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When Does Medicare Coverage Start?

In general, Medicare starts at age 65 for most eligible seniors. However, some people with qualifying disabilities or who meet other special circumstances may experience different activation times.  Examples include:

  • People with ESRD (End-stage Renal Disease): Coverage begins on the first day of the fourth month of dialysis treatment.
  • People with ALS (Amyotrophic Lateral Sclerosis): Coverage begins on your first month of receiving Social Security Disability Insurance (SSDI).
  • People who receive Social Security benefits due to another qualifying disability: Automatically enrolled in Medicare on your 25th month of SSDI.
  • People attempting to enroll in Medicare Advantage: Coverage begins the first of the following month after you officially request it during the MA open enrollment period.

How Does Medicare Enrollment Work? 

Though many seniors automatically see initial enrollment in Medicare at age 65, other prospective members will have to enroll during set enrollment periods and meet all Medicare eligibility requirements.

Medicare Eligibility Requirements 

While everyone becomes eligible for Medicare at age 65, certain disabled individuals can enroll earlier. For example, regardless of age, anybody receiving SSDI will become eligible for Medicare in the first month of their third year of benefits. Similarly, people with ALS (also known as Lou Gehrig’s disease) become Medicare-eligible as soon as they secure SSDI. Individuals with permanent kidney failure become Medicare-eligible within months of their first dialysis treatment or hospitalization for a transplant.

Anyone with these disabilities would also qualify for Medicare Advantage before reaching 65. Medigap eligibility for disabled individuals, however, varies from state to state. Not all states will allow enrollment before your 65th birthday.

Medicare Enrollment Periods 

You can apply for or update your Medicare policy during one of many enrollment periods relative to your situation and desired coverage. These periods include:

  • Initial enrollment: First-time and typically automatic registration for 65-year-olds or those with qualifying disabilities
  • General Enrollment: For people who missed their initial enrollment
  • Annual enrollment: Yearly window to make changes to existing policies
  • Supplement Open Enrollment: For individuals seeking or wanting to change their Medigap coverage
  • MA Open Enrollment: For individuals who want to change their Medicare Advantage policies
  • Special Enrollment: For people who missed conventional enrollment periods due to approved circumstances
Enrollment Period
What You Need to Know
Starts 3 months before and ends 3 months after your 65th birthday. Varies for people with qualifying disabilities.
Not everyone, particularly non-retired individuals, needs to enroll at age 65.
General Enrollment period
Jan 1-Mar 31
You may have to pay a late enrollment penalty for missing your IEP and enrolling during GEP.
Oct 15-Dec 7
Best time to make annual changes to your existing Medicare plan.
Medigap Initial Enrollment
Six-month window begins once you have turned 65 AND have enrolled in Part B.
During this time you have guarantee issue rights, meaning insurers cannot deny coverage or raise premiums for a pre-existing condition.
Medicare Advantage Open Enrollment
Jan 1-Mar 31
Only applies to people with MA who want to change their current plan.
Special Enrollment Period
Varies by qualifying event

What is Automatic Medicare Enrollment? 

If you have already claimed Social Security benefits, Original Medicare will automatically enroll you on the first day of the month you turn 65. Part A automatic enrollment only applies to people who have worked long enough and paid their share of Medicare tax to qualify for a premium-free plan.  

Medicare will automatically enroll people with qualifying disabilities on their 25th month of SSDI or Railroad Retirement Board (RRB) benefits. Individuals with ALS will automatically receive coverage on their first month of SSDI.

When Does Medicare Advantage Start? 

Medicare Advantage coverage begins relative to your care eligibility and your enrollment date. As with Original Medicare, if you qualify for and enrolled in Medicare Advantage during your IEP, you should receive coverage starting the first of the month following enrollment. If you registered during the GEP, coverage starts July 1st. If enrolled during the AEP, coverage begins January 1st.

The Medicare Advantage Open Enrollment period offers a second annual opportunity to change or update MA plans between Jan 1st and March 1st. Anyone who enrolls in MA during this time will begin receiving coverage on the 1st of the month after their new insurer gets their request.

When Does Coverage Start For Non-traditional Medicare Recipients? 

If you have a qualifying disability, you may begin receiving Medicare earlier than most people. Commonly, this includes people with ALS, ESRD, or individuals already receiving Social Security disability benefits.

Medicare Start Times for Individuals With ALS 

If you have ALS, you become eligible for Medicare enrollment as soon as you first receive SSDI or a railroad disability annuity check. After you have submitted an application for SSDI or a railroad disability annuity, you must endure a five-month waiting period before benefits commence. As long as you explicitly state that you have ALS on your SSDI or railroad application, your Medicare coverage should automatically begin in the same month as your disability benefits.

Medicare Start Times for Individuals With ESRD 

If you have ESRD and have already applied for Medicare, coverage will begin on the first day of your fourth month of dialysis treatment. If you have scheduled a kidney transplant, Medicare coverage will start the same month a Medicare-certified hospital admits you for a transplant as long as the procedure occurs within the next two months. If your transplant gets delayed, so will your Medicare start date.

Eligibility for Medicare based on ESRD allows for special 12-month retroactive coverage unavailable for most other beneficiaries. For example, suppose you become eligible for Medicare due to ESRD in January but don’t sign up for coverage until December of the same year. In that case, your coverage will still reimburse charges from January on. 

