation, and informed consent was obtained through the voluntary completion and submission of the anonymous questionnaire. Participants were also assured of confidentiality and anonymity.

Results

Participant characteristics

Regarding the nurses’ educational background, 12.6% had a bachelor’s degree and 78.3% attended a professional training college, indicating that a smaller proportion of respondents had received basic nursing education at a university. No significant differences in education, job status, and frequency of insulin injection practice were found between the low- and high-scoring groups (Table 1). The variables that showed significant differences between the two groups were age (p < 0.001), years of nursing experience (p < 0.001), department (p < 0.001), certification other than a registered nursing license (p < 0.001), frequency of insulin instructions to patients (p < 0.001), frequency of standby for ensuring accurate insulin injections (p = 0.006), and time since the last review (self-study) of insulin injection techniques (p < 0.001).

Table 1.

Summary of participant characteristics and univariate analysis results (n = 815).

Variables	All (n = 815)	Low-scoring group (n = 182)	High-scoring group (n = 204)	p
Age (years)	39.00 ± 15.1	37.39 ± 10.81	41.32 ± 10.51	<0.001
Nursing experience (years)	15.12 ± 10.1	13.42 ± 10.00	17.23 ± 10.24	<0.001
Department
Endocrinology (including mixed departments)	187 (22.9%)	30 (16.5%)	66 (32.4%)	<0.001
Others	628 (77.1%)	152 (83.5%)	138 (67.6%)
Endocrinology (mixed departments including) within 3 years	245 (30.1%)	34 (18.7%)	90 (44.1%)	<0.001
Others	570 (69.9%)	148 (81.3%)	114 (55.9%)
Education				0.177
Professional training college	638 (78.3%)	141 (77.5%)	165 (80.9%)
Junior college	47 (5.8%)	8 (4.4%)	12 (5.9%)
Bachelor	103 (12.6%)	29 (15.9%)	17 (8.3%)
Master or above	8 (1.0%)	1 (0.5%)	5 (2.5%)
Other	18 (2.2%)	3 (1.6%)	9 (4.4%)
Positions held				0.905
Yes	194 (23.8%)	43 (23.6%)	47 (23.0%)
None	621 (76.2%)	139 (76.4%)	157 (77.0%)
Certification other than registered nursing licence
Yes	584 (71.7%)	21 (11.5%)	104 (51.0%)	<0.001
No	231 (28.3%)	161 (88.5%)	100 (49.0%)
Certified Diabetes Educator	136 (16.7%)	4 (2.2%)	81 (39.7%)
Frequency of insulin injection practice				0.619
More than twice a week	398 (48.8%)	92 (50.5%)	101 (49.5%)
More than once a week	148 (18.2%)	30 (16.5%)	35 (17.2%)
More than once a month	137 (16.8%)	31 (17.0%)	34 (16.7%)
More than once half a year	67 (8.2%)	18 (9.9%)	15 (7.4%)
About once a year	25 (3.1%)	6 (3.3%)	6 (2.9%)
None	40 (4.9%)	5 (2.7%)	13 (6.4%)
Frequency of providing insulin injection instructions to patients				<0.001
More than twice a week	63 (7.7%)	10 (5.5%)^a	30 (14.7%)^b
More than once a week	45 (5.5%)	6 (3.3%)^a	17 (8.3%)^b
More than once a month	191 (23.4%)	34 (18.7%)^a	56 (27.5%)^b
More than once half a year	252 (30.9%)	55 (30.2%)	59 (28.9%)
About once a year	129 (15.8%)	39 (21.4%)^b	15 (7.4%)^a
None	135 (16.6%)	38 (20.9%)^b	27 (13.2)^a
Frequency of standby for ensuring accurate insulin injections				0.006
More than twice a week	123 (15.1%)	20 (11.0%)^a	44 (21.6%)^b
More than once a week	89 (10.9%)	17 (9.3%)	22 (12.1%)
More than once a month	193 (23.7%)	38 (20.9%)	54 (29.7%)
More than once half a year	214 (26.3%)	49 (26.9%)	46 (25.3%)
About once a year	102 (12.5%)	31 (17.0%)^b	17 (9.3%)^a
None	94 (11.5%)	27 (14.8%)	21 (11.5%)
Time since self-study of insulin injection techniques				<0.001
<3 months ago	228 (28.0%)	32 (17.6%)^a	95 (46.6%)^b
3–6 months ago	116 (14.2%)	15 (8.2%)	29 (14.2%)
6–12 months ago	173 (21.2%)	45 (24.7%)	35 (17.2%)
1–3 years ago	159 (19.5%)	45 (24.7%)^b	28 (13.7%)^a
3–5 years ago	65 (8.0%)	21 (11.5%)^b	5 (2.5%)^a
More than 5 years ago	74 (9.1%)	24 (13.2%)^b	12 (5.9%)^a

