How to enroll in Medicare

Part A covers hospitalisation — inpatient stays, skilled nursing care, home health and hospice. Most people pay no premium for it because they or a spouse paid Medicare taxes while working.

Part B is medical insurance: doctors, outpatient care, diagnostics and preventive services. It has a monthly premium that nearly everyone pays.

Part C, Medicare Advantage, is a private insurance option that bundles hospital and medical cover into one plan, usually with prescriptions included and sometimes extras such as dental or vision. You are still in Medicare — you are receiving it through a private insurer under contract.

Part D covers prescription medications and is sold by private insurers.

Those parts assemble two ways. Original Medicare is Part A plus Part B, to which most people add a standalone Part D drug plan and often a Medigap supplement policy to cover the gaps. Medicare Advantage is the alternative: one private plan covering everything, typically with a provider network.

The trade-off is broadly access versus predictability. Original Medicare accepts almost any provider nationally but leaves cost-sharing you cover yourself or through Medigap. Medicare Advantage usually caps annual out-of-pocket spending and may cost less monthly, but restricts you to a network and may require referrals and prior authorisation.

If you are already receiving Social Security retirement benefits when you turn 65, you are enrolled in Parts A and B automatically. Your card arrives in the post, coverage starts on the first day of your birthday month, and there is nothing to do.

If you are not yet claiming Social Security — increasingly common, since many people delay to increase their monthly benefit — nothing happens automatically. You must sign up yourself, and this is where people get caught.

If you qualify through disability, Parts A and B start automatically after 24 months of Social Security disability benefits. ALS is the exception: coverage begins immediately on enrolment, with no waiting period.

Part D is never automatic. Whether you were auto-enrolled in A and B or signed up yourself, a drug plan is a separate active choice — and it carries its own late penalty.

You can check your status and enrol through the Social Security Administration, which administers Medicare enrolment even though Medicare itself is run by a different agency. That split surprises people looking for an enrolment form on Medicare.gov.

Your Initial Enrollment Period is seven months long: the three months before the month you turn 65, your birthday month itself, and the three months after. This is the cleanest window and the one to use.

Enrol in the first three months if you can. Coverage then starts at the beginning of your birthday month with no gap. Signing up during or after your birthday month can delay the start date, leaving you uninsured for weeks.

If you miss it entirely, the General Enrollment Period is the fallback, but it means waiting, a later coverage start, and probable penalties.

Special Enrollment Periods exist for people who delayed because they had qualifying coverage — most commonly a current employer's group plan. Used correctly, a Special Enrollment Period avoids the penalty altogether.

Medicare Advantage and Part D have their own annual windows for switching plans, separate from the enrolment periods above. Changing plan and enrolling for the first time are governed by different calendars.

The Part B late penalty is the one to take seriously, because it is permanent. It is added to your monthly premium and stays for as long as you have Part B — not for a year, not until you catch up, but indefinitely. It also scales with how long you delayed.

The Part D penalty works similarly. It applies if you go without creditable prescription coverage for a sustained period after becoming eligible, and it too attaches to your monthly premium permanently.

'Creditable coverage' is the phrase that matters. Drug coverage from an employer or union that is at least as good as Part D counts, and time under it does not trigger a penalty. Your plan administrator must tell you each year whether your coverage is creditable — keep those letters, because they are the evidence if a penalty is ever assessed.

Part A rarely carries a penalty, because most people qualify for it premium-free.

The compounding effect is what makes these penalties expensive. A modest monthly addition, paid for twenty or thirty years of retirement, is a substantial sum — which is why a decision that feels minor at 65 is worth an hour of attention.

Start with your doctors. If you have specialists you intend to keep, check directly whether they accept the specific Advantage plan you are considering — not whether they 'accept Medicare', which is a different question. Original Medicare is accepted by the large majority of providers nationally.

Then check your prescriptions. Every Part D and Advantage plan has a formulary listing which drugs it covers and at what tier, and the same medication can differ enormously in cost between plans. Medicare's plan comparison tool lets you enter your actual prescriptions and see total projected annual cost rather than headline premium.

Consider how much you travel. Original Medicare works anywhere in the country; Advantage networks are usually regional, which matters if you spend months elsewhere or split the year between two states.

If you are leaning towards Original Medicare, look at Medigap early. Supplement policies have their own enrolment window with guaranteed acceptance regardless of health, and outside it insurers can in many states refuse you or charge more based on medical history. This window is easy to miss and hard to reopen.

Compare on total expected annual cost — premiums, deductibles, copays and drug costs together — rather than the monthly premium alone. A low-premium plan with poor drug coverage frequently costs more overall.

Free, unbiased help exists. Every state runs a State Health Insurance Assistance Program offering one-to-one counselling at no charge, staffed by people with no commission and nothing to sell. It is consistently the most useful resource and the least known.

Premiums, deductibles and the income-related adjustment that raises Part B and D premiums for higher earners are all set annually. Figures are deliberately not quoted here so this page cannot go quietly out of date — check Medicare.gov for the current year.

If your income is limited, several programmes reduce or eliminate what you pay. Medicare Savings Programs can cover premiums and cost-sharing, and Extra Help reduces prescription costs substantially. Both are underclaimed, and both are worth applying for even if you are unsure you qualify.

Medicaid and Medicare are different programmes and you can hold both. People who do are described as dual eligible, and Medicaid then covers much of what Medicare does not.

The mistakes that cost most: assuming enrolment is automatic when you are not yet claiming Social Security; skipping Part D because you take no medications now, which starts the penalty clock; missing the Medigap window; and choosing an Advantage plan on premium alone without checking whether your doctors and drugs are covered.

Medicare does not cover most long-term custodial care, routine dental, vision or hearing under Original Medicare, or care outside the United States except in narrow circumstances. Some Advantage plans add dental and vision, which is a genuine point of difference.

Beware anyone who telephones you about Medicare. Medicare does not cold-call to sell plans or ask for your number, and enrolment season brings a reliable wave of fraud.