Turning 65 is a major milestone, and not just because it marks a new chapter in life. For millions of Americans, it means navigating one of the most important financial decisions they will ever face: choosing the right health insurance coverage through Medicare. Whether you are retiring, still working, or somewhere in between, understanding your options is critical to protecting both your health and your finances.
This guide walks you through the structure of Medicare, the deadlines that genuinely cannot be missed, the special rules for people still working at 65, and the situations — military retirees, federal employees, low-income beneficiaries — where the standard advice does not apply.
The Basics: What Is Medicare?
Medicare is the federal health insurance program primarily for people aged 65 and older, along with certain younger people with disabilities. It is divided into parts, each covering different services.
Medicare Part A: Hospital Insurance
Part A covers inpatient hospital stays, skilled nursing facility care, hospice care, and some home health services. Most people pay no premium for Part A if they or their spouse paid Medicare taxes for at least 10 years (40 quarters). Part A is not free to use, however: in 2026 it carries a deductible of $1,736 per benefit period — and because a benefit period resets after 60 days out of the hospital, you can owe that deductible more than once in a year.
Medicare Part B: Medical Insurance
Part B covers doctor visits, outpatient care, preventive services, and durable medical equipment. The standard Part B premium in 2026 is $202.90 per month, with higher-income beneficiaries paying more under the Income-Related Monthly Adjustment Amount (IRMAA). The 2026 Part B deductible is $283, after which Medicare generally pays 80% of approved charges and you pay 20% — with no cap, which is precisely the gap that Medigap and Medicare Advantage exist to address.
Medicare Part C: Medicare Advantage
Medicare Advantage plans are offered by private insurers approved by Medicare. They bundle Part A and Part B, usually include Part D drug coverage, and often add dental, vision, or hearing benefits, frequently at low or zero additional premium. In exchange, you typically accept a provider network and prior authorization requirements.
Medicare Part D: Prescription Drug Coverage
Part D is prescription drug coverage sold by private insurers, either as a standalone plan alongside Original Medicare or built into a Medicare Advantage plan. Part D has improved dramatically in recent years: in 2026, your out-of-pocket drug costs are capped at $2,100 for the year, and the Medicare Prescription Payment Plan lets you spread those costs in monthly installments rather than paying large sums at the pharmacy counter. For anyone taking expensive medications, this cap alone is a transformative protection.
The Decision: Original Medicare with Medigap, or Medicare Advantage
This is the biggest choice most people face at 65. Original Medicare plus a Medigap supplement plus a Part D plan gives you access to virtually any doctor or hospital that accepts Medicare nationwide, with most cost-sharing filled in by the supplement — at the price of a meaningful monthly Medigap premium. Medicare Advantage usually costs less per month and bundles extras, but limits your network, requires plan approval for some care, and exposes you to the plan out-of-pocket maximum in a bad health year. The right answer depends on your health, your doctors, how much you travel, and your tolerance for network restrictions versus premiums.
The Medigap Window: Six Months, Once in a Lifetime
If there is one deadline in all of Medicare that deserves a circle in red ink, it is this. Your Medigap open enrollment period lasts exactly six months, starting the month you are 65 or older and enrolled in Part B. During that window, insurers must sell you any Medigap policy they offer at standard rates, regardless of your health history. This guaranteed-issue right is one-time and does not repeat. Outside the window, in most states, Medigap insurers can decline you or charge more based on preexisting conditions.
The practical consequence: if you start with Medicare Advantage and develop a serious illness years later, you may find you cannot switch to Original Medicare plus Medigap, because no insurer will write you an affordable supplement. There are limited trial rights and a handful of states with year-round protections, but for most people the choice made at 65 is stickier than it appears. Decide as if it were permanent.
Still Working at 65? Read This Before Enrolling
More people than ever work past 65, and the rules here are where expensive mistakes happen. If you (or your spouse) are actively employed and covered by an employer group plan from an employer with 20 or more employees, that coverage pays primary and you can delay Part B — and Part D, if the drug coverage is creditable — without penalty. When the employment ends, you get an eight-month Special Enrollment Period to pick up Part B penalty-free.
