If you are turning 65 and already receive Social Security retirement benefits or Railroad Retirement Board benefits, you will get a welcome packet from Medicare about three months before your birthday. You do not have to apply for Medicare.

If you are younger than 65 and get Social Security Disability Insurance (SSDI) you will get Medicare automatically starting the 25^th month after your SSDI benefits start. People with ALS (amyotrophic lateral sclerosis, also called Lou Gehrig’s disease) also get Medicare automatically as soon as they start getting disability benefits.

People age 65 who do not get Social Security retirement benefits can sign up online for Medicare Parts A or B.

You can also sign up by calling Social Security at 1-800-772-1213. Social Security phone lines are open in most U.S. time zones Monday through Friday, 8 a.m. to 7 p.m., in English, Spanish, and other languages.

Or you can visit your local Social Security office in person.

There are three windows of time when you can first join Medicare. You need to pay attention to these and your situation, because not signing up on time can lead to late fees and gaps in health coverage.

1. The Initial Enrollment Period is a seven-month window around your 65^th birthday.
2. Special Enrollment Periods are available to people with special circumstances, such as working past age 65 and having employer insurance.
3. The General Enrollment Period is a time each year when people can sign up if they missed the first two periods.

Learn more about each enrollment period and their timing at Social Security’s website.

Note: There is special timing for people with End Stage Renal Disease (ESRD, or kidney failure).

If you or your spouse is actively working and have health insurance through your job, you may not need to sign up for Medicare right away. But this depends on the size of your company and whether your insurance requires you to take Medicare.

• Learn more at Medicare.gov.

You can have Medicare and other insurance, such as retiree coverage or TRICARE for Life. See how these work together in the official Medicare publication, Who Pays First?.

Need more help with enrollment decisions?

Contact your State Health Insurance Assistance Program (SHIP)

Not sure whether to contact Social Security or Medicare? Check out this handy fact sheet explaining who to contact when.

Original Medicare (sometimes called Traditional Medicare) has two parts: Part A and Part B. Part A is hospital insurance and mostly covers inpatient care. Part B covers outpatient care and services meant to keep you healthy, such as preventive care and some medical equipment.

Original Medicare can be used anywhere in the United States if the provider accepts Medicare. You do not need to change coverage if you move between states or spend part of the year in a different area from your home.

Original Medicare covers many services, but it does not cover most prescription drugs or routine vision, hearing, or dental care. Learn what other services and items Original Medicare does not cover.

Medicare Part C is known as Medicare Advantage. Medicare Part D is a separate prescription drug plan. Both Medicare Advantage and Part D plans are offered by private companies. You must sign up for Medicare Part A and/or Part B before you can join these plans.

Medicare Advantage bundles Original Medicare (Parts A and B) but also usually includes prescription drug coverage and other benefits, such as vision and dental care. Part D plans are standalone and only cover prescription drugs; each plan has a different formulary (approved drug list) and chooses which drugs it covers, and at what price.

Not everyone needs or can join a Medicare Advantage or Part D plan. Enrollment depends on your needs, whether you get Medicare because of age or disability, and if you have other health insurance. Learn more about health and drug plans at Medicare.gov.

Medigaps are health insurance policies that work with Original Medicare. They are sometimes called Medicare supplemental plans and are sold by private insurance companies.

A Medigap policy pays part or all of certain remaining costs after Original Medicare pays first. Most people (except if you live in Massachusetts, Minnesota, or Wisconsin) have 10 different Medigap policies to choose from: A, B, C, D, F, G, K, L, M, and N. Each policy with the same letter offers the same benefits.

Medigaps only work with Original Medicare. You cannot have both a Medicare Advantage plan and Medigap.

There are special rules about when you can buy a Medigap policy, and limitations on switching policies. See Medicare.gov for more information.

If you do not sign up for Medicare at specific times, and don’t have other health coverage as good as Medicare (such as employer insurance), you may have to pay a late enrollment penalty. This penalty is a specific amount added to the different parts of Medicare and the amount depends on how long you went without coverage. It is not a one-time fee. You may have a penalty for as long as you have Medicare.

Learn more about how the penalty is calculated and how to avoid it.

Medicare Advantage and Part D plans can only change their plan premiums and deductibles once a year for the next calendar year. But sometimes your costs during the year will change when you meet your deductible or because of changes in drug pricing.

There are two benefits that help people with limited income to afford Medicare:

• Medicare Savings Programs are a type of Medicaid that help people pay the Medicare Part B premium (and sometimes other costs). You may hear these called by their acronyms QMB, SLMB or QI.
• Extra Help (also called the Part D Low-Income Subsidy or LIS) helps lower the cost of prescriptions and Part D plans.

Your local SHIP can help you to apply for these two programs.