How Medicare Advantage plans work
A Medicare Advantage plan (Part C) is a way to get your Medicare Part A and Part B benefits through a private plan that Medicare approves, instead of through Original Medicare. Here is what changes, when you can join or leave, and how many people choose it.
- What it is: you still have Medicare. You join a private plan that must cover everything Original Medicare covers (medically necessary services), and most plans add drug coverage and extras like some vision, hearing and dental.
- What you give up or accept: a network of doctors in many plans, possible referrals and prior authorization, and you cannot buy Medigap to cover a Medicare Advantage plan's costs.
- What you gain: a yearly limit on what you pay for covered Medicare services; Original Medicare has no yearly limit unless you add other coverage.
- When you can switch: Oct 15 to Dec 7 each year; plus Jan 1 to Mar 31 if you are already in a Medicare Advantage plan; plus special situations.
- How common: CMS counts 36,177,750 people (51.1%) in Medicare Advantage and other health plans in July 2026.
Last verified October 22, 2026 against Medicare.gov pages and the CMS July 2026 enrollment file. We do not recommend a plan or a company.
Original Medicare vs. a Medicare Advantage plan
Medicare.gov says there are two main ways to get Medicare coverage. Original Medicare includes Part A (hospital) and Part B (medical). A Medicare Advantage plan (Part C) includes both, from a private company approved by Medicare. The comparison below follows Medicare.gov's own table. Click a column to sort.
| Topic | Original Medicare | Medicare Advantage plan |
|---|---|---|
| Doctors and hospitals | Any doctor or hospital that takes Medicare, anywhere in the U.S. | In many plans you use the plan's network and service area for non-emergency care; some plans cover out-of-network at higher cost. |
| Referrals | In most cases no referral to see a specialist. | You may need a referral. |
| Prior approval | In most cases no prior authorization. | You may need approval from the plan before certain services or supplies. |
| Cost sharing | For Part B services you usually pay 20% after the deductible. | Plans set their own copays and coinsurance for services. |
| Yearly out-of-pocket limit | No limit unless you have supplemental coverage or other insurance (Medigap, Medicaid, employer or union coverage). | Plans have a yearly limit on what you pay for covered Medicare services. After it, you pay nothing for covered services for the rest of the year. |
| Premiums | Monthly Part B premium; a separate Part D premium if you add drug coverage. | You pay the Part B premium and may also pay the plan's premium. Some plans have a $0 premium. |
| Drug coverage | Join a separate Part D plan (optional). | Most plans include Part D; in most types you cannot join a separate drug plan. |
| Extra benefits | Does not cover some services, such as routine physical exams, eye exams and most dental care. | Plans must cover all medically necessary services Original Medicare covers, and may add benefits like some vision, hearing and dental. |
| Medigap | You can buy a Medigap policy to help with out-of-pocket costs. | You cannot buy Medigap to cover a Medicare Advantage plan's out-of-pocket costs. |
| Care outside the U.S. | Generally not covered; some Medigap policies cover emergency care abroad. | Generally not covered; some plans offer an extra benefit for emergency and urgent care when traveling. |
Plan types
Medicare.gov lists these Medicare Advantage plan types: Health Maintenance Organizations (HMOs), Preferred Provider Organizations (PPOs), Special Needs Plans (SNPs), Medicare Medical Savings Account (MSA) plans and Private Fee-for-Service (PFFS) plans. Separately, Medicare Cost Plans, demonstration/pilot programs and PACE are other Medicare health plans that are not Medicare Advantage plans.
When you can join, switch or drop
You can only join, switch or drop a Medicare Advantage plan during certain enrollment periods. In general you must have Part A and Part B, live in the plan's service area, and be a U.S. citizen or lawfully present.
| Enrollment period | When | What you can do |
|---|---|---|
| Initial Enrollment Period | Generally around turning 65: 7 months, starting 3 months before the month you turn 65 and ending 3 months after. | Join any plan. You need Part A and Part B to join a Medicare Advantage plan. |
| First 3 months of Medicare | Within the first 3 months you have Parts A and B, if you joined a Medicare Advantage plan in your initial period. | Switch to another MA plan or return to Original Medicare. |
| Open Enrollment Period | October 15 to December 7 | Join, drop or switch an MA plan, or switch between Original Medicare and MA. Coverage starts January 1 (the plan must get the request by December 7). |
| Medicare Advantage Open Enrollment Period | January 1 to March 31 (only if you are already in an MA plan) | Switch to another MA plan, or drop it and return to Original Medicare (you can also join a separate drug plan). Coverage starts the first of the month after the plan gets the request. |
| Special Enrollment Period | Varies | Only for certain life situations, such as moving, losing or changing coverage, getting Medicaid, or getting Extra Help with drug costs. |
Rules worth knowing
- Availability changes yearly. Insurers decide whether a plan is offered statewide or in certain counties, and each year they can join or leave Medicare. If your plan stops, you join another plan or return to Original Medicare.
