When does Medicare coverage start?

Medicare is a federally funded health insurance program that provides coverage for seniors and people with certain disabilities. The program helps to pay for hospital stays, doctor visits, and prescription drugs. In many cases, Medicare coverage starts when the beneficiary turns 65 years old. However, there are some exceptions.

There are many factors that can affect your Medicare enrollment and coverage start dates. This includes when you first become Medicare-eligible and the enrollment period you use at the time of enrollment. 

Medicare start dates by enrollment period
Enrollment period	When to sign up	Effective date	Considerations	Learn more
Initial Enrollment Period for people who turn 65 years old	Starts 3 months before your 65th birthday and ends 3 months after you turn 65.	Medicare coverage always starts on the 1st of the month after the month enrolled. See details here.	If you miss your Initial Enrollment Period, you may have to wait to sign up and pay a monthly late enrollment penalty. Penalties also may apply if you must pay a Part A premium. Not everyone needs to enroll in Medicare at 65, i.e., people who are still working.	Learn more
Initial Enrollment Period for younger people with a qualifying disability, ALS, or ESRD	If you’re on SSD, you are automatically enrolled in month 25 of receiving SSD. If you have ALS and SSD, you get enrolled in month 1 of receiving benefits. If you have ESRD, it varies by situation.
General Enrollment Period	Jan. 1 to Mar. 31	First day of the following month in which you enrolled	You might pay a monthly late enrollment penalty if you don’t qualify for a Special Enrollment Period.	Learn more
Annual or Open Enrollment Period	Oct. 15 and Dec. 7.	Jan. 1	This is the best time to make changes to existing Medicare health and drug coverage.	Learn more
Supplement Open Enrollment Period	Starts the first of the month you turn 65 and enrolled in Part B and lasts 6 months.	Coverage becomes effective the first of the following month after you enroll.	During this time, you’ll have guaranteed issue rights, meaning a carrier cannot deny you coverage or charge you a higher premium due to a pre-existing condition.	Learn more
Medicare Advantage Open Enrollment Period	Jan. 1 to Mar. 31	New coverage begins the 1st of the month after your new plan gets your request for coverage.	The Medicare Advantage Open Enrollment Period isn’t for people who already have Original Medicare.	Learn more
Special Enrollment Period	Varies by qualifying event.	Typically, coverage starts the month after you sign up.	Find a list of special circumstances here.	Learn more

Initial Enrollment Period

The Initial Enrollment Period (IEP) is a person’s first chance to sign up for Medicare. Each person’s Medicare Initial Enrollment Period is specific to them. Your Initial Enrollment Period will begin three months before the month of your 65th birthday and end three months after your 65th birthday month. Generally, your coverage will begin the first day of the month before you turn 65.

For example, if your birthday is in January, then your Initial Enrollment Period will begin on the first of October and end on the last day of April. If you enroll in Medicare during October or November, your coverage starts the first day of December.

When does Medicare coverage start for ESRD?

Eligibility for Medicare is linked to your End-Stage Renal Disease diagnosis. This means that if you have been diagnosed with ESRD, there is no waiting period to enroll once your physician prescribes a regular course of dialysis or a kidney transplant.

Most of the time, Medicare coverage for someone who’s been diagnosed with ESRD will begin on the first day of the third month following the month when they start their regular dialysis.

Please note that Medicare sometimes waives the three-month waiting period if they:

• Have a kidney transplant that falls within those three months
• Participate in a self-dialysis training program

When does Medicare coverage start for ALS?

If you have been diagnosed with amyotrophic lateral sclerosis (ALS), commonly known as Lou Gehrig’s Disease, you’re eligible for automatic enrollment into Medicare the first month you receive Social Security Disability Insurance (SSDI).

Social Security Disability Benefits

Except for ESRD and ALS, all other disabling diagnoses will qualify you for Medicare once you’ve collected Social Security Disability Insurance for 24 months. At the end of the 24 months, you’ll be automatically enrolled in Parts A and B.

After you’re enrolled in Part B, you can then choose to enroll in either a Medicare Advantage plan or remain in Original Medicare and possibly enroll in a Medicare supplement insurance plan in addition to a Part D drug plan.

Medicare late enrollment penalties

When you don’t enroll in Medicare during your Initial Enrollment Period, and you don’t have another form of creditable coverage, then you may be faced with penalties. These penalties could last your lifetime and be added to your monthly premium. However, the penalties can be eliminated in various ways by meeting certain criteria. 

