Turning 65 and Medicare: Complete Enrollment Guide (2025)
Turning 65 is one of the most important financial and health-care milestones in your life. Your Medicare decisions — made in a 7-month window around your 65th birthday — can affect your premiums, coverage, and costs for the rest of your life. This guide walks you through everything you need to do, in the right order.
Your 7-Month Initial Enrollment Period (IEP)
When you turn 65, you receive a one-time Initial Enrollment Period (IEP) — a 7-month window to sign up for Medicare. Miss this window without a qualifying reason, and you face permanent late enrollment penalties and gaps in coverage.
Your 7-Month IEP Window
- 3 months before your birthday month
- The month you turn 65
- 3 months after your birthday month
Example: If your birthday is June 15, your IEP runs April 1 through September 30.
Born on the 1st of the Month? Your IEP Starts a Month Earlier
If you were born on the first day of any month, Social Security considers you to have "turned" that age the month before. This means your Medicare eligibility begins one month earlier than it would for someone born later in the month — and your IEP starts four months before your birthday month rather than three.
Example: If your birthday is July 1, you are eligible for Medicare starting June 1, and your IEP begins March 1 (four months before June).
When to Enroll for Coverage Starting on Your 65th Birthday
The timing of your enrollment within the IEP affects when coverage begins:
- Enroll in months 1–3 of IEP (before your birthday month): coverage begins the month you turn 65
- Enroll in your birthday month: coverage begins the following month
- Enroll in months 5–7 of IEP (after your birthday month): coverage is delayed 2–3 months from enrollment
For the smoothest coverage transition with no gaps, enroll during the first three months of your IEP — the months before your birthday month.
The Medicare Decision Tree: Step by Step
Before signing up for anything, work through these steps to determine exactly what actions you need to take and when.
Step 1: Are you currently receiving Social Security benefits?
If YES: You are automatically enrolled in Medicare Part A and Part B. Your Medicare card will arrive approximately 3 months before your 65th birthday. Skip to Step 4 to decide between Original Medicare and Medicare Advantage.
If NO: You must actively enroll. Continue to Step 2.
Step 2: Are you working and covered by an employer group health plan (GHP)?
If YES, and the employer has 20 or more employees: Your employer GHP is primary, Medicare is secondary. You may safely delay Part B enrollment without penalty. You should still enroll in Part A at 65 (it is free for most people and has no downside, unless you are contributing to an HSA). When you eventually leave that employer coverage, you will have an 8-month Special Enrollment Period to sign up for Part B penalty-free.
If NO, or employer has fewer than 20 employees: Medicare is primary. You need to enroll. Continue to Step 3.
Step 3: Are you covered by COBRA, an ACA Marketplace plan, or retiree insurance?
WARNING — none of these count for delaying Medicare:
- COBRA: COBRA is continuation of former-employer coverage — it is not active employer GHP coverage. It does not qualify for a Medicare delay. Enroll during your IEP.
- ACA Marketplace plan: Marketplace plans are not employer GHP coverage. Once you are Medicare-eligible, you generally cannot receive premium tax credits and should enroll in Medicare during IEP.
- Retiree insurance: Most retiree health plans (other than FEHB) are not active employer GHP coverage and do not qualify for a Medicare delay. Enroll during your IEP and let Medicare become primary.
Step 4: Enroll in Part A and Part B
Apply online at SSA.gov, by calling Social Security at 1-800-772-1213, or in person at your local Social Security office. Apply during the first 3 months of your IEP for the earliest possible coverage start date.
Part A is free for most people (if you have 40+ work quarters). Part B costs $185.00/month in 2025 for most beneficiaries.
Step 5: Original Medicare or Medicare Advantage?
This is the most consequential coverage decision you will make. Compare plan options at Medicare.gov/plan-compare.
- Original Medicare: Access to any provider nationwide who accepts Medicare; no referrals; flexibility; no network. Continue to Steps 6 and 7.
- Medicare Advantage: All-in-one plan through a private insurer; often includes dental/vision/hearing; may have $0 premium; has provider networks and may require referrals. Skip to Step 8.
