In 2026, 55% of eligible Medicare beneficiaries are enrolled in a Medicare Advantage (MA) plan, according to KFF's June 2026 analysis of CMS enrollment files. That is 35.2 million of the 64.2 million people who have both Medicare Part A and Part B, up from 19% in 2007.
The share has changed little since 2023, but the plan mix keeps moving. Special needs plans grew fastest, and two insurers hold 46% of enrollment.
How large is Medicare Advantage in 2026?
KFF counted 35.2 million MA enrollees in March 2026. Enrollment grew by about 1.1 million people, or 3%, from 2025 to 2026. The prior year's growth rate was 4%. The CMS data KFF uses show 22 million MA enrollees in 2019 and 33 million in 2024, so the program added about 11 million people in five years.
The Congressional Budget Office projects that the MA share will reach 63% by 2034 and stay at 63% in 2035 and 2036, KFF reports. A practice whose Medicare panel is 55% MA today can plan for roughly 8 more points of MA share over the coming years.
| Plan type | 2026 enrollment | Share of MA enrollment | Comparison |
|---|---|---|---|
| Individual plans open to general enrollment | 21.4 million | 61% | 62% in 2025, 71% in 2010 |
| Special needs plans (SNPs) | 8.2 million | 23% | 21% in 2025 |
| Employer and union group plans | 5.7 million | 16% | Down about 31,000 from 2025 |
Source: KFF, "Medicare Advantage in 2026: Enrollment Update and Key Trends," published June 5, 2026 and updated July 1, 2026. Enrollment is as of March 2026.
Group plans, at 16% of MA, have the lowest share since 2010. Individual plans still hold most of the market, but their share has dropped 10 points since 2010.
Where the growth comes from
Special needs plans drove 85% of the net enrollment gain in 2026. In the prior year they drove 48%. SNPs enroll people with specific needs, and they now cover about 8.2 million people, or 23% of all MA enrollees.
Within SNPs, dual-eligible plans (D-SNPs) hold 78% of enrollment, down from 83% in 2025. Chronic condition plans (C-SNPs) hold 20%, up from 16%. C-SNP enrollment reached about 1.7 million, a rise of roughly 45%, or about 518,000 people. Institutional plans (I-SNPs) hold 2%, or about 124,000 people.
SNP share varies by state. KFF reports that SNPs make up 51% of MA enrollment in the District of Columbia, 46% in Mississippi, 40% in Arkansas and 37% in New York. In New Hampshire the share is 2%, and Alaska and Vermont have no SNP enrollment. A practice in Mississippi and a practice in New Hampshire face very different MA populations, with different coverage rules and care needs.
Which insurers hold the shares
UnitedHealth Group holds 26% of MA enrollment, or 9.3 million people, down from 29%. Humana holds 20%, or 7 million, up from 17%. Together they hold 46%, the same combined share as in 2025. CVS Health holds 12%, Kaiser Foundation Health Plan 6% and Elevance Health 5%.
KFF measured the change from March 2025 to March 2026. Humana added about 1.3 million enrollees, the largest gain. Devoted Health added about 258,000 and SCAN Group 136,000. UnitedHealth Group lost nearly 647,000, Elevance lost 346,000 and CVS lost nearly 29,000.
Local shares can be far higher than national shares. In 889 counties, or 28% of all counties, UnitedHealth Group and Humana together hold at least 75% of MA enrollment. KFF lists East Baton Rouge, Louisiana at 81%, Travis County, Texas at 78%, Jackson County, Missouri at 76% and Palm Beach, Florida at 75%.
The average Medicare beneficiary can choose among plans from 8 parent organizations in 2026, the same as in 2025 and 2024. About 29% of beneficiaries can choose among plans from 10 or more parent organizations. For a practice, the count that matters is the number of MA plans in its own county, because a few contracts can cover most of its MA patients.
How much prior authorization work comes with MA
KFF's January 28, 2026 analysis of CMS reporting files found that MA insurers made 52.8 million prior authorization determinations in 2024. Of those, 4.1 million, or 7.7%, were denied in full or in part. The denial rate was 6.4% in 2023 and 7.4% in 2022. About 99% of MA enrollees were in plans that require prior authorization for some services.
| Year | Requests per MA enrollee | Share denied in full or part |
|---|---|---|
| 2022 | 1.7 | 7.4% |
| 2023 | 1.8 | 6.4% |
| 2024 | 1.7 | 7.7% |
Source: KFF, "Medicare Advantage Insurers Made Nearly 53 Million Prior Authorization Determinations in 2024," January 28, 2026. Figures cover service determinations, not claim payment.
In 2024, 11.5% of denied requests were appealed, close to the 11.7% in 2023 and above the 7.5% in 2019. Of the appeals filed in 2024, 80.7% were fully or partly overturned. KFF found that more than 80% of appeals were overturned in every year from 2019 to 2024.
Traditional Medicare uses prior authorization far less. CMS completed 628,243 reviews in fiscal year 2024, about 2 per 100 beneficiaries. MA insurers averaged 1.7 determinations per enrollee, which is about 170 per 100.
Turning the figures into a payer-mix check
These are national averages, and a practice sees only the requests tied to its own orders. The arithmetic below shows the scale and does not predict any one practice's counts. Take a panel of 2,000 Medicare patients. At the national 55% share, about 1,100 are in MA. At the CBO's 63% projection for 2034, about 1,260 would be.
Apply the KFF averages to 1,000 MA patients. At 1.7 determinations per enrollee, that is 1,700 determinations in a year. At a 7.7% denial rate, about 131 are denied. At an 11.5% appeal rate, about 15 of those denials are appealed, and at 80.7%, about 12 of the appeals are fully or partly overturned. Most of the 131 denials are never appealed.
Two counts from the practice's own billing system make the comparison concrete. The first is MA patients as a share of Medicare patients, to set against 55%. The second is the number of MA plans that cover most of those patients, to set against the 8 parent organizations the average beneficiary sees.
Sources
- KFF, Medicare Advantage in 2026: Enrollment Update and Key Trends, June 5, 2026 (updated July 1, 2026)
- KFF, Medicare Advantage Insurers Made Nearly 53 Million Prior Authorization Determinations in 2024, January 28, 2026
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