What is Medicare Supplement

Medicare Supplement Insurance — also known as Medigap — is private insurance that helps pay the “gaps” in Original Medicare (Parts A and B).
It is designed to cover out-of-pocket costs such as deductibles, copayments, and coinsurance that Medicare doesn’t pay.

Medigap policies are standardized and regulated by the Centers for Medicare & Medicaid Services (CMS) and are offered by private insurance companies.

Each Medigap plan is identified by a letter (A, B, C, D, F, G, K, L, M, N) and offers a different level of coverage, but the benefits for each lettered plan are identical across all insurers.

    Medicare Supplement Coverage

    Medigap Covered Services

    • Part AHospital & Inpatient Services:
      • Inpatient hospital costs and coinsurance, plus up to 365 additional days after Medicare benefits are used.
      • Part A deductible.
      • Hospice care coinsurance or copayments.
      • Skilled Nursing Facility (SNF) coinsurance.
      • Blood (first 3 pints each year).
      • Foreign travel emergency coverage (up to plan limits).
    • Part BMedical & Outpatient Services:
      • Part B coinsurance or copayments for medical services.
      • Part B deductible (covered only by Plans C and F; not available to new enrollees after January 1, 2020).
      • Part B excess charges (100% covered by Plans F and G).

    Medigap Non-Covered Services

    Medigap policies do not cover everything. They generally do not include: 

    • Prescription drug coverage (Part D). If you want prescription drug coverage, you must enroll in a separate Medicare Part D plan.
    • Routine dental, vision, or hearing services.
    • Long-term or custodial care.
    • Private-duty nursing.
    • Services not approved by Medicare.

    Medicare Supplement Eligibility

    You are eligible to buy a Medigap policy if:

    • You are enrolled in Medicare Part A and Part B.
    • You are 65 or older (some states allow Medigap for people under 65 with disabilities or ESRD).
    • You live in the plan’s service area.

    You must continue paying your Part B premium in addition to your Medigap premium.

    Medicare Supplement Standardized Plans

    Medicare Supplement (Medigap) plans are standardized policies labeled A–N that help pay Original Medicare’s gaps (deductibles, coinsurance). For the same lettered plan, benefits are identical across insurers; what varies are premium, underwriting, rating method, and discounts—not provider networks (you can see any doctor who accepts Medicare). Medigap does not include Part D drug coverage. Due to MACRA, Plans C and F (including High-Deductible F) aren’t available to people newly eligible for Medicare on/after 1/1/2020; Plan G/HD-G are the closest alternatives. Policies are guaranteed renewable as long as premiums are paid.

    2025 Deductibles and Maximum-Out-Of-Pocket (MOOP):
    Medicare Part A Deductible = $1,620
    Medicare Part B Deductible = $257
    High-Deductible Plan F Deductible Amount = $2,870
    High-Deductible Plan G Deductible Amount = $2,870
    Plan K Maximum-Out-Of-Pocket = $7,220
    Plan L Maximum-Out-Of-Pocket = $3,610

    Medicare Supplement Premium Cost

    What is Medicare Access and CHIP Reauthorization Act (MACRA)
    It’s a federal law passed by Congress that prohibited Medigap plans from covering the Part B deductible for people newly eligible for Medicare on or after January 1, 2020, leading to the phaseout of Plans C, F, and High-Deductible F for those new beneficiaries.

    If you were newly eligible on/after 1/1/2020, you can’t buy C/F/HD-F. Most people choose Plan G (or High-Deductible G) as the closest alternative—same benefits as F except it does not pay the Part B deductible.


    Monthly Premium

    Premiums vary by plan letter, age, location, and company.
    Average monthly premiums (Michigan 2025):

    • Plan G: $130–$190/month.
    • Plan N: $100–$150/month.
    • High-Deductible Plan G: ~$50/month.

    Insurance companies use three different rating methods:

    Rating TypeHow It Works
    Community-ratedSame premium for everyone, regardless of age.
    Issue-age-ratedBased on your age when you first buy the policy;
    doesn’t increase due to age.
    Attained-age-ratedStarts low but increases as you getolder. (Most common)

    Monthly Premium Determination Factors

    Here are the main factors that drive a Medicare Supplement (Medigap) monthly premium: 

    • Age & rating method: Attained-age (rises as you age), issue-age (based on age when you buy), or community-rated (everyone pays same) — varies by state/carrier.
    • Tobacco use: Smoker rates are higher.
    • Gender & marital/household status: Where allowed, male rates can be higher; household discounts can lower premiums.
    • Health/underwriting: Outside guaranteed-issue windows, health history/height-weight can affect approval and price (or lead to a denial).
    • Enrollment timing: Applying during your Medigap Open Enrollment or a GI right avoids underwriting and sometimes yields better pricing.

