Objective Blue Cross and Blue Shield of Louisiana (BCBSLA) launched a zero-dollar co-pay (ZDC) pharmacy benefit on July 1, 2020, to reduce cost-related barriers to diabetes medications. This study evaluated the program’s effect on antidiabetic medication adherence and use patterns. Research Design and Methods We conducted a retrospective cohort study using BCBSLA medical and pharmacy claims from 2019–2021. The study included 7,603 continuously enrolled members with diabetes: 3,045 fully insured members with ZDC coverage (ZDC group) and 4,558 administrative-services-only members without ZDC coverage (control group). Follow-up was July 1, 2020, to December 31, 2021. Outcomes included monthly proportion of days covered (PDC), drug counts, and monthly medication use. We applied propensity score odds weights and estimated weighted difference-in-differences models with individual and time fixed effects, adjusting for demographics, comorbidities, healthcare utilization, and spending. Subgroup analyses examined pre-ZDC users, pre-ZDC non-users, and complex users. Results Mean age was 48.8 (SD 12.5) years in the ZDC group and 52.9 (SD 11.3) years in controls; 57.4% and 55.6% were female, respectively. The ZDC program increased PDC by 4.4 percentage points (p<0.001), monthly medication use by 6.2 percentage points (p<0.001), and drug counts by 0.090 (p<0.001). For ZDC-eligible medications, increases were 5.4 percentage points for PDC, 7.6 percentage points for monthly use, and 0.074 for drug counts (all p<0.001). Improvements were observed among pre-ZDC users and complex users, but not among pre-ZDC non-users. Conclusion A zero-dollar co-pay pharmacy benefit improved antidiabetic medication adherence and increased medication use among BCBSLA members with diabetes.
Tang et al. (2026) studied this question.