- Disenrollment. A plan can disenroll you for reasons such as moving outside its service area, losing Medicare or Medicaid eligibility, or the plan's contract with Medicare ending. You then get a grace period and a Special Enrollment Period.
- Employer or union coverage. Medicare.gov warns that joining a Medicare Advantage plan might cause you to lose employer or union coverage, and that dropping it for yourself may also end coverage for your spouse and dependents. Talk to your benefits administrator first.
- Medigap. Medicare.gov says you cannot buy a Medigap policy to cover a Medicare Advantage plan's out-of-pocket costs.
How many people are in Medicare Advantage
CMS publishes monthly national counts. Its column is “Medicare Advantage and other health plans,” which also includes cost plans and similar programs. In July 2026 it was 36,177,750 of 70,736,624 beneficiaries, or 51.1%, up from 28.3% in July 2013. The share is our division of CMS's two columns.
| Month | Total Medicare beneficiaries | Original Medicare | Medicare Advantage and other health plans | Share in MA and other plans |
|---|---|---|---|---|
| July 2026 | 70,736,624 | 34,558,874 | 36,177,750 | 51.1% |
| July 2025 | 69,502,431 | 34,073,820 | 35,428,611 | 51.0% |
| July 2024 | 68,040,962 | 33,886,018 | 34,154,944 | 50.2% |
| July 2023 | 66,552,898 | 34,316,441 | 32,236,457 | 48.4% |
| July 2022 | 65,142,983 | 35,233,932 | 29,909,051 | 45.9% |
| July 2021 | 63,950,718 | 36,325,958 | 27,624,760 | 43.2% |
| July 2020 | 62,871,682 | 37,751,312 | 25,120,370 | 40.0% |
| July 2019 | 61,557,482 | 38,566,248 | 22,991,234 | 37.3% |
| July 2018 | 60,028,769 | 38,648,916 | 21,379,853 | 35.6% |
| July 2017 | 58,534,001 | 38,703,727 | 19,830,274 | 33.9% |
| July 2016 | 57,033,959 | 38,621,382 | 18,412,577 | 32.3% |
| July 2015 | 55,528,637 | 38,014,733 | 17,513,904 | 31.5% |
| July 2014 | 54,060,578 | 37,756,735 | 16,303,843 | 30.2% |
| July 2013 | 52,466,118 | 37,618,358 | 14,847,760 | 28.3% |
Free help
Medicare.gov says to contact your local State Health Insurance Assistance Program (SHIP) for free personalized health insurance counseling, and that SHIPs are not connected to any insurance company or health plan. To talk to Medicare directly, Medicare.gov lists 1-800-MEDICARE (1-800-633-4227), TTY 1-877-486-2048, on its Talk to someone page. Your Area Agency on Aging can also point you to local counseling. See also when to enroll in Medicare.
Method
Plan rules and dates are from the Medicare.gov pages named in the cite box, read on October 22, 2026. Enrollment is the CMS Medicare Monthly Enrollment national file (July 2026 release); the code checked that Original Medicare plus MA-and-other equals total for each month shown, and computed the share. Medicare rules and plan details change every year; verify at Medicare.gov before you decide.
Cite this page
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Primary sources
- Medicare.gov: Compare Original Medicare & Medicare Advantage — comparison table
- Medicare.gov: Joining a plan — enrollment periods
- Medicare.gov: Your health plan options — plan types, disenrollment
- Medicare.gov: Your coverage options — overview
- CMS: Medicare Monthly Enrollment, July 2026 release (data.cms.gov) — national rows, month of July, 2013 to 2026
The Retirement Literacy Foundation is a nonprofit and sells nothing here. Programs and rules change; confirm details with the agency named on the linked page. It does not endorse any plan, carrier or agent. General education, not individualized advice.