Step 6 (Original Medicare): Shop Medigap During Your Guaranteed Issue Window
For the 6 months after your Part B effective date, you have guaranteed issue rights for any Medigap plan — insurers cannot reject you or charge more based on pre-existing conditions. This window never comes back. If you want Medigap coverage, enroll now.
After this window closes, Medigap insurers can use medical underwriting to deny coverage or charge higher premiums. Most people who want Medigap and miss this window are locked out of affordable coverage.
Step 7 (Original Medicare): Choose a Part D Drug Plan
Original Medicare does not cover most prescription drugs. Enroll in a standalone Part D plan during your IEP. If you delay Part D without other creditable drug coverage, you face a permanent late enrollment penalty of 1% per month for every month you went without coverage.
Compare Part D plans at Medicare.gov/plan-compare by entering your medications to find the plan with the lowest total annual cost.
Step 8 (Medicare Advantage): Part D is Usually Included
Most Medicare Advantage plans are MA-PD plans that include Part D drug coverage. Verify that your chosen MA plan includes drug coverage, and review the formulary for your specific medications before enrolling.
Auto-Enrollment: What Happens If You're Already Getting Social Security
If you are receiving Social Security retirement or disability benefits before you turn 65, you do not need to do anything to enroll in Medicare — it happens automatically.
- You will be enrolled in both Medicare Part A and Part B automatically
- Your Medicare card will arrive in the mail approximately 3 months before your 65th birthday
- Your coverage begins on the first day of the month you turn 65
Even if auto-enrolled, you have the right to opt out of Part B if you have other qualifying coverage (such as employer GHP coverage from a current employer with 20+ employees). To opt out, return the card and follow the instructions included, or contact Social Security before your Part B effective date.
If you receive Social Security Disability Insurance (SSDI), you are generally auto-enrolled in Medicare after 24 months of receiving SSDI benefits — regardless of your age.
Part A: Almost Always Enroll at 65
For most people, enrolling in Medicare Part A at age 65 is a straightforward decision. Part A (hospital insurance) is premium-free if you or your spouse have at least 40 quarters (10 years) of Medicare-covered employment — which covers the large majority of people turning 65.
There is generally no downside to enrolling in Part A at 65, even if you have employer coverage. The main exception:
- If you are still working, covered by an employer health plan, and contributing to a Health Savings Account (HSA) — enrolling in Part A disqualifies you from making further HSA contributions. If maximizing HSA contributions is a priority, you may wish to delay Part A (and Part B) until you stop contributing to the HSA. Once enrolled in Part A, retroactive coverage goes back up to 6 months, so stop contributing 6 months before you plan to enroll.
The Medigap Guaranteed Issue Window: Do Not Miss It
One of the most consequential and irreversible Medicare decisions you face at 65 is whether to purchase a Medigap (Medicare Supplement) plan — and if so, you must act during your guaranteed issue window.
For the 6 months after your Part B effective date, federal law gives you guaranteed issue rights for any Medigap plan sold in your state. During this window:
- No insurer can deny you a Medigap plan based on health history or pre-existing conditions
- No insurer can charge you a higher premium because of your health status
- You can choose any standardized Medigap plan (A, B, C, D, F, G, K, L, M, N) available in your state
Once this window closes, Medigap insurers in most states are free to use medical underwriting: they can decline to sell you a policy, or they can charge substantially higher premiums based on your health conditions. People with diabetes, heart disease, cancer history, or many other conditions often find Medigap unaffordable or unavailable outside of their initial enrollment window.
This Window Never Comes Back
Unlike the Annual Enrollment Period for Medicare Advantage or Part D, the Medigap guaranteed issue open enrollment window is a one-time opportunity. If you decide you want Medigap later — after your health has changed — you may not be able to get it at a standard rate, or at all. If you want Medigap, the time to enroll is during the 6 months after your Part B effective date.
The most popular Medigap plans in 2025 are Plan G (covers everything except the Part B deductible) and Plan N (covers most cost-sharing with small copays for office visits). Compare Plan G vs Plan N here.