Note. t-tests: age, nursing experience. Fisher’s exact tests: department, position, certification other than registered nursing licence. Pearson’s chi-squared tests: education, frequency of insulin practice, frequency of insulin instruction to the patient, frequency of standby for ensuring accurate insulin injections, time since previous self-study of insulin injection techniques.

Significantly less.

Significantly more.

Results of the insulin injection technique quiz

Table 2 summarizes the percentage of correct answers on the knowledge quiz for the overall audience and the high- and low-scoring groups. The high-scoring group had about 75% or more of the correct answers for each item, whereas the low-scoring group’s correct answers varied according to the question. In addition, the low-scoring group had particularly low percentages of correct answers to the question regarding the names of subcutaneous nodules at the injection site and injection timing of short-acting insulin, while the following two questions were answered in more than 75%: how long to keep the needle in the skin after insulin injection, and how to prime an insulin pen. Knowledge quizzes with lower scores tended to have a lower overall percentage of correct answers.

Table 2.

Accuracy rates in the insulin injection knowledge quiz.

No.	Questions	Accuracy rate (%)
No.	Questions	All (n = 815)	Low-scoring group (n = 182)	High-scoring group (n = 204)
1	Rate of insulin absorption according to injection site, rapid to slow	57.06	30.22	89.22
2	What is the insulin type of insulin aspart	69.08	32.97	96.57
3	When should short-acting insulin be injected?	45.77	22.53	75.98
4	Minimum distance of injection site from the last injection site	65.28	34.62	93.14
5	What is the name of a lump that forms at the injection site, one of the complications associated with insulin injections?	55.58	16.48	93.14
6	What causes the aforementioned “lumps?”	80.98	53.30	96.08
7	What are the adverse effects of the aforementioned “lumps?”	83.80	56.04	99.02
8	Describe the appropriate handling of the injection site after withdrawal of the insulin pen needle	61.84	52.20	73.04
9	Mistakes in managing hypoglycemia	73.01	50.00	91.18
10	What is the correct storage temperature for unopened insulin pen products?	83.19	67.58	95.10
11	Expiration date of pen insulin injections after opening	52.52	28.02	77.94
12	Which of the following is a correct reason not to inject an insulin pen product after taking it out of the refrigerator?	75.09	51.10	93.14
13	How long should the needle stay after insulin pen injection?	93.50	85.16	99.51
14	Proper mixing method for insulin pen before injection (choose the incorrect option)	66.01	37.36	91.67
15	Choose the correct option for preparing and priming insulin pens	86.13	77.47	95.59

Materials used for self-study of insulin injection techniques

Data on the materials used for self-study of insulin injection techniques were collected through multiple responses. Table 3 shows that most nurses depend on pharmaceutical companies’ procedures. The high-scoring group was characterized by participation in more workshops conducted by pharmaceutical companies. Furthermore, the utilization rate of workplace workshops and nursing reference books did not substantially differ between the two groups.

Table 3.

Materials used for self-study of insulin injection techniques (multiple answers possible).

