When insulin becomes unaffordable, patients face an impossible choice: pay for the medication that keeps them alive, or skip doses to stretch their supply. That grim calculation is changing for some Americans, thanks to a $35 monthly cap on insulin for Medicare beneficiaries that took effect in 2023 under the Inflation Reduction Act.
A new study published in JAMA reveals the real-world impact of that policy, and the results are encouraging—though incomplete. Researchers from Emory University, the University of Southern California, and the University of Wisconsin–Madison analyzed data from more than 2.8 million Medicare Part D beneficiaries using insulin before and after the cap was introduced. What they found was measurable progress for a vulnerable subgroup, but a stark reminder that even landmark policies have limits.
The numbers tell a story of relief, especially for those who needed it most. Across the entire study cohort, average out-of-pocket insulin costs dropped by about 21 percent—roughly $5 per 30-day supply. More tellingly, costs became predictable; previously, some patients faced their insulin prices doubling within a single calendar year. For roughly 250,000 people who paid at least $58 for a 30-day supply before the cap, the impact was more dramatic: insulin fills increased by 8 percent, and the proportion of days when medication was available rose by 5 percent. Those aren't flashy numbers, but they represent people with diabetes actually taking their prescribed doses instead of rationing.
The mechanism behind this improvement is sobering. As Rebecca Myerson, an associate professor of health policy and management at Emory's Rollins School of Public Health, explains: "Insulin users who previously faced high insulin costs improved their adherence to insulin after the cap, suggesting they had been skipping doses to save money." When patients skip doses to stretch their supply, they risk serious complications—hospitalization, kidney damage, vision loss, and worse. The fact that lower costs translated to higher adherence suggests the policy addressed a real, dangerous problem.
But the study also exposes the policy's blind spots. Only 13 percent of insulin fills would have exceeded the $35 cap in 2021–2022, meaning most Medicare beneficiaries were already paying less. These patients represent the nation's better-insured population; many had already benefited from other affordability programs like Medicare's Senior Savings Model or Low-Income Subsidy Program. Those who did benefit most from the cap tended to be disproportionately non-Hispanic white, male, between 65 and 75 years old, with fee-for-service insurance and living outside urban areas—a narrow slice of the American insulin-dependent population.
The researchers point toward what could come next. A universal $35 cap applied to all insulin prescriptions in the United States—not just those covered by Medicare—would have saved insulin users $170 million in out-of-pocket costs in 2024 alone, according to data from The IQVIA Institute. As Dana Goldman, founding director of the USC Schaeffer Institute, notes: "Making sure patients take their medication should be a greater clinical priority. This research demonstrates a powerful policy lever for doing so: reducing their out-of-pocket costs."
The cap's success with high-cost users shows what's possible when policy directly addresses affordability. Yet its limited reach underscores an urgent truth: millions of uninsured and underinsured Americans still face the same impossible choice. The next generation of insulin policy must extend that lifeline further.