Medicare Guide

How to Enroll in Medicare

Medicare enrollment is not one button. Some people are enrolled automatically. Some need to apply through Social Security. Railroad workers may go through the Railroad Retirement Board. And after Parts A and B are handled, Medicare Advantage, Part D, and Medicare Supplement decisions follow their own process. This guide walks through the order so you do not miss the practical details.

Reviewed by Jeremy Weiser, Licensed Insurance Agent since 2007 · Published May 15, 2026 · Last updated August 14, 2026

Quick answer

Most people enroll in Medicare Part A and Part B through Social Security, but some people are enrolled automatically.

If you already receive Social Security or Railroad Retirement benefits before Medicare starts, you may get Part A and Part B automatically. If not, you usually sign up through Social Security. After that, you can compare whether to use Original Medicare with optional add-ons or enroll in a Medicare Advantage plan.

Key takeaways

Part A and Part B enrollment usually goes through Social Security, not a private insurance company.
Automatic enrollment depends on whether you are already receiving Social Security or Railroad Retirement benefits before Medicare starts.
People with current employer coverage should check Part B timing before signing up or delaying.
Medicare Advantage, Part D, and Medicare Supplement enrollment are separate from getting Original Medicare.
The best enrollment plan starts before the coverage date you want, not after your old coverage ends.

Enrollment numbers

The timing details to keep on your radar

These are the common enrollment numbers, but your own timing can change if you already receive benefits, work past 65, have ESRD, live in Puerto Rico, or need a plan to start on a specific date.

Initial window

7 monthsMost people turning 65 can first sign up during the 3 months before, the month of, and the 3 months after their birthday month.

Automatic enrollment

4 monthsMedicare.gov says many people are automatic at 65 if Social Security or RRB benefits started at least 4 months before turning 65.

Welcome package

About 2 weeksMedicare says a welcome package usually arrives about 2 weeks after signing up for Medicare or Social Security benefits.

Working SEP

8 monthsSome people with qualifying current employer coverage can use an 8-month Part B Special Enrollment Period after work or coverage ends.

Start with Parts A and B

The first enrollment question is usually Original Medicare: Part A for hospital coverage and Part B for medical coverage. Most people handle Part A and Part B through Social Security. You may sign up online, call Social Security, or work with a local Social Security office. If you or your spouse worked for a railroad, the Railroad Retirement Board may be the right contact instead.

Know whether you are automatic or need to apply

Some people get Medicare automatically. For example, Medicare.gov says people who start receiving Social Security or Railroad Retirement benefits at least 4 months before turning 65 are generally enrolled automatically in Part A and Part B, with a welcome package mailed before coverage starts. If you are not already receiving those benefits, do not wait for a card that may never come. You usually need to sign up.

Do not enroll blindly if you are still working

If you or your spouse has current employer group coverage, Part B timing deserves a careful look. Some people can delay Part B without a penalty. Others cannot. COBRA, retiree coverage, Marketplace coverage, VA care, and small-employer coverage can all change the answer. Before applying, ask the employer benefits administrator how the plan coordinates with Medicare and whether Medicare should pay first.

Gather the details before you start the application

Social Security asks for basic personal information and health insurance details, including dates for current group health plans and group health plans after age 65. If you are signing up for Part B only because you already have Part A, you may also need your Medicare number. Having those dates ready makes the application cleaner and helps avoid a wrong coverage start date.

Choose the coverage start date on purpose

Enrollment is not only about getting approved. It is about making Medicare start when you need it. People retiring from employer coverage often want Part B to begin the month after employer coverage ends. People who are turning 65 may want coverage to start as soon as they are eligible. People with ESRD or disability rules may have a different timeline. The coverage date should match the real-life transition.

Then compare the plan path

After Parts A and B are settled, the next decision is how you want your Medicare coverage arranged. One path is Original Medicare, often with a Part D drug plan and possibly a Medicare Supplement policy. The other path is Medicare Advantage, where a private plan provides your Medicare benefits and may include drug coverage. That choice should be based on doctors, prescriptions, budget, travel, county availability, and how much flexibility you want.

