Background: Patients with HIV often have multiple medications besides antiretrovirals (ARV). Medication regimen complexity—formulations, dosing frequencies, and additional directions—expands pill burden by considering self-care demands. Studies show an inverse association between ARV adherence and medication complexity for ARVs only. Patient-level medication regimen complexity beyond ARV complexity is unknown. Objective: To measure and characterize Patient-level Medication Regimen Complexity Index (pMRCI) and Antiretroviral Medication Regimen Complexity Index (ARCI) for patients in 2 HIV clinics. We hypothesized that an all-medication complexity metric will exceed disease-state-defined complexity metrics; for ARVs only, the pMRCI score will be smaller than the ARCI score by capturing fewer features of regimens. Associations between complexity and adherence were not assessed. Method: Electronic records supplied a retrospective, random sample of adult patients with HIV; medication lists were used to code the pMRCI (n=200). A random subsample (n=66) was coded using ARCI for ARV regimens only. Result: Medication counts ranged from 1 to 27; pMRCI scores ranged from 2 to 67.5. ARVs contributed roughly 25% to the pMRCI; other prescriptions contributed about 66%. Dosing frequency made the largest contribution of all components (62%) to the pMRCI. For ARVs, pMRCI and ARCI scores did not differ statistically. Conclusion: Unique dosing frequencies raised complexity and may provide opportunities for intervention. Other prescriptions drove pMRCI scores, suggesting that HIV management programs should review all medications. A patient-level approach added value to understanding the role of medications in patient complexity; future work can assess association of pMRCI with adherence and patient outcomes.