For Medicare Part B, your penalties will start to accumulate once you go longer than 12 months before enrolling when you were first eligible without having another form of creditable coverage. The late enrollment penalty is 10% of the standard monthly premium for every 12 months you go without health coverage. 

For example, if you were eligible for Medicare in March of 2018 but didn’t enroll until January of 2021 and had no other form of creditable coverage, then your penalty in 2024 would be $39.94, giving you a grand total of $209.64 since you went a full 24 months without coverage. ($174.70 x 0.2 = $39.94) ($174.70 + $39.94 = $209.64)

For Medicare Part D or your prescription drug coverage, Medicare calculates the penalty by multiplying 1% of the National Base Beneficiary Premium ($34.70 in 2024 and $36.78 in 2025) times the number of full, uncovered months you didn’t have Part D or creditable coverage. The monthly premium is rounded to the nearest $0.10 and added to your monthly Part D premium.

RELATED: How to avoid the Medicare Part D penalty

Medicare General Enrollment Period

For those who didn’t enroll in Medicare Part A (hospital insurance) and Part B (outpatient insurance) during their Initial Enrollment Period, the next enrollment period you can use to enroll in Part A and Part B is the General Enrollment Period. 

The General Enrollment Period occurs annually between Jan. 1 and Mar. 31. Your coverage will begin the first day of the following month in which you enroll. The general enrollment period is only for Part A and Part B, it is not to enroll in Medicare Part C (Medicare Advantage) or Part D (prescription drug coverage).

Medicare Annual Enrollment Period or Open Enrollment Period

The Medicare Annual Enrollment Period, commonly referred to as the Open Enrollment Period, occurs annually between Oct. 15 and Dec. 7. Your coverage will become effective on Jan. 1 of the following year.

During this enrollment period, you can make changes to your current Medicare Advantage or Part D prescription drug plan. You can enroll, switch, or disenroll from a plan. 

This enrollment period is not to enroll in Medicare Part A or Medicare Part B coverage for the first time. It’s also not for enrolling in a Medicare Supplement plan. Although, you can enroll in a Medicare Supplement plan during this time if you choose to do so. However, unless it overlaps with your Medicare Supplement Open Enrollment Period, you’ll have to go through medical underwriting. 

Medicare Supplement Open Enrollment Period

Your Medicare Supplement Open Enrollment Period is not annual. It’s a one-time enrollment window that begins the first of the month you’re 65 and enrolled in Part B. This enrollment window will last six months. 

During this time, you’ll have guaranteed issue rights. This means a carrier cannot deny you coverage or charge you a higher premium due to a pre-existing condition. Your coverage will become effective the first of the following month after you enroll.

The only time you’ll have more than one Medicare Supplement Open Enrollment Period is if you first became eligible for Medicare due to a disability. In this scenario, your first Medicare Supplement Open Enrollment Period will begin once you have been collecting SSDI for at least 24 months and enrolled in Part B. Your second Medicare Supplement Open Enrollment Period will begin when you turn 65 years old. 

However, there are some states with different policies for Medigap plans. Some states, like New York, have year-round Medicare Supplement open enrollment. 

Medicare Advantage Open Enrollment Period

The Medicare Advantage Open Enrollment Period occurs annually between Jan. 1 and Mar. 31. It overlaps with the General Enrollment Period, but please note they are two different enrollment periods completely.

The Medicare Advantage Open Enrollment Period is only for those who are currently enrolled in a Medicare Advantage plan and want to make changes. It’s a second chance for those Medicare beneficiaries who enrolled in a Medicare Advantage plan during the Medicare Annual Enrollment Period in the fall, and when they went to use their Medicare benefits the following year, they were unhappy with the coverage.

When does Medicare Advantage coverage start? Your Medicare Advantage coverage will start the first of the following month after you enroll if you signed up during the MA OEP.

Special Enrollment Period

If you have a change in circumstance, you could be eligible for a Special Enrollment Period. There are many types of Special Enrollment Periods for Medicare. 

Examples of Special Enrollment Period qualifying circumstances:

• You lost your employer group coverage
• You moved to another state
• You moved back to the United States
• You left your Medigap plan to sign up for Medicare Advantage
• Your plan left your service area
• You were released from jail
• A 5-star Medicare Advantage plan option becomes available in your area
• No longer qualify for Extra Help
• No longer eligible for Medicaid

You lost your employer group coverage

You’re eligible for a Special Enrollment Period if you lost your employer group coverage. This Special Enrollment Period will last a total of eight months with a coverage effective date the first of the following month after you enroll. 