Watch for the mail, then verify the card

After you sign up, Medicare says the welcome package usually arrives in about 2 weeks. Review the card when it comes. Check whether it lists Part A, Part B, or both, and confirm the effective dates. If the dates do not match what you expected, fix it before you enroll in a plan or cancel other coverage.

Use help for the comparison, not for shortcuts around the official process

A Medicare advisor can help you compare coverage paths, drug plans, doctors, plan networks, and next steps. But Part A and Part B enrollment itself generally belongs with Social Security or the Railroad Retirement Board. That distinction matters. The safest process is official enrollment first, plan comparison second, and then a final check that the dates line up.

Coverage paths

The two big Medicare paths people usually compare

The right answer is not the same for everyone. The better question is which path fits the way you use care.

Turning 65

If you are not already receiving Social Security or Railroad Retirement benefits, plan to apply during your Initial Enrollment Period. Decide whether you need both Part A and Part B, then compare the plan path before coverage starts.

When to Enroll in Medicare Who Is Eligible for Medicare?Medicare Part B

Retiring after 65

If employer coverage is ending, start early enough to confirm the Part B start date, employer forms, drug coverage, and whether a Special Enrollment Period applies.

Still Working at 65?Special Enrollment Periods Part D Enrollment Periods

Choosing coverage after Parts A and B

Once Original Medicare timing is set, compare whether Medicare Advantage or Original Medicare with add-ons fits your doctors, prescriptions, budget, and travel habits.

Medicare Advantage vs Medicare Supplement Medicare Part D Medicare Supplement Plans

Go deeper

Related Medicare guides

Use this page as your Medicare starting point, then jump into the specific topic that matches your situation.

Common questions

Questions people usually ask next

These answers are a starting point. Medicare details can change based on timing, other coverage, and where you live.

Do I sign up for Medicare through The Medicare Store?

No. Part A and Part B enrollment usually goes through Social Security, or the Railroad Retirement Board for people with railroad benefits. The Medicare Store can help you understand timing and compare coverage options after the official enrollment step.

Will Medicare enroll me automatically when I turn 65?

Maybe. If you are already receiving Social Security or Railroad Retirement benefits before Medicare starts, enrollment may be automatic. If you are not receiving those benefits, you usually need to sign up.

Can I enroll in Medicare online?

Yes, many people can enroll online through Social Security. Some situations may require calling Social Security, contacting a local office, or using the Railroad Retirement Board.

Should I enroll in Part B if I still have employer coverage?

It depends on whether the coverage is based on current employment and how it coordinates with Medicare. Check before enrolling or delaying, especially if COBRA, retiree coverage, Marketplace coverage, VA care, TRICARE, or an HSA is involved.

Is signing up for Medicare the same as choosing a Medicare Advantage or Part D plan?

No. Getting Part A and Part B is the Original Medicare enrollment step. Medicare Advantage, Part D, and Medicare Supplement choices are separate decisions with their own rules and timing.

Official references

Sources checked for this guide

These guides are written in plain English, but the 2026 cost figures and coverage rules should stay tied to official Medicare and CMS source material.

Medicare.gov: How do I sign up for Medicare?SSA: Sign up for Medicare Medicare.gov: When can I sign up for Medicare?Medicare.gov: Working past 65 CMS: Original Medicare eligibility and enrollment Medicare.gov: Joining a health or drug plan Medicare.gov: Buying a Medigap policy RRB: Medicare

About the reviewer

Jeremy Weiser · Licensed Insurance Agent since 2007 · Nevada license #566932

Jeremy Weiser is the CEO and a principal of The Medicare Store and has been a licensed insurance agent since 2007 (Nevada license #566932). With nearly two decades in health and Medicare insurance, he leads the standards behind the guidance The Medicare Store gives every client.

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