Materials	All (n = 815)	Low-scoring group (n = 182)	High-scoring group (n = 204)	p
Procedures by pharmaceutical companies	503 (61.7%)	93 (51.1%)	149 (73.0%)	<0.001
Workshops at workplaces	301 (36.9%)	61 (33.5%)	76 (37.3%)	0.255
Workshops by pharmaceutical companies	193 (23.7%)	21 (11.5%)	79 (38.7%)	<0.001
Nursing reference books	272 (33.4%)	61 (33.5%)	58 (28.4%)	0.677
Articles from medical journals	157 (19.3%)	16 (8.8%)	62 (30.4%)	<0.001
Materials from professional organizations	105 (12.9%)	19 (10.4%)	43 (21.1%)	0.005
Internet	35 (4.3%)	8 (4.4%)	8 (3.9%)	1.000
Research papers	5 (0.6%)	0 (0%)	3 (1.5%)	0.09
E-learning	7 (0.9%)	0 (0%)	1 (0.5%)	0.45
Others	14	4	5

Note. Workshop at workplaces, reference papers, e-learning were analyzed using Fisher’s exact test. Other materials were analyzed using Pearson’s chi-squared tests.

Items on factors affecting insulin injection techniques

Table 4 presents a comparison of items on the factors affecting insulin injection techniques between the low- and high-scoring groups. Significant differences were identified for seven of the eight items between the two groups. The only item where the two groups did not significantly differ was whether learning other things was a higher priority than learning insulin injection technique.

Table 4.

Comparison of items affecting insulin injection technique by total scores on the insulin injection technique quiz.

Variables	All (n = 815)	Low-scoring group (n = 182)	High-scoring group (n = 204)	p
Gaining knowledge about insulin injection techniques is of interest to you	4.47 ± 0.95	4.00 ± 0.99	4.91 ± 0.84	<0.001
You have time to attend training on insulin injection techniques	3.40 ± 1.23	2.99 ± 1.14	3.79 ± 1.27	<0.001
Learning about other areas of expertise is a higher priority for you than learning about insulin injection techniques	3.89 ± 1.07	3.85 ± 1.10	3.79 ± 1.06	0.487
Your workplace has numerous opportunities for workshops, etc., on insulin injection techniques	2.45 ± 1.04	2.20 ± 0.97	2.75 ± 1.16	<0.001
Your workplace offers numerous opportunities to learn and work with more than just insulin injection techniques	4.23 ± 1.10	4.07 ± 1.16	4.38 ± 1.03	0.01
Your workplace is up-to-date on insulin injection techniques	3.06 ± 1.14	2.74 ± 1.10	3.40 ± 1.17	<0.001
Studying insulin injection techniques is recognized as career enhancement	3.39 ± 1.23	3.15 ± 1.20	3.65 ± 1.24	<0.001
Your workplace encourages communication with colleagues about insulin injection techniques	2.99 ± 1.18	2.69 ± 1.11	3.44 ± 1.16	<0.001

Note. Mann–Whitney U test.

Items exhibiting significant differences between the low- and high-score groups were selected as independent variables for binary logistic regression based on findings from the preliminary univariate analyses (Tables 1 and 4). The low-score group served as the dependent variable. Logistic regression analysis was conducted to examine whether the associations identified in the univariate analyses remained significant after adjusting for potential confounders. Table 5 presents the results of the regression analysis. Potential contributing factors were age, years of nursing experience, experience of working in the endocrinology department within the last 3 years, frequency of standing by to ensure accurate insulin injections, frequency of insulin instructions to patients, time since last review (self-study) of insulin injection techniques, interest in injection techniques, having time to attend training on insulin injection techniques, opportunities for workplace workshops; handling several tasks other than insulin injection techniques at the workplace; updating based on the insulin injection techniques offered at the workplace, studying insulin injection techniques for career enhancement, finding opportunities to discuss insulin injection techniques with colleagues, and having certification other than a registered nursing license.

Table 5.

Results of the logistic regression analysis of factors predicting low levels of knowledge of insulin injection techniques.

