Generics fill 84.5% of Medicare Part D claims and account for 11.6% of the cost

Medicare's prescription drug program paid for 1.71 billion claims in 2024. Generic drugs accounted for 1.45 billion of them, or 84.5 percent, but for $33.5 billion of the program's $288.6 billion in total drug costs, or 11.6 percent, according to the Part D grand totals report¹ that CMS publishes with its prescriber data.

In 2013, the first year in the series, generics were 76.0 percent of claims and 24.7 percent of costs.

Those two lines have moved in opposite directions every year but one since then, and in 2024 the cost line dropped faster than at any point in the record. The year-by-year numbers, from CMS's own totals, show where Part D money goes, how much of the shift comes from brand prices, and a 2024 fall in generic spending that lines up with a federal rule change on how pharmacy prices are recorded.

Where the numbers come from

CMS builds its Part D Prescribers datasets⁴ from prescription drug event records, the claim summaries plans submit for every Part D fill. The grand totals are not limited by the privacy suppression in the detailed files; the report says it is "aggregated based on all Medicare Part D PDE data, excluding over the counter prescriptions."

CMS sorts claims into brand, generic and other by FDA application type. CMS's data dictionary³ classifies a drug as generic if it was approved under an Abbreviated New Drug Application (ANDA). Brand covers drugs approved under a New Drug Application, NDA authorized generics, and biologics licensed under a Biologics License Application. Everything else is "other," which was 0.7 percent of claims in 2024. Under this rule an authorized generic counts as brand, even though pharmacies and patients treat it as a generic.

Drug cost "includes ingredient cost, dispensing fee, sales tax, and any applicable vaccine administration fees," per the dictionary, and covers amounts paid by plans, beneficiaries, government subsidies and other payers. It does not subtract manufacturer rebates. CMS's Part D spending methodology⁶ says the agency "is prohibited from publicly disclosing such information."

Twelve years of Part D claims and costs

Source: CMS Medicare Part D Prescribers grand totals, calendar years 2013 to 2024¹. Shares and averages are GxRadar calculations from the report's claim and cost columns.

Beneficiaries with at least one Part D claim rose from 35.1 million in 2013 to 53.2 million in 2024 in the same report, so part of the claim growth reflects a larger program.

Brand costs more than tripled while brand claims fell

Brand claims dropped from 316 million in 2013 to 253 million in 2024, a fall of 20 percent. Brand costs rose from $77.7 billion to $253.9 billion. The average brand claim went from $246 to $1,003.

Generic claims, meanwhile, grew 39 percent, from 1.04 billion to 1.45 billion. Generic costs grew 31 percent over the same span, from $25.6 billion to $33.5 billion, and the average generic claim stayed between $23 and $30 in every year of the series. That stability is the program-level view of the pharmacy-cost declines GxRadar follows in the long deflation of generic prices.

So generics fill a growing majority of Part D prescriptions while taking a shrinking slice of the cost. HHS researchers made a similar point at the national level: a January 2025 ASPE issue brief⁹ estimated that 91 percent of all US prescriptions in 2022 were filled as generics.

The 2024 drop in generic spending

From 2023 to 2024, generic claims rose 6.2 percent while total generic cost fell 15.8 percent, from $39.8 billion to $33.5 billion. The average generic claim fell from $29.25 to $23.19.

Drug by drug, the drop looks similar. The table below uses CMS's Part D Spending by Drug⁵ file for the most-used products listed under their generic names. Spending per claim is gross of rebates, as with the totals above.

CMS's files do not attribute the decline to a cause. It does coincide with a rule CMS finalized in May 2022. That Federal Register rule⁷ redefined a drug's "negotiated price" in Part D as "the lowest possible reimbursement" a network pharmacy will receive, "taking into account pharmacy price concessions," and made the change applicable beginning Jan. 1, 2024. Before then, many pharmacy price concessions were collected after the sale and did not appear in the claim price. Moving them to the point of sale would lower the recorded cost of a fill. GxRadar has not tested that link claim by claim. Pharmacy payment mechanics are covered in how pharmacies get paid for a prescription.

What these totals leave out

Three caveats apply. The totals are before manufacturer rebates, which CMS does not publish by drug, so the net brand and generic split is unknown. They include enrollee cost sharing, which changed under the Inflation Reduction Act; GxRadar covers the 2025 out-of-pocket cap and later changes in Medicare Part D changes in 2025, 2026 and 2027 and the Inflation Reduction Act and generic drugs. And the brand-generic split follows FDA application type, so the line falls slightly differently than it would on a pharmacy shelf. GxRadar's explainer on how Part D pays for generics covers the payment side.

What comes next

The Part D Prescribers methodology² says each year's data include claims received through June 30 of the following year, and CMS posted the 2024 totals in spring 2026. More detail is due later. Under section 6224 of the Consolidated Appropriations Act, 2026⁸, the federal PBM law enacted Feb. 3, 2026, pharmacy benefit managers working for Part D prescription drug plan sponsors must, beginning July 1, 2028, report for each drug the claims, dispensing channel, rebates and the average National Average Drug Acquisition Cost, the federal survey of pharmacy invoice prices. Those reports go to plan sponsors and to HHS, which will then hold drug-level Part D payments alongside the pharmacy acquisition benchmark.