    Medicare Supplement Plan Cost-Sharing

    While Medigap premiums are higher than Part C plans, they offer predictable costs and nationwide flexibility.

    Example (2025):
    If you have Plan G:

    • You pay the Part B deductible ($257) once per year.
    • After that, Medigap pays 100% of all Part A & B costs.

    No network restrictions — you can see any doctor or hospital that accepts Medicare.

    Medicare Supplement Enrollment

    When to Enroll in Medicare Supplement

    To enroll in a Medicare Supplement (Medigap) plan, you must have Medicare Parts A and B and live in the plan’s service area. The best time to enroll is during your 6-month Medigap Open Enrollment Period, which starts when you’re 65 or older and enrolled in Part B. During this time, you have guaranteed acceptance—no health questions or denials. After this window, you can still apply, but insurers may use medical underwriting and charge more or deny coverage. Some people qualify for Guaranteed Issue rights if they lose coverage or leave a Medicare Advantage plan. Plans and costs vary by state, and under MACRA, Plans C and F are unavailable to those newly eligible for Medicare after January 1, 2020.

    Enrollment PeriodWhen You Can EnrollUnderwriting Rules
    Medigap Open Enrollment Period6-month window starting the month you are 65+ and enrolled in Part BGuaranteed Issue: No health questions or denials
    Special Guaranteed Issue RightsWithin 63 days of losing certain coverage (e.g., MA plan trial right, employer coverage ends)Guaranteed Issue applies
    Outside Open EnrollmentAny time of yearMedical underwriting may apply

    Medigap Open Enrollment Period

    • What it is: It is a 6-month window that starts the first month you’re 65+ and enrolled in Part B.
    • Why it matters: You have guaranteed issue—you can buy any Medigap plan (A–N) sold in your state with no medical underwriting (no health questions, no denials).
    • Pricing: You’ll generally get the best available rate for your age/class; pre-existing conditions can’t be excluded.
    • If you delay Part B: Your 6-month window begins when Part B starts, even if that’s after age 65.
    • After it ends: You can still apply, but underwriting may apply (possible denial or higher premium) unless you qualify for a Guaranteed Issue right.
    • Under 65 (disability): Medigap availability/rules vary by state; many states offer a separate OEP at 65.

    Special Guaranteed Issue Rights

    • What it is: A limited-time right to buy certain Medigap plans with no medical underwriting (no health questions/denials).
    • When it applies (common triggers): You lose employer/retiree coverage, your Medicare Advantage plan ends or you move out of its area, you use the 12-month “trial right” after first joining MA, or your insurer misleads/stops offering coverage.
    • Deadline: You typically must apply within 63 days of the qualifying event—keep your notices/creditable coverage letters.
    • What you can buy: A subset of standardized plans allowed in your state (often A, B, D, G, K, L; C/F only if you were Medicare-eligible before 1/1/2020 per MACRA).
    • Tips: Apply promptly, submit proof of the qualifying event, and compare carriers—premiums vary by company and state even under GI rules.

    Outside Open Enrollment

    • You can doYou can apply anytime, but medical underwriting usually applies: insurers may deny coverage, rate you higher, or impose waiting periods (up to 6 months) for pre-existing conditions if you lack prior creditable coverage.
    • Exceptions: If you have a Guaranteed Issue (GI) right (e.g., losing employer/retiree coverage, MA plan ends or you move, 12-month MA “trial right”), you can enroll without underwriting—apply within 63 days.
    • State rules vary: Some states have birthday/anniversary or continuous enrollment protections.
    • Tips: Apply promptly after a qualifying event, keep documentation, and compare multiple carriers—rates and underwriting leniency differ.

    Medicare Supplement Medical Underwriting

    Medicare Supplement (Medigap) underwriting is the health-screening process most insurers use when you apply outside your one-time Open Enrollment Period (the first 6 months you’re 65+ and enrolled in Part B) or outside a Guaranteed-Issue (GI) situation. During underwriting, a carrier can review your medical history, recent conditions and treatments, medications, height/weight, tobacco use, and sometimes doctor or hospital records. Based on that review, the company may approve you, charge a higher premium, add a waiting period for pre-existing conditions (up to 6 months if you lacked recent creditable coverage), or decline the application. In GI situations—like losing qualifying employer coverage or using the “trial right” after trying an MA plan—carriers must accept you with no health questions. Some states add extra protections (e.g., birthday or anniversary rules for switching). Because rules vary by state and carrier, it’s smart to review timing and eligibility before applying.

