When will Medicare coverage start?

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It varies depending on when you signed up for Medicare. Check out the Medicare website for details.

It also varies depending on what Medicare coverage you are getting:

Medicare Part A (hospitalization)
Medicare Part B (medical)
Medicare Part C (Medicare Advantage)
Medicare Part D (prescription drug coverage)
Medicare Supplement (Medigap)

When will Medicare Part A and Part B coverage start?

If you sign up during the Initial Enrollment Period,

Your coverage start date depends on your birthday if both of these apply:

You sign up for Medicare Part A (Hospital Insurance) and/or Medicare Part B (Medical Insurance).
You sign up during the first 3 months of your Initial Enrollment Period.

Your coverage starts the first day of the month you turn 65, unless your birthday is on the first day of the month.
For example, if your birthday month is October and you sign up in the Initial Enrollment Period (July, August, September) then your coverage starts on October 1.
Or, if your birthday month is October and your birth date is October 1 and you sign up in the Initial Enrollment Period (June, July, August) then your coverage starts on September 1.

If you sign up for Medicare the month you turn 65, your birthday month: coverage will start 1 month after you start up. If you birthday month is October, your Medicare coverage will start in November. If you sign up during the last 3 months of the Initial Enrollment Period, you Medicare coverage will start later. See the Medicare “When will my coverage start?” information.

If you sign up during a Special Enrollment Period or a General Enrollment Period, you will have to check with Medicare/Social Security to determine when coverage begins. For the General Enrollment Period coverage usually started July 1. However, effective January 1, 2023, General enrollment Period coverage starts the month after you sign up. For the Special Enrollment Period coverage usually starts he month after you sign up.

When will Medicare Advantage (Part C) coverage start?

If you elect to use Medicare Advantage (an HMO/PPO type plan, not Original Medicare), and you sign up during the Initial Enrollment Period, coverage starts similar to Medicare Part A and B.

Check out the Medicare “Joining a health or drug plan” information, “When to join a Medicare Health or Drug Plan section. There are items for the different periods to sign up for Medicare Advantage (Part C ) on this same page.

According to this Medicare information page, if you sign up for Medicare Advantage (Part C) during the first 3 months of your Initial Enrollment Period, coverage starts the first day of the month you turn 65, the same as when Medicare starts. If you sign up the month you turn 65 or during the last 3 months of the Initial Enrollment Period, coverage starts the first day of the month after you ask to join the plan.

If you sign up during a Special Enrollment Period or a General Enrollment Period, you will have to check with Medicare/Social Security to determine when coverage begins.

When will Medicare Drug coverage (Part D) coverage start?

If you elect to include Medicare Part D (prescription drug coverage), and you sign up during the Initial Enrollment Period, coverage starts similar to Medicare Part A and B.

According to this Medicare information page, if you sign up for Medicare Drug Plan (Part D) during the first 3 months of your Initial Enrollment Period, coverage starts the first day of the month you turn 65. If you sign up the month you turn 65 or during the last 3 months of the Initial Enrollment Period, coverage starts the first day of the month after you ask to join the plan.

If you sign up during a Special Enrollment Period or a General Enrollment Period, you will have to check with Medicare/Social Security to determine when coverage begins.

When will Medicare Supplement (Medigap) coverage start?

Here is a good publication from Medicare covering Medicare Supplement plans (Medigap).
2024 Choosing a Medigap Policy – A Guide to Health Insurance for People with Medicare.
There is no comparable 2025 document to be found for Choosing a Medigap Policy.

Use the Medicare “How to compare Medigap policies” website for information.

It is critical to enroll for Medicare Supplement coverage (Medigap) during the Open Enrollment Period, if you are not using Medicare Advantage and want supplemental coverage. If you do not, you may not get a policy, and, if you do get a policy, it will probably cost a lot more.

Review this page for information to Find a Medigap Policy that works for you. From this link you will enter your zip code and some brief information about yourself (age, sex, and whether or not you use tobacco). A list of the Plan types (A through N) will appear. You can then select the View Policies link button for each of the Plan types (A through N) to see a list of the insurance providers plan offerings with estimated cost for the Plan type (A through N).

It has been noted that Plan type G (Plan G) has the best coverage, whereas Plan type N (Plan) has the second best coverage.

Once you have researched the Medigap options and used the Find a Medigap Policy tool, you will then and contact your chosen provider (insurance company) in advance of the open enrollment period. It can take 10-15 business days, or longer, to have Medigap approved, date of application, card in hand. It is advisable to do it at least three weeks in advance.

When buying Medicare Supplement (Medigap) coverage, you will fill out an application.

Review the “When to enroll for Medicare Supplement Coverage (Medigap)” topic for more information on enrolling for Medicare Supplement Coverage (Medigap).

You will then pay for the policy.

During the process of enrolling and paying, “ask for your Medigap policy to become effective when you want coverage to start (e.g. the month you turn 65 or the month after you turn 65). Generally, Medigap policies begin the first of the month after you apply. If, for any reason, the insurance company won’t give you the effective date for the month you want, call your State Insurance Department.”

During the Open Enrollment Period for Medicare Supplement plans (Medigap), an insurance company can’t use medical underwriting. This means the insurance company can’t do any of these because of your health problems:
• Refuse to sell you any Medigap policy it offers
• Charge you more for a Medigap policy than they charge someone with no
health problems
• Make you wait for coverage to start (except as explained below)

“While the insurance company can’t make you wait for your coverage to start, it may be able to make you wait for coverage related to a pre-existing condition. A pre-existing condition is a health problem you have before the date a new insurance policy starts. In some cases, the Medigap insurance company can refuse to cover your out-of-pocket costs for these pre-existing health problems for up to 6 months. This is called a “pre-existing condition waiting period.” After 6 months, the Medigap policy will cover the pre-existing condition.”

“Coverage for a pre-existing condition can only be excluded if the condition was treated or diagnosed within 6 months before the coverage starts under the Medigap policy. This is called the “look-back period.” Remember, for Medicare-covered services, Original Medicare will still cover the condition, even if the Medigap policy won’t, but you’re responsible for the Medicare coinsurance or copayment.”

“If you have a pre-existing condition and you buy a Medigap policy during your Medigap Open Enrollment Period and you’re replacing certain kinds of health coverage that count as “creditable coverage,” it’s possible to avoid or shorten waiting periods for pre-existing conditions. Prior creditable coverage is generally any other health coverage you recently had before applying for a Medigap policy. If you’ve had at least 6 months of continuous prior creditable coverage, the Medigap insurance company can’t make you wait before it covers your pre-existing conditions.”

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