Medicare Advantage: Enrollment Timing and the Trial Right
If you choose Medicare Advantage during your IEP and later change your mind, you are not permanently locked in — but you do have a limited window to switch back. During the first 12 months of MA enrollment, you have a one-time Trial Right that allows you to switch back to Original Medicare and enroll in any Medigap plan with guaranteed issue rights.
Outside of this trial period, switching from Medicare Advantage back to Original Medicare requires waiting for the Annual Enrollment Period (October 15 through December 7 each year) or the Medicare Advantage Open Enrollment Period (January 1 through March 31). After the trial right period expires, Medigap guaranteed issue rights do not apply and underwriting can be used.
If you are not sure whether MA or Original Medicare is right for you, the safest sequence is: enroll in Original Medicare during IEP, enroll in Medigap during the guaranteed issue window, and then consider switching to MA if you decide you prefer it — you can always switch to MA during AEP.
2025 Medicare Costs at a Glance
| Item | What You Pay (2025) |
|---|---|
| Part A premium | $0 (if 40+ work quarters); $284–$518/month if fewer quarters |
| Part A deductible (per benefit period) | $1,676 |
| Part A coinsurance (days 61–90) | $419/day |
| Part B premium | $185.00/month (standard; higher with IRMAA) |
| Part B deductible (annual) | $257 |
| Part B coinsurance | 20% of Medicare-approved amount (after deductible) |
| Medicare Advantage premium | Varies — $0 to $200+/month depending on plan and location |
| Medigap Plan G premium | $100–$300+/month (varies by age, location, and insurer) |
| Part D premium | Varies — $0 to $200+/month depending on plan |
| Part D out-of-pocket cap (2025) | $2,000 (new in 2025 under the Inflation Reduction Act) |
Note: Higher-income beneficiaries pay more for Part B and Part D through Income-Related Monthly Adjustment Amounts (IRMAA), based on income reported to the IRS two years prior. See full 2025 Medicare cost details.
Turning 65 Medicare Checklist
Use this checklist to make sure you take every necessary step — in order — as you approach and pass your 65th birthday.
- Determine if you will be auto-enrolled. If you are already receiving Social Security benefits, you will be automatically enrolled. Verify your Medicare card arrives approximately 3 months before your 65th birthday. If it does not arrive, contact Social Security.
- Decide whether to enroll at 65 or delay. If you are working and covered by an employer GHP at a company with 20 or more employees, you may delay Part B without penalty. All other situations — COBRA, ACA Marketplace, retiree insurance — do not qualify for a delay. Enroll during your IEP.
- Apply for Part A and Part B. Apply online at SSA.gov, by phone at 1-800-772-1213, or in person at your local Social Security office. Apply during the first 3 months of your IEP for coverage to start the month you turn 65.
- Choose: Original Medicare or Medicare Advantage. Compare plans at Medicare.gov/plan-compare. Consider your doctors, medications, preferred hospitals, and travel patterns. Original Medicare offers the most flexibility; Medicare Advantage may offer lower costs if you stay in-network.
- If Original Medicare: shop Medigap plans during your guaranteed issue window. The 6-month window after your Part B effective date is your best — and potentially only — chance to get guaranteed issue Medigap coverage. Compare Plan G and Plan N from multiple insurers.
- If Original Medicare: enroll in a Part D plan. Even if you take few or no medications currently, enrolling in a low-premium Part D plan during IEP protects you from the late enrollment penalty. Compare plans at Medicare.gov/plan-compare using your current drug list.
- Notify your current insurance carrier. If Medicare is becoming your primary insurance, notify your current insurer so they can update their records and coordinate claims correctly. This is especially important if you have an employer plan that will become secondary.
- Check if you qualify for Extra Help (Low Income Subsidy). If your income is below approximately 150% of the Federal Poverty Level, you may qualify for Extra Help, which reduces Part D premiums, deductibles, and copays to near $0. Apply through Social Security (SSA.gov) or your state Medicaid agency.
- Check if you qualify for a Medicare Savings Program (MSP). Medicare Savings Programs are state-run programs that help pay Medicare premiums, deductibles, and cost-sharing for people with limited income and resources. MSPs can eliminate your Part B premium entirely. Apply through your state Medicaid agency.
