Parts A and B are federal health insurance programs and are often used together to cover hospital and outpatient care. They're both part of Original Medicare.

Medicare Part D prescription drug coverage is offered by private insurance companies and must be purchased separately. It can be paired with Original Medicare, or with certain Medicare Advantage (Part C) plans. Most Medicare Advantage plans come with prescription drug coverage already built into the plan.

Original Medicare helps pay for hospitalization, skilled nursing and outpatient care, but it doesn't pay for everything. Medicare supplement insurance plans can help fill in the gaps. They're offered by private insurance companies, so plans vary by state and you may have many choices. Be sure to check what's available in your area.

Medicare Advantage plans include the same benefits as Medicare Part A and Medicare Part B, and may include extras like eyeglasses, dental coverage, hearing coverage or even gym memberships. In many cases, they also include prescription drug coverage (Medicare Part D). Because these plans are offered by private insurance companies, plans will vary, so compare carefully.

Original Medicare is a federal health insurance program and provides the same coverage no matter where you live.

Medicare Advantage, Medicare Part D and Medicare supplement insurance plans are issued through private insurance companies, so different plans will be available in each state. Medicare supplement insurance plans and benefits are standardized by federal law, so every insurer’s Medicare supplement insurance Plan A is identical to every other insurer’s Plan A, and the same for every other Medicare supplement insurance plan in turn. The exceptions are Massachusetts, Minnesota and Wisconsin (known as the “waiver” states), which have their own standardized plans.

If you have employee, retiree or union health care coverage, check with your plan administrator to discuss the best arrangement for your situation. You may want to sign up for Medicare Part A regardless of having other coverage, since it's usually premium free.

You can choose to disenroll from Medicare Part B when you're first eligible to delay having to pay the Part B premium. If this is the case, you can sign up for Part B during the Special Enrollment Period (SEP) after your employer coverage ends. Your SEP is 63 days from the day you retire or lose your employer health insurance, whichever comes first.

It's possible that your current plan complements what you'll get with Medicare. In any case, you don't need to give up your outside coverage once you enroll in Medicare.

For most people, you're eligible to first enroll in Medicare during your Initial Enrollment Period (IEP), 3 months before your 65th birth month*, during your birth month, and 3 months after your birth month. If you miss your IEP, there are still opportunities to enroll, but you may pay higher premiums or have fewer plan choices unless you qualify for an exception.

*If your birthday is on the first day of the month, your Part B coverage will start the first day of the prior month. If this is true for you, use the month before you turn 65 as your birth month.

Learn more about enrollment by exploring this site.

• Medicare Part A Enrollment
• Medicare Part B Enrollment
• Medicare Advantage (Part C) plans
• Medicare Part D Enrollment
• Enrollment Road Map

You have an OEP for Medicare supplement insurance in all states that begins when you are first enrolled in Medicare Part B at age 65 or older. It begins the month you enroll in Part B and ends six months later. Many states provide an OEP for beneficiaries under age 65, which begins the month you enroll in Medicare Part B and ends six months after. You can apply for a Medicare supplement insurance plan at any time after your OEP as well, but you could be denied coverage or pay a higher premium.

You can change your plan choices without penalty during the AEP each year, so it's a good idea to review your coverage annually. (You may also switch from a Medicare Advantage plan back to Original Medicare from Jan. 1st through Feb. 14th.)