While Medicare is likely a term you’ve heard, you might not exactly know what it is. And with that, you might not be sure if you are eligible and or when and how to enroll.

In simple terms, Medicare is a government health care program for people 65 and over.

What people don’t know is that millions of people under the age of 65 may also be eligible for Medicare but aren’t receiving benefits. To discover if you are eligible, take this quick quiz before reading on.

How do you enroll?

Conveniently, if you’ve been receiving Social Security benefits when you turn 65, you will be automatically enrolled in certain aspects of Medicare. You’ll be auto enrolled in Medicare Part A, which covers hospital costs, and Part B, which covers doctor visits. There is an option to enroll in Medicare Part D, which would cover prescription drug costs, but you will need to enroll yourself as it is not automatic.

Not receiving Social Security benefits? No sweat. Simply sign up through the Social Security Administration website. It’s suggested that you do this 3 months before turning 65.

When do I enroll?

Remember, if you are receiving Social Security benefits, you will be auto enrolled. If not, it’s important to note that time is of the essence. The Initial Enrollment Period, or IEP, for Medicare spans across seven months: the month of your birthday as well as three months before and three months after. There are penalties if you do not enroll in this window, and you may be stuck paying higher premiums forever, so it’s very important to start early and not be late!

According to AARP, it’s important to do some homework before this enrollment. Some things to consider when selecting the best package include whether or not your desired doctors will still be able to be seen once on Medicare. Making a list of any medications will also help you select the best plan. Do you travel often or split your residency between multiple locations? If so, a plan that allows care in different states would be necessary.

Are you or someone you know under the age of 65 with a disability, chronic condition? You may still qualify. Take our quiz to discover if you are missing out on incredible benefits.

Medicare.gov is the official site for Medicare, and you can find additional information at AARP’s Medicare Made Easy.