You can start Medicare at 65, but you need to sign up during a specific window or face penalties

Medicare enrollment happens in three windows: before you turn 65, when you turn 65, and after. The timing matters because late enrollment penalties are permanent — they add to your monthly premium for as long as you have Medicare. You do not have to wait until your birthday month; you can start the process three months before you turn 65.

Most people sign up through Medicare.gov, by phone, or in person at a Social Security office. The process itself takes about 10 minutes online or 15 to 20 minutes on the phone. You will need your Social Security number, birth date, and citizenship or immigration status. If you are still working and have health insurance through your job, the rules are different — read the section below on employer coverage before you proceed.

Key Takeaways

  • You can start the enrollment process three months before you turn 65, and you should do so to avoid permanent penalties on your monthly bill.
  • If you are still working and covered by your employer's health plan, you may be able to delay Part B enrollment without penalty — but you must tell Medicare this when you sign up.
  • Medicare has two main parts: Part A (hospital) is usually free if you paid payroll taxes for 10 years, and Part B (doctor visits) costs a monthly premium based on your income.
  • You choose between Original Medicare (Parts A and B) and Medicare Advantage (Part C), and you can add prescription drug coverage (Part D) to either one.
  • Your first chance to make changes without penalty is during the Initial Enrollment Period, which runs from three months before your 65th birthday through three months after.

The three enrollment windows and what each one means

Your Initial Enrollment Period is seven months long: it starts three months before the month you turn 65 and ends three months after. During this window, you can sign up for any part of Medicare without waiting periods or penalties. This is the only time you get this protection, so it is the best time to enroll even if you do not plan to use Medicare right away.

If you miss the Initial Enrollment Period, you enter the General Enrollment Period, which runs January 1 through March 31 each year. You can sign up then, but your coverage does not start until July 1, and you will owe a permanent 10 percent penalty on Part B premiums for each full year you delayed. The penalty stays on your bill forever.

If you are still working and covered by your employer's health plan, you may may have access to for a Special Enrollment Period that lets you delay Part B without penalty. This applies only if your employer has 20 or more employees and you are actually covered by their plan. You must tell Medicare you are using this exception when you sign up for Part A; if you do not, you will be charged the late penalty even though you may have access to for the exception.

Part A versus Part B: what each one covers and what it costs

Part A covers hospital stays, skilled nursing facility care, hospice, and home health services. Most people pay nothing for Part A if they or their spouse paid Medicare payroll taxes (the 1.45 percent deducted from paychecks) for at least 10 years. If you do not meet this requirement, you can buy Part A, but the monthly premium varies based on how many years you paid the tax.

Part B covers doctor visits, outpatient care, lab tests, and some preventive services. Part B has a monthly premium that changes each year; it also depends on your income from two years ago. If your income was below a certain threshold, you pay the standard premium. If it was higher, you pay an income-related surcharge on top of the standard amount. You will also owe a 10 percent penalty for each year you delayed Part B, unless you had employer coverage or another may have access to exception.

You must have Part A to get Part B, but you do not have to take both at the same time if you have employer coverage. Part A and Part B together are called Original Medicare. If you choose Original Medicare, you can add Part D (prescription drug coverage) and Medigap (supplemental insurance) separately.

Original Medicare versus Medicare Advantage: how to choose

Original Medicare is the traditional program run by the federal government. You go to any doctor or hospital that accepts Medicare. You pay a deductible and coinsurance (a percentage of the cost) for each service. There is no yearly cap on what you pay out of pocket, so costs can be high if you have a serious illness. You can add Medigap to cover some of these costs, and you can add Part D for prescriptions.

Medicare Advantage (Part C) is an alternative run by private insurance companies. It includes Part A, Part B, and usually Part D all in one plan. You typically pay lower monthly premiums and have a yearly cap on out-of-pocket costs. The trade-off is that you usually have to use doctors and hospitals in the plan's network, and you may need approval before certain services. Medicare Advantage plans change every year, so you need to check your plan's coverage and costs annually.

