Medicare is a federal health insurance program that consists of several parts, including parts A and B (original Medicare). At the end of 2016, about 67 percent of people enrolled in Medicare were using original Medicare.

Medicare Part A is hospital insurance. But who exactly is eligible for it? To meet the basic eligibility requirements for Part A, a person must be a citizen or permanent resident of the United States and also be one of the following:

There’s even more to learn about Medicare Part A. Continue reading as we delve deeper into this part of Medicare, its eligibility requirements, and much more.

Medicare Part A is hospital insurance. It covers inpatient stays at the following:

The following things are typically covered as part of an inpatient stay at one of the above facilities:

  • a semiprivate room
  • meals
  • general nursing care
  • medications necessary for your inpatient care
  • other medically necessary services and supplies

You must be admitted as an inpatient at one of these facilities to be covered under Part A. If you’re not formally admitted as an inpatient, the services received will be considered outpatient care.

Because of this, it’s always important to ask your doctor or caregiver if you’re an inpatient or an outpatient on each day. This can have implications for which parts of your stay are and are not covered under Part A.

Typically, many people who enroll in Part A are age 65 and older. However, some specific groups of people younger than 65 years old may also be eligible for Part A. These groups include people with:

Some people will be automatically enrolled in parts A and B, while others will have to sign up. You’ll be automatically enrolled if:

  • You’re already receiving Social Security or Railroad Retirement Board (RRB) benefits: You’ll be automatically enrolled on the first day of the month you turn age 65 if you’ve been receiving these benefits at least 4 months before your birthday.
  • You’re less than 65 years old and have a disability: You’ll be automatically enrolled after receiving Social Security or RRB disability benefits for 24 months.
  • You have ALS: You’ll be automatically enrolled the month that you’re eligible to receive Social Security or RRB disability benefits.

People who aren’t receiving Social Security or RRB benefits or who have ESRD will have to sign up for Medicare. This can be done through the Social Security Administration website.

If you can’t receive premium-free Part A, you’ll have to pay a late enrollment penalty if you don’t buy Part A when you’re first eligible. In this case, your monthly premium can go up by 10 percent.

You’ll be subject to this higher premium for double the amount of years that you were eligible but didn’t enroll. For example, if you enroll 1 year after you were eligible, you’ll pay the higher monthly premium for 2 years.

Below are some important deadlines related to Medicare parts A and B to keep in mind:

Initial enrollment: Your 65th birthday

If you’re eligible for Medicare parts A and B when you turn 65 years old, initial enrollment consists of a 7-month period that includes:

  • the 3 months before your 65th birthday
  • the month of your 65th birthday
  • the 3 months after your 65th birthday

If you won’t be automatically enrolled in Medicare parts A and B when you turn age 65, you can sign up at any time during initial enrollment. When your coverage starts will depend on when you sign up.

In addition to parts A and B, you can also sign up for a Part D (prescription drug coverage) plan during this time.

General enrollment: January 1 to March 31

During this time, you can sign up for parts A and B if both of the following are true:

  • You didn’t sign up when you were initially eligible (during initial enrollment).
  • You can’t enroll during a special enrollment period.

If you enroll during general enrollment, your coverage will begin on July 1. You’ll have to pay a premium for parts A and B and may also be subject to a late enrollment penalty.

During this time, you can also switch from a Part C (Medicare Advantage) plan back to original Medicare (parts A and B).

Medicare Advantage open enrollment: April 1 to June 30

If you enrolled in Medicare parts A and B for the first time during general enrollment, you can add a Part D plan during this time. Your coverage will begin on July 1.

Open enrollment: October 15 to December 7

During this time period, anyone with Medicare parts A and B can change to a Part C plan or add, switch, or remove a Part D plan. New coverage will begin on January 1.

Special enrollment

If your initial enrollment period has passed, you may be able to sign up for parts A and B during a special enrollment period. You can do this if you’re covered under a group health plan provided by your employer. You can sign up:

  • anytime when you’re covered by the group health plan
  • in the 8 months following the end of employment or the end of coverage by the group health plan

  • Medicare Part A is hospital insurance and is part of original Medicare. Generally speaking, you’re eligible for Part A if you’re age 65 or older, have a disability, or have ESRD or ALS.
  • Some people will be automatically enrolled in Part A, while others will have to sign up.
  • Pay attention to important Medicare deadlines to ensure that you sign up for coverage when you’re eligible.

This article was updated on November 20, 2020, to reflect 2021 Medicare information.


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