Impact of Insulin Copay Caps on Medicare Beneficiary Health and Spending

In this update, we highlight a JAMA Internal Medicine article that analyzed the real-world impact of insulin copay caps on Medicare beneficiaries with type 2 diabetes. According to a new study, these policies have successfully lowered out-of-pocket insulin costs and improved adherence among existing users, yet they have not increased the number of patients starting insulin therapy.

Spending Drops Sharply, Yet Total Costs Remain Flat

Following the 2021 CMS Innovation Center Part D Senior Savings Model and the 2023 Inflation Reduction Act’s nationwide insulin copay caps, mean quarterly out-of-pocket spending on insulin fell by $47.90 and then by an additional $58.59. However, rising costs for noninsulin diabetes medications offset these savings, resulting in no net change in overall out-of-pocket spending across all diabetes drugs.

Improved Glycemic Control Comes with Increased Hypoglycemia Risk

Among patients already using insulin, the quantity dispensed increased after both policy changes. This rise in utilization was associated with better glycemic control in a linked cohort of more than 207,000 patients. At the same time, the study recorded a modest increase in hypoglycemic events, highlighting the clinical trade-offs of greater insulin exposure.

Policy Helps Current Users Far More Than Insulin-Naïve Patients

Despite meaningful cost reductions, the proportion of Medicare beneficiaries using insulin did not grow during the study period. A slight decline in total insulin users was even observed after 2021. These findings suggest that insulin copay caps primarily benefit adherent patients rather than overcoming barriers faced by those who have never initiated insulin.

Need for Complementary Strategies Beyond Cost-Sharing Limits

The serial cross-sectional analysis of 4.8 million Medicare Part D beneficiaries from 2019 to 2023 demonstrates that while capping copays at $35 per month improves short-term clinical metrics for current users, it is insufficient alone to expand insulin initiation.

Read the full study in JAMA Internal Medicine

From a health economics perspective, future policy design and outcomes research must address substitution effects, incorporate long-term outcomes such as hospitalizations and cardiovascular events, and pair insulin copay caps with targeted education and prescriber support to reach insulin-naïve patients.