Four parts, one decision
Medicare is the federal health insurance program for people 65 and older and for certain younger people with disabilities. The alphabet is less complicated than it looks.
Part A is hospital insurance: inpatient stays, skilled nursing care after a hospital stay, hospice. Most people pay no Part A premium because they or a spouse paid Medicare taxes long enough while working.
Part B is medical insurance: doctor visits, outpatient care, preventive services, durable medical equipment. It carries a monthly premium. For 2026, CMS set the standard Part B premium at $202.90 per month and the annual deductible at $283. Higher incomes pay more on a sliding scale.
Part D is prescription drug coverage, sold by private insurers under federal rules.
Part C, called Medicare Advantage, is not a separate benefit. It is a different way to get the others: a private plan that bundles A, B, and usually D, often with extras like dental or vision, in exchange for provider networks and plan-managed care.
So the real decision is structural. Original Medicare (A plus B, plus a Part D plan, often plus a Medigap supplement to cap your out-of-pocket exposure) buys you nearly any doctor who accepts Medicare. Medicare Advantage buys convenience and sometimes lower premiums, paid for with networks and prior authorization rules. Neither is automatically right. Medicare.gov’s plan finder compares the actual plans available where you live, which is the only comparison that matters.
The enrollment windows, because they bite
Medicare enrollment runs on fixed windows, and missing them has permanent prices.
Your initial enrollment period spans seven months: the three months before the month you turn 65, your birthday month, and the three months after. People already receiving Social Security benefits are typically enrolled in A and B automatically. Everyone else applies, and the front door is ssa.gov, since the Social Security Administration handles Medicare enrollment.
Still working at 65 with employer coverage? You may be able to delay Part B without penalty under special enrollment rules tied to active employment. The rules are specific, and the safe move is confirming your exact situation through medicare.gov or Social Security before you decide anything. Guessing wrong here costs money forever.
That is not an exaggeration. The Part B late enrollment penalty adds a surcharge for each year you were eligible but not enrolled, and it generally lasts as long as you have Part B. Part D has its own late penalty. The system forgives very little, which is why the seven-month window deserves a spot on your actual calendar.
After you are in, the annual rhythm is gentler. Medicare open enrollment runs October 15 to December 7 every year. You can switch between Original Medicare and Medicare Advantage, change Advantage plans, or change drug plans, effective January 1.
What Medicare does not cover
Original Medicare does not cap your annual out-of-pocket spending the way marketplace plans do, which is the gap Medigap policies exist to fill. It generally does not cover long-term custodial care, most dental, vision, and hearing, or care outside the United States. Anyone telling you Medicare makes all health spending disappear at 65 has not read the program.
One timing detail inside the gaps: Medigap has its own best window. Your six-month Medigap open enrollment starts when you are 65 or older and enrolled in Part B, and during it insurers generally cannot decline you or surcharge you for health history. Miss it, and in most states they can. If Original Medicare is your path, decide on Medigap inside that window, not after.
Budget honestly: premiums for B and D, any Medigap or Advantage premium, and the deductibles and cost-sharing your chosen path carries. The structure of deductibles and coinsurance works the same way here as everywhere else in health insurance. Our deductibles explainer covers the vocabulary.
Where to do everything
Use official sources, full stop. Enrollment runs through ssa.gov. Plan comparison, coverage rules, and costs live at medicare.gov. Every October, re-shop your Part D or Advantage plan during open enrollment. Plans change their drug lists and pricing every year, and the plan that fit you in 2024 may quietly fit you badly in 2026.
That annual re-shopping habit is the most valuable money skill in retirement, and it transfers. The car insurance bill arriving on autopilot responds to exactly the same treatment: quotes from competing carriers, once a year, twenty minutes. Compare auto insurance rates alongside your Medicare review, and make both renewals earn their place in a fixed-income budget.