Extra Help and Low Income Subsidy (LIS)
If your income and resources are limited, you may qualify for the Extra Help program — also called the Low Income Subsidy (LIS) — which dramatically reduces Part D costs:
- Part D premiums reduced or eliminated
- Part D deductible reduced or eliminated
- Drug copays reduced to a few dollars per prescription
- No coverage gap (the Part D "donut hole" does not apply)
Eligibility is based on income (generally below approximately 150% of the Federal Poverty Level) and limited resources. Apply at any time through the Social Security Administration online, by phone, or at a local Social Security office. You can also apply through your state Medicaid agency. There is no deadline — you can apply any time you become eligible.
People who qualify for Medicaid, Medicare Savings Programs, or Supplemental Security Income (SSI) are generally automatically eligible for Extra Help.
Frequently Asked Questions
The answer depends on whether you have qualifying employer coverage through your own active employment.
If you are not working or not covered by an employer GHP from a current employer with 20+ employees: Enroll during your Initial Enrollment Period — ideally in the first 3 months (before your birthday month) so coverage begins the month you turn 65. Missing your IEP without a qualifying reason results in a permanent 10%-per-year late enrollment penalty for Part B and gaps in coverage.
If you are actively working and covered by an employer GHP at a large employer (20+ employees): You can delay Part B without penalty. Enroll in Part A at 65 (it is free and there is generally no downside, unless you are contributing to an HSA). When you eventually leave that employer coverage, you will receive an 8-month Special Enrollment Period to sign up for Part B penalty-free.
If you are already receiving Social Security: You are automatically enrolled in Part A and Part B. Your Medicare card arrives approximately 3 months before your 65th birthday. Verify it arrives, then use the coverage start date to plan your Medigap and Part D enrollment.
The safest general rule: enroll during the first 3 months of your IEP unless you have confirmed qualifying employer GHP coverage that entitles you to delay.
The most urgent priority when you are newly enrolled in Medicare Part A and Part B is to make your coverage decisions within the windows that only open once.
First, decide between Original Medicare and Medicare Advantage. This is a foundational choice that shapes all other decisions. If you choose Original Medicare, you immediately enter your 6-month Medigap guaranteed issue window — the period during which you can buy any Medigap plan without medical underwriting. This window starts on your Part B effective date and lasts exactly 6 months. It does not repeat.
If you want Medigap (and most people who choose Original Medicare benefit from having it), shop and enroll in a plan as soon as your Part B is active. Compare Plan G and Plan N from multiple insurers in your state, as premiums for the same standardized plan vary significantly between companies.
Next, enroll in a Part D prescription drug plan during your IEP to avoid the late enrollment penalty and ensure drug coverage is in place.
After completing those steps, check whether you qualify for Extra Help (for Part D) or a Medicare Savings Program (which can eliminate the Part B premium). Apply through Social Security or your state Medicaid agency if you think you may be eligible.
Yes — you can enroll in Medicare while you are still working. Whether you should enroll, and for which parts, depends on your employer's size and the quality of your employer coverage.
Working at an employer with 20 or more employees: Your employer health plan is primary, Medicare is secondary. In this case, enrolling in Part B while working means paying $185/month for coverage that only pays after your employer plan — which may offer limited additional value. Most people in this situation enroll in Part A (free) and delay Part B until they retire or lose employer coverage, then use the 8-month Special Enrollment Period to sign up for Part B without penalty.
Working at an employer with fewer than 20 employees: Medicare is primary in this case. You should enroll in Part A and Part B during your IEP, even if you are still working. Failing to do so can leave your employer plan as primary payer on claims that Medicare should be handling first, which can create billing problems and coverage gaps.
One important exception: If you are contributing to a Health Savings Account (HSA), enrolling in Part A or Part B disqualifies you from making further HSA contributions. If HSA contributions are a priority, you may wish to delay Medicare enrollment — but be sure to time enrollment carefully before your employer coverage ends to avoid the late enrollment penalty.
Ready to Navigate Medicare at 65?
Understanding your enrollment windows and coverage options now prevents costly mistakes that can follow you for life. Explore the detailed guides below.
Medicare Enrollment Guide Medicare Eligibility Medigap Supplement Plans 2025 Medicare Costs