Variables	B	SE	Wald	p	Exp (B)	95% CI
Variables	B	SE	Wald	p	Exp (B)	Lower	Upper
Time since last review (self-study) of insulin injection techniques	0.149	0.056	7.006	0.008	1.160	1.039	1.295
Interested in learning injection techniques	−0.545	0.101	23.351	<0.001	0.580	0.476	0.706
Certification other than a registered nursing license	−0.942	0.257	13.419	<0.001	0.390	0.236	0.645
The AUC was 0.704 (95% CI: 0.633–0.745, p < 0.001).
Input variables
Frequency of standby for ensuring accurate insulin injections
Frequency of providing insulin instructions to the patient
Having time to attend training on insulin injection techniques
Handling several tasks other than insulin injection techniques at the workplace
Updates on insulin injection techniques offered in the workplace
Studying insulin injection technique enhances your career
Opportunity to discuss insulin injection techniques with colleagues
Experience working in the endocrinology department within the last 3 years
Opportunities for workplace workshop
Age
Nursing experience

AUC: area under the curve; CI: confidence interval.

Statistical analysis revealed the following factors affecting nurses’ limited knowledge of insulin injection techniques: the time since last review (self-study) of insulin injection techniques (p = 0.008; 95% confidence interval (CI): 1.03955–1.295), less interest in injection techniques (p < 0.001; 95% CI: 0.476–0.706), and lack of certifications other than a registered nursing license (p < 0.001; 95% CI: 0.236–0.645). The model’s discriminative ability was 0.74 (95% CI: 0.633–0.745, p < 0.001).

Discussion

We conducted a survey involving nondiabetes specialty nurses in Japan to identify their current state of knowledge of insulin injection techniques and factors that predict nurses’ limited knowledge of these techniques. The attributes examined in this study, including age, years of nursing experience, and job status, were similar to those assessed in a Japanese national survey.³⁶ Therefore, this study’s results are likely to be indicative of population characteristics. The results also indicate that the frequency with which nurses practiced insulin injection techniques remained consistent regardless of the presence or absence of correct knowledge. Several nurses in the high-scoring group had experience in the endocrinology department within the last 3 years. Endocrinology department nurses receive more knowledge and develop more skills related to insulin injections than non-endocrinology department nurses.²⁸ Takase et al. asserted that learning while working can improve nursing abilities.³⁷ Work experience and encounters, as well as relationships with people at work, influence the promotion of learning at work.³⁸ The presence of learning opportunities in the workplace indicates an environment that provides natural opportunities for nurses to learn and update their knowledge.³³ Therefore, endocrinology personnel are more familiar with the technical requirements of their specialty, and these nurses’ insulin injection knowledge could be better than that of non-endocrinology department nurses. However, insulin administration has become common across various hospital units with the increasing prevalence of diabetes, necessitating that nurses outside of specialized endocrinology departments should be proficient in basic insulin injection techniques. Enhancing the focus on insulin management within basic nursing education curricula is one potential approach to address this need. This is similar to the recent transition of topics such as disaster nursing from being minor subjects to becoming integral parts of nursing education, which are currently emphasized globally.³⁹

Maintaining nursing competency generally requires healthcare professionals to regularly update their skills and partake in continuing education or professional development.⁴⁰ Compared to countries such as the United Kingdom, the United States, Australia, and China, where mandatory nursing license renewal systems are in place, continuing education remains largely voluntary in Japan and is driven by individual motivation.^41–44 Although speculative, the finding from our logistic regression analysis, indicating that not holding qualifications other than a nursing license was an influencing factor for lower scores, reflects this context. A lower inclination toward continuous professional development, potentially influenced by the absence of mandatory systems, may contribute to fewer individuals pursuing additional qualifications and lower scores on fundamental skills assessments, such as the injection technique test used in this study. Most nurses worldwide rely on diverse continuing education activities such as clinical updates, competency assessments, e-learning modules, webinars, workshops, conferences, and specialty certifications to maintain their competency.⁴⁵ The present study results indicated that Japanese nurses primarily relied on materials developed for patients for self-study rather than resources specifically designed for continuing nursing education. Predictors associated with limited knowledge identified in the logistic regression analysis (Table 5) were time since last review (self-study) of insulin injection techniques, less interest in injection techniques, and having few certifications other than a registered nursing license. Interest is usually considered to be a process that contributes to learning and achievement.^46,47 The current state and impact of continuing education among nurses in Japan warrant further investigation. Nurses are typically responsible for their professional development in contexts where general nursing licenses are not subject to periodic renewal, as in Japan. While specialist and certified nurses are required to renew their certifications,⁴¹ the absence of a mandatory renewal system for general nurses underscores the need for attention to post-licensure continuing education. This includes implementing a license renewal system and developing standardized educational materials to support lifelong learning. Regarding the specific implementation format of mandatory continuing education, strategies with a high practical viability and quality assurance mechanisms, such as online continuing education modules with integrated assessment, should be deemed appropriate for nurses working in various settings and environments.