Three traps inside this rule:
- Small employers are different. If the employer has fewer than 20 employees, Medicare pays primary at 65 even if you keep the group plan — and if you have not enrolled in Part B, you can be left with the group plan paying only secondary on bills Medicare was supposed to cover. Enroll in Part B.
- COBRA and retiree coverage do not count. Only coverage from active employment lets you delay Part B without penalty. People who ride COBRA past 65 and skip Part B routinely discover the error only when the penalty letter arrives.
- HSA contributions must stop. You cannot contribute to a Health Savings Account in any month you are enrolled in any part of Medicare, including premium-free Part A. And if you enroll in Medicare after 65, Part A is backdated up to six months. Plan ahead: stop HSA contributions at least six months before your Medicare enrollment takes effect, and prorate your final-year contribution, or you will face excess-contribution taxes. You can still spend existing HSA money — including on Medicare premiums — you just cannot add to it.
The Penalties for Enrolling Late
Medicare enforces its deadlines with lifetime penalties. Miss your Part B enrollment without qualifying employer coverage and your premium rises by 10% for each full 12-month period you went without it — added to the $202.90 standard premium, for life. The Part D penalty accrues faster than people expect: 1% of the national base premium for every month you lacked creditable drug coverage, also permanent. Going two years without creditable drug coverage means paying roughly a quarter extra on your Part D premium forever. Your Initial Enrollment Period spans seven months — the three months before your birthday month, the month itself, and the three months after. Enrolling in the early months gets coverage started the month you turn 65.
Special Situations Worth Knowing
TRICARE For Life: Part B Is Not Optional
Military retirees and eligible family members move to TRICARE For Life at 65, which acts as generous wraparound coverage to Medicare — but only if you enroll in Part B. Decline Part B and you lose TRICARE coverage almost entirely. The Part B premium is, in effect, the price of keeping TRICARE, and it is nearly always worth paying.
Federal Employees: FEHB Plus Medicare
Federal retirees can keep FEHB coverage for life alongside Medicare. Because FEHB continues as retiree coverage, there is no penalty pressure forcing a Part B decision while still employed past 65 — but in retirement, many federal annuitants find that pairing FEHB with Part B effectively eliminates most out-of-pocket costs, since many FEHB plans waive their own cost-sharing for members with Part B, and some rebate part of the Part B premium. Whether the added premium is worth it depends on your plan and health, but the combination is one of the strongest retiree arrangements in the country and deserves a careful look rather than a reflexive no.
Limited Income: Dual Eligibility, D-SNPs, and Extra Help
If your income and resources are modest, do not pay full freight. People who qualify for both Medicare and Medicaid — dual eligibles — can enroll in Dual Eligible Special Needs Plans (D-SNPs), Medicare Advantage plans built to coordinate the two programs, often with very low out-of-pocket costs and extra benefits. Even above Medicaid levels, Medicare Savings Programs run through your state can pay the Part B premium: QMB at or below 100% of the federal poverty level covers premiums and cost-sharing, while SLMB (up to 120%) and QI (up to 135%) pay the Part B premium. And the Part D Extra Help program, expanded in 2024, now provides its full subsidy to anyone up to 150% of the poverty level — covering most drug plan premiums and reducing copays to nominal amounts. These programs are persistently underenrolled; a single application through your state Medicaid office can be worth thousands of dollars a year.
Putting It Together
Three questions resolve most of the complexity. First, are you or your spouse still actively working with large-employer coverage? That determines whether you enroll now or later. Second, Original Medicare with Medigap or Medicare Advantage? Make that call during your six-month Medigap window as if it were permanent. Third, do any special rules apply to you — TRICARE, FEHB, HSA contributions, or limited income? Each has its own playbook. Get those three answers right, on time, and you will have made the decisions at 65 that protect both your health and your wallet for decades.