    Underwriting AreaTypical RuleCommon Look-BackNotes
    Eligibility windowIf not in Medigap Open Enrollment or no GI right → medical underwriting requiredOEP/GI generally bypass underwriting.
    Phone interviewShort health interview often requiredCurrentConfirms application answers.
    Rx history checkCarriers review prescription fill history12–24 monthsConfirms conditions/ stability.
    MIB/recordsMay check MIB and request medical records12–24 monthsNot all carriers use MIB.
    Height/Weight (BMI)Must fall within carrier build chartCurrentOutside range → decline or rating.
    Tobacco useSmoker rates higher12 monthsSome carriers require smoke-free period for best rate.
    Recent hospitalization/ surgeryRecent inpatient stay/major surgery may decline/postpone3–12 monthsElective or pending surgery often postpones.
    Pending tests/referralsUndiagnosed symptoms or pending work-ups → postponeUntil resolvedMust have diagnosis/treatment plan.
    Oxygen useCurrent oxygen use usually declineCurrentIncludes nocturnal O2 for COPD in many guides.
    Mobility/ADLsWheelchair, ADL assistance, home health, or nursing facility → often declineCurrentLevel of assistance matters.
    Cancer (active/recent)Active treatment or recent diagnosis often decline2–5 yearsIn remission beyond window may be OK.
    Cardiac eventsRecent MI, stent/bypass, heart failure exacerbation → decline/postpone6–24 mothsStable CAD with meds may pass.
    CHF (heart failure)Symptomatic or recent hospitalization → usually decline2 yearsControlled, no recent events may pass with some carriers.
    Stroke/TIARecent stroke/TIA → decline/postpone2 yearsOlder events with full recovery may pass.
    DiabetesInsulin + complications (neuropathy, retinopathy) → decline with many carriers2 yearsOral meds and A1c control may pass.
    CKD/ESRDDialysis/ESRD → usually declineCurrentEarlier CKD stages vary by carrier.
    Dementia/Alzheimer’sUsually declineCurrentCognitive screens may be used.
    Substance abuseActive alcohol/drug abuse → decline2 years (sustained recovery)Documentation of recovery may help.
    Mental healthSevere, unstable, or recent psych hospitalization → decline/postpone1–2 yearsStable, well-managed often OK.
    Sleep apneaUntreated, severe → postpone/declineCurrentTreated with CPAP and compliant often OK.
    Auto-declines (varies)Organ transplant, metastatic cancer, ALS, schizophrenia (varies) → often declineCarrier-specific.
    State exceptionsSome states have birthday/anniversary rules or continuous accessEases switching without underwriting.
    Rate classes/discountsHousehold/EFT discounts; tobacco surcharge; gender in some statesCurrentCommunity/issue/attained-age rating affects price.

    Important: Rules differ by carrier and state (and by plan letter). Guaranteed Issue or Open Enrollment generally overrides underwriting. If you tell me your state, age, tobacco status, and key conditions, I can summarize likely carriers that are more lenient and where you may qualify.

    Medicare Supplement Trial-Right

    • What it is: A one-time 12-month trial letting you try a Medicare Advantage (MA) plan and still return to Original Medicare with a Medigap policy without medical underwriting.
    • Who qualifies: 1. You joined an MA plan when first eligible at 65 (no prior Medigap), or
      1. 2. You dropped a Medigap policy to try an MA plan for the first time.
    • Your rightsIf you dropped Medigap, you can get the same plan (or a comparable one) from the same insurer, GI.
      • If you never had Medigap, you can buy certain plans (A, B, D, G, K, L; C/F only if Medicare-eligible before 1/1/2020)—state rules vary.
    • Timing: You must switch back and apply within 63 days after your MA coverage ends (keep all notices as proof).
    • Tip: Act early within the 12-month window to avoid gaps and ensure carrier availability.

    Frequently Asked Questions (FAQs)

    Group Health Insurance

    Yes if you have certain disabilities, End-Stage Renal Disease (ESRD), or ALS (special rules apply).

    Yes, generally after the first units each calendar year (who pays first can depend on whether the provider gets free blood).

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