Items on the following knowledge-related themes were answered correctly at low rates in the low-scoring group: the names of subcutaneous nodules (16.48%), insulin aspart (32.97%), insulin absorption (30.22%), timing of injection of short-acting insulin (22.53%), and expiration date of pen insulin (22.02%). Focusing on improving performance on items where low-scoring nurses had low correct response rates could lead to an overall improvement in insulin injection techniques among Japanese nurses. The likely reasons for the low correct response rates noted for some questions could be surmised as follows. One possible reason for the low awareness of subcutaneous nodules among general clinical nurses is that the link between injection techniques and subcutaneous nodules only became known around the 2010s.^48,49 The accuracy rate for the question regarding the minimal distance of the injection site from the last injection site was also low (overall: 65.28%, low-scoring group: 34.62%). This is an injection technique used to prevent subcutaneous nodules.^50,51 Accuracy data from other countries on this question showed considerable variation; for instance, the rate was 51.1% and 88.1% in China and Nepal, respectively. The importance of this specific technique is highlighted in the latest international FITTER Forward recommendations, which emphasize its crucial role in optimizing glycemic control and preventing complications.¹³ The rate for the “timing of short-acting insulin injections” was also low in our sample, consistent with the findings of a study in Guangdong Province, China,²⁸ which reported correct rates of 36.3% and 38.0% for insulin aspart type and timing of short-acting insulin injections, respectively. Although the overall rate for “insulin aspart type” was relatively higher in our study, the significantly lower rate observed in the low-scoring group suggests that mastering this specific knowledge item remains challenging, highlighting it as a potential focus for targeted training. Furthermore, the markedly lower correct response rate for “expiration date of pen insulin after opening” (overall: 52.52%, low-scoring group: 28.02%) in the present study than the rate of 86% reported in a Chinese study²⁰ indicates a possible knowledge gap among Japanese nurses. This discrepancy may stem from differences in educational emphasis or clinical practices related to insulin handling. Nurses’ limited knowledge of insulin leads to an inadequate understanding of the pharmacological treatment of diabetes.⁵² Other studies have also shown that nurses have a low pharmacological understanding of insulin.^27,53 Accordingly, low pharmacological knowledge is one of the issues noted among clinical nurses with limited knowledge of insulin injection techniques, and their pharmacological knowledge, other than that of insulin in particular, is possibly also low. Therefore, strengthening this element in continuing education for nurses is highly recommended. The question regarding the absorption rate of insulin by the injection site may have been more challenging for general nurses, despite being described in the textbook for Certified Diabetes Educators of Japan.³² In a survey of Chinese nurses conducted by Wu et al.,²⁰ the accuracy rate for this question was high, at 81.85%; however, it was only 57.06% in the current survey. Although the abdomen is the usual choice of insulin injection site, the materials mainly explain the insulin injection site, but not the absorption rate of each of these sites.^5,54 The variation in correct answer rates across countries likely reflects the distinct practices and protocols inherent to each nation. These include specific regulations and commonly employed methods for administering injections, which are not globally uniform.