Medicare Start Times for Individuals with Social Security Disability Benefits 

If you receive SSDI, you will automatically begin receiving Medicare on your 25th month of benefits, regardless of age. This 24-month qualifying period can occur as one long stretch or combined eras of disability benefits, given those timeframes meet SSA criteria. If your disability persists, you should continue receiving Medicare, even if you decide to return to work.

To qualify for SSDI, you must have worked jobs covered by Social Security and exhibit a medical condition that meets Social Security’s strict definition of a disability. To apply for disability benefits, complete an application online, call Social Security, or visit your local SSA office.

What Happens If Miss Your Opportunity to Enroll 

If you miss your initial Medicare enrollment period and do not qualify for special enrollment, you will likely have a late enrollment penalty. Medicare created these penalties to encourage beneficiaries to enroll in coverage during their IEP. While late enrollment penalties exist across the Medicare spectrum, they vary depending on your coverage type and how long you wait to apply.

Late Enrollment Penalties for Original Medicare 

If you fail to enroll in Original Medicare during your IEP, a late enrollment penalty gets added to your monthly premium for as long as you retain coverage. The Medicare Part B penalty increases by 10% for every eligible year you fail to secure coverage.

If you do not qualify for premium-free Part A and forget to purchase it during your IEP, your Part A premium can increase by 10%. You’ll have to pay this penalty for twice the number of years you waited to enroll. So if you qualified for Part A but took two years to sign up, you’ll have to pay a 10% penalty on your Part A premium for the next four years.

Late Enrollment Penalties for Medicare Advantage 

Medicare Advantage, or Medicare Part C, offers Part A and Part B benefits and often incorporates some prescription drug coverage (Part D). Because private companies govern Medicare Advantage policies, they can vary in price and coverage depending on who you insure with.  

Medicare Advantage plans do not impose late enrollment penalties. However, many people initially begin Medicare coverage with OM and then switch to MA later on. If you failed to enroll in Medicare Part A and B on time and switched to Medicare Advantage years later, you would still pay penalties in the interim. These penalties would remain should you ever change back to Original Medicare.

Late Enrollment Penalties for Part D 

If you have creditable prescription drug coverage (any outside coverage equal in value to Medicare Part D) or qualify for “Extra Help”, a Medicare program that pays Part D expenses for limited-income individuals, you do not have to worry about Part D late enrollment penalties. However, if you do not sign up for Part D when first joining Medicare or go without a creditable prescription drug plan for over 63 days, you must pay an extra 1% penalty for each unregistered month. 

Suppose your monthly Part D premium is $35, and you fail to enroll in Part D for 20 months. You would assess a recurring 20% penalty, making your new recurring premium $42 as long as you continue receiving coverage.

How To Take Advantage of Your Medicare Enrollment Period 

Regardless of when or how you register for Medicare or make changes to an existing policy, take these precautions to guarantee the most out of your next year of coverage:

  1. Know your eligibility status and whether you qualify for automatic enrollment based on your age or disability.
  2. If enrolling in Medicare for the first time, sign up for Part A, B, and D promptly to avoid a recurring late penalty.
  3. Review your current plan and utilize the annual enrollment periods to adjust coverages or switch policy types.
  4. Contact Medicare to see if you qualify for special enrollment periods that could save you from late fees or coverage gaps.

How Do You Know Your Medicare Coverage Is Active? 

The date your Medicare coverage becomes active depends on when you enroll.  

If you sign up for Medicare…
Your coverage starts
3, 2, or 1 month before turning 65
The first day of your birthday month
The month you turn 65
One month after you sign up
1, 2, or 3 months after you turn 65
The first day of the month after you sign up
During the GEP (Jan 1-Mar 31)
July 1st
During a SEP
The next month

If you have questions about when your plan might become active, you can call 1-800-MEDICARE or log into to review your policy status at any time. Once you confirm that coverage has begun, you can actively start seeing doctors, receiving services, and purchasing prescription drugs.

When Does Your Coverage Start if You Change Plans? 

Generally, you can only change your Medicare plan during one of the following periods. Depending on which window applies to you, coverage would start accordingly:

Medicare enrollment period
Coverage starts
Annual or open enrollment (Oct 15-Dec 7)
January 1st.
Medicare Advantage open enrollment (Jan 1-Mar 31)
The first of the month after your new carrier receives your request.
Supplement open enrollment
The first day of the month after you enroll.
Any special enrollment period
Typically, coverage starts one month after enrollment.

Usually, your old coverage will remain active until your new plan takes over. As with initial enrollment concerns, contact Medicare directly to verify your status and determine the best foot forward.

Putting It All Together 

If you have recently become eligible for Medicare due to your age or a particular disability, ensure you register for coverage immediately to avoid costly late fees or going without medical insurance. If you do not qualify for automatic enrollment, you can sign up within three months of your 65th birthday or after three months of receiving ESRD dialysis treatment.

If you already have Medicare and want to change plans, you can do so during one of the annually recurring Medicare open enrollment periods. Your coverage start date will vary relative to your eligible enrollment window. Once coverage begins, you can see in-network doctors and receive Medicare-approved services for reduced out-of-pocket costs.

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