You’ll need to complete two forms:

• CMS 40B
• CMS L564

The CMS L564 form will need to be completed by your employer. You can also upload the completed forms to your My Social Security account.

You moved to another state

Since Medicare Part A and Part B travel with you, you won’t need to make any changes to your coverage. You’ll only need to notify Social Security of your new mailing address. 

If you move to a different state with Medicare Advantage or Medicare Part D, your Special Enrollment Period begins the month you move and extends for two months after. If you notify your insurance company after you move, then your Special Enrollment Period begins the month you notify the carrier and ends two months after. Your coverage will become effective the first of the following month after you enroll.

You moved back to the United States

If you were living in another country and moved back to the United States, you’ll have a Special Enrollment Period that will last two months, beginning from the date you moved back. Your coverage will become effective the first of the following month after you enroll.

You left your Medigap plan to sign up for Medicare Advantage

Trial Rights Special Enrollment Period is a one-time SEP for beneficiaries who left a Medigap plan to enroll in a Medicare Advantage plan. You’ll have 12 months from the effective date of your Part C plan to drop it and enroll back into Original Medicare and Medigap. 

You can only enroll in a Medigap plan of equal or lesser value. For example, if you had Plan G, you could enroll in Plan G or a letter plan with fewer benefits. This means you cannot enroll in Plan F since Plan F has more benefits than Plan G. Your coverage will become effective the first of the following month after you enroll.

You were released from jail

If you were incarcerated, you’d qualify for a Special Enrollment Period. This SEP will allow you to enroll in a plan upon being released and will end two months later. Your coverage will become effective the first of the following month after you enroll.

A 5-star Medicare Advantage plan becomes available in your area

If a 5-star Medicare Advantage plan becomes available in your area, you can enroll if you enroll between Dec. 8 and Nov. 30. Your coverage will become effective the first of the following month after you enroll.

No longer qualify for Extra Help

Extra Help is a safety net for those considered low-income. If you’re no longer eligible for Extra Help, you’ll have three months from the date you were no longer eligible to enroll in another Medicare Part D or Medicare Advantage prescription drug plan.

Medicare enrollment FAQs

Can I sign up for Medicare before turning 65?

Yes, you can sign up for Medicare before turning 65 if you are diagnosed with ESRD or ALS or you have been collecting SSDI for 24 months. 

Do I automatically get Medicare when I turn 65?

You’ll only automatically get Medicare when you turn 65 if you’re collecting Social Security benefits. Otherwise, you’ll have to manually enroll in Part A and Part B during your Initial Enrollment Period. 

What happens if you don’t sign up for Medicare at 65?

If you don’t sign up for Medicare at 65 and you don’t have another form of creditable coverage, such as group employer coverage, then you could face penalties under Medicare Part B and Medicare Part D. Some exceptions include collecting Social Security disability income before turning 65, getting Extra Help or a Medicare Savings Program, and if you can document that you received incorrect or poor information regarding credible coverage. 

Should I sign up for Medicare if I’m still working?

Regardless of if you’re still working and have a group health plan, you should still enroll in Medicare Part A coverage. Premium-free Part A will give you extra hospital benefits. However, with Medicare Part B enrollment, if you have group employer coverage, then you can delay enrolling until you leave your group coverage insurance. 

Are you automatically enrolled in Medicare if you are on Social Security?

Yes, you will automatically be enrolled in Medicare if you’re collecting Social Security benefits at the time you turn 65. If you want to delay enrollment, you’ll need to contact Medicare directly. 

How do I know if I’m automatically enrolled in Medicare?

You’ll know if you’re automatically enrolled in Medicare when you receive your Medicare card a month before your 65th birthday. 

Can I change my Medicare start date?

Yes, you may be able to change your month of enrollment either by amending your application or by submitting a new Part B application form through your My Medicare account.

I changed Medicare plans. When does my new plan activate?

This depends on what enrollment period you were eligible for to make changes. If you changed your plan during the Annual Enrollment Period in October, then your coverage will begin on Jan. 1 of the following year. If you made changes during a Special Enrollment Period, then your coverage should become effective the first day of the month after you enroll.