You choose between Original Medicare and Medicare Advantage during your Initial Enrollment Period. You can switch between them during the Annual Enrollment Period (October 15 through December 7 each year), but if you drop Medicare Advantage and go back to Original Medicare, you can only add Medigap during certain windows — missing these windows can leave you with gaps in coverage.

How to sign up: online, by phone, or in person

The easiest way to sign up is online at Medicare.gov. You create an account, answer questions about your coverage history, and choose your plan. The site shows you what each plan costs based on your zip code and health needs. You can compare Original Medicare with Medicare Advantage plans side by side. The whole process takes about 10 minutes, and you get a confirmation number right away.

You can also call Social Security at 1-800-772-1213 (TTY 1-800-325-0778) to sign up by phone. Have your Social Security number, birth date, and current health insurance information ready. The call usually takes 15 to 20 minutes. Social Security will mail you a confirmation letter within two weeks.

If you prefer to sign up in person, visit your local Social Security office. You can find the nearest one on Social Security.gov. Bring your Social Security card, birth certificate, and proof of citizenship or immigration status. You do not need an appointment, but wait times vary by location and time of day.

What happens after you sign up: when coverage starts and what to expect

If you sign up during your Initial Enrollment Period, your coverage starts on the first day of the month you turn 65 (or the first day of the month after you sign up, whichever is later). You will receive a Medicare card in the mail about two weeks before your coverage starts. The card has your Medicare number on it; bring it to all doctor visits.

You will also receive a document called the "Medicare & You Handbook" in the mail. It explains your coverage, your rights, and how to file a complaint if something goes wrong. Keep it handy — it answers many questions about how Medicare works.

If you chose Original Medicare, you can start using it right away. If you chose Medicare Advantage, your plan will send you information about how to access care, which doctors are in the network, and how to request prior authorization if you need it. If you added Part D, your pharmacy will have your coverage information on file.

Special situations: employer coverage, disability, and end-stage renal disease

If you are still working and covered by your employer's health plan, you can delay Part B without penalty — but only if your employer has 20 or more employees. When you do sign up for Part B, you must tell Medicare that you had employer coverage. You do this by providing a letter from your employer or your health plan stating that you were covered. Without this letter, Medicare will charge you the late penalty even though you may have access to for the exception.

If you are under 65 and receive Social Security Disability Insurance (SSDI), you become may be able to access for Medicare automatically after you have been on SSDI for 24 months. You do not have to sign up; Medicare starts on the 25th month of your disability. You will receive a Medicare card in the mail.

If you have end-stage renal disease (ESRD) or ALS (amyotrophic lateral sclerosis), you may be may be able to access for Medicare before 65. Contact Social Security or Medicare to find out whether you may have access to and how to enroll.

Frequently Asked Questions

What happens if I miss my Initial Enrollment Period?

You can still sign up during the General Enrollment Period (January 1 through March 31), but your coverage will not start until July 1, and you will owe a permanent 10 percent penalty on your Part B premium for each full year you delayed. The penalty stays on your bill for life, so it is worth signing up as soon as possible even if you miss the Initial Enrollment Period.

Do I have to take Medicare at 65 if I am still working?

If you have employer coverage through your job, you can delay Part B without penalty. You must have Part A, but you can delay Part B as long as you are actively working and covered by your employer's plan. When you leave your job or lose coverage, you have eight months to sign up for Part B without penalty.

Can I change my mind after I sign up?

Yes, but only during certain windows. You can change your plan during the Annual Enrollment Period (October 15 through December 7). If you just signed up and are still in your Initial Enrollment Period, you can make changes anytime. After that, changes are limited to specific situations like moving out of your plan's service area or losing employer coverage.

How much will Medicare cost me?

Part A is usually free. Part B costs a monthly premium that varies by year and income; in recent years it has ranged from around $165 to over $500 per month depending on your income. Medicare Advantage plans vary widely in cost. You will also have deductibles and coinsurance for services. The exact amount depends on which plan you choose and your income.

What if I do not have 10 years of work history for Part A?

You can buy Part A even if you do not may have access to for free Part A. The monthly premium depends on how many years you paid Medicare taxes. If you paid for at least five years, the premium is lower than if you paid for fewer than five years. You can find the exact amount on Medicare.gov or by calling Social Security.