Table 3 summarizes the educational materials most nurses in the high-scoring group used to study insulin injection techniques, including workshops and procedures provided by pharmaceutical companies. In the future, making it easier for nurses outside of endocrinology departments to obtain knowledge related to insulin injection is necessary. Continuing education tools are increasingly shifting toward digital platforms, making it imperative for nurses to possess information and communication technology (ICT) skills to enhance their professional capabilities.⁵⁵ Even if workshops are not held at one’s workplace, e-learning allows for learning at one’s own pace compared to group education. Web-based education, as an intervention for a small number of participants, was found to increase nurses’ knowledge and competencies in diabetes management-related skills.⁵⁶ Developing ICT materials related to diabetes management skills that are accessible to all clinical nurses for continuing education is one of the most pressing issues in this field. In this domain, several educational materials for nurses have been developed, and their impact has been explored through intervention studies.^56–58 However, resources that specifically focused on practical injection techniques appear to be limited. As noted earlier, existing e-learning solutions primarily aim to assess theoretical knowledge rather than facilitate hands-on skills refinement. Consequently, approaches that enable the practice and improvement of practical skills, such as simulation-based training, and the development of artificial intelligence-powered learning materials tailored to each learner’s needs, represent crucial areas for future development and innovation in this field.⁵⁹

Strengths and limitations

To ensure sufficient statistical power and representativeness of the Japanese population, we employed stratified sampling to collect a nationwide sample. However, since this study focused solely on nurses working in Japanese hospitals, the findings may not be generalizable to other environments, specifically to low-resource hospitals or nurses working in home care settings. This study has some limitations related to the questionnaire. The internal consistency of the questionnaire was less than ideal (α = 0.689). Although the content validity and internal consistency were assessed, the questionnaire lacked comprehensive validation, such as factor analysis and criterion validity. As the response rate was 54%, selection bias in the respondents’ characteristics cannot be denied. However, considering the general response rate for mail surveys,⁶⁰ the data obtained can be considered sufficiently practical and meaningful. Furthermore, this study’s cross-sectional design limits the ability to draw causal inferences. Nurses’ injection skills were assessed using a questionnaire rather than based on practical skills assessments. Although questionnaires provide valuable insights, they may introduce subjectivity and potential biases, compared to direct skills assessments. Reliance on self-reported data introduces the potential for social desirability bias, possibly leading participants to over-report desirable behaviors, especially concerning self-assessed learning activities. Moreover, a multiple-choice response format was used in the questionnaire, and answering the questions correctly was possible without relevant knowledge or through guesswork. Future studies could consider incorporating practical assessments along with self-reported data for a more comprehensive understanding of participants’ skills.

Conclusion

Nurses with limited knowledge of proper insulin injection techniques administered insulin as frequently as those with more extensive knowledge. Several factors appeared to contribute to the lower knowledge levels observed in some nurses, including personal interests, which largely depended on individual initiatives. Therefore, providing organizational learning opportunities and mandatory continuing education is essential to enhance knowledge levels across this workforce.

Supplemental Material

sj-docx-1-smo-10.1177_20503121251367182 – Supplemental material for Predictors of limited knowledge in insulin injection techniques among non-specialty nurses in Japan

Supplemental material, sj-docx-1-smo-10.1177_20503121251367182 for Predictors of limited knowledge in insulin injection techniques among non-specialty nurses in Japan by Yuko Yoshida, Minoru Kikuchi, Norio Nakamura and Toshiko Tomisawa in SAGE Open Medicine

Footnotes

Acknowledgements

We thank the nurses and researchers who provided advice in developing the questionnaire, the facilities that helped distribute the questionnaire, and the nurses who participated in this study.

ORCID iD

Yuko Yoshida

Ethical considerations

This study’s protocol was conducted in accordance with the principles of the Declaration of Helsinki and was approved by the Ethics Committee of Sapporo University of Health Sciences (022005-1).

Consent to participate

All participants participated voluntarily in this study. Written information about the study was provided prior to participation, and informed consent was obtained by the voluntary completion and submission of the anonymous questionnaire. Participants were also assured of confidentiality and anonymity.

Author contributions

Conceptualization: Y.Y., T.T., M.K., N.N. Methodology: Y.Y., T.T., M.K. Data curation: Y.Y., T.T. Formal analysis: Y.Y. Investigation: Y.Y., T.T. Writing – original draft: Y.Y. Writing – review and editing: T.T., M.K., N.N. Supervision: T.T. Funding acquisition: Y.Y.

Funding

The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by JSPS KAKENHI grant number JP20K10572.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Data availability statement

All data generated or analyzed during this study are available from the corresponding author on reasonable request.

Supplemental material

Supplemental material for this article is available online.

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