Cap Insulin Prices Act This bill reduces cost-sharing for insulin under private health insurance and the Medicare prescription drug benefit. Specifically, the bill caps cost-sharing under private health insurance for a month's supply of selected insulin products at $25 or 25% of a plan's negotiated price (after any price concessions), whichever is less, beginning in 2024. The bill caps cost-sharing under the Medicare prescription drug benefit for a month's supply insulin products at $25 beginning in 2024. The current cap on insulin products under Medicare is $35 per month.