Medicare Supplement (Medigap) Claim Denied? What Seniors Can Do

Medicare supplement insurance — commonly called Medigap — is designed to fill the cost-sharing gaps in Original Medicare. Seniors pay monthly premiums for these policies with the expectation that covered services will be paid. When a Medigap claim is denied, it is often unexpected and financially significant.

The good news: Medigap plans are standardized by federal law, which means the rules are clearer than in many other insurance disputes. Here's what you need to know.

How Medigap Works

Medigap policies supplement Original Medicare (Parts A and B). They do not cover Medicare Advantage (Part C) or Medicare Part D drug plans. Key features:

• Medigap plans are sold by private insurers but regulated by CMS and state insurance departments
• Plans are identified by standardized letter designations (Plan G, Plan N, etc.) — coverage for the same letter plan is identical regardless of insurer
• Medigap generally pays after Medicare, covering deductibles, copays, coinsurance, and sometimes excess charges
• Most Medigap plans do not have Prior Authorization Denied: How to Appeal" class="auto-link">prior authorization requirements for services already covered by Medicare

Common Medigap Claim Denial Scenarios

Medicare Denied First

The most common reason Medigap denies a claim: Original Medicare denied it first, and the Medigap plan follows Medicare's determination. In this case, the fight begins with Medicare, not the Medigap insurer. Medicare denial appeals go through the CMS appeals process.

Service Not Covered by Medicare

Medigap only covers what Medicare covers. If a service is excluded from Medicare — routine dental, vision, hearing aids, most long-term care — Medigap does not cover it either. However, some Medigap plans offer limited coverage for these services as rider benefits. Check your specific policy.

Assignment Issues

Some Medigap plans only pay "Medicare Assignment" amounts. If your provider does not accept Medicare assignment and charges excess fees (up to 15% above Medicare rates), Plan G covers Medicare Part B excess charges, but not all plans do. Check your plan letter for excess charge coverage.

Coordination of Benefits Errors

If you have both Medigap and employer retiree coverage or other insurance, claims can be misrouted. Ensure the billing sequence is correct: Medicare pays first, then Medigap, then any other secondary payer.

Guaranteed Issue Rights

One of the most important Medigap protections is the guaranteed issue right — the right to buy a Medigap policy without medical underwriting in certain situations:

• Your Medicare Advantage plan leaves the service area or stops offering the plan
• You move out of your Medicare Advantage plan's service area
• You enrolled in Medicare Advantage at age 65 and within one year want to switch to Original Medicare + Medigap
• You are enrolled in a Medicare SELECT policy and the hospital closes or no longer participates

During guaranteed issue periods, insurers cannot deny coverage or charge more based on your health. If a Medigap insurer denied your application or charged more during a guaranteed issue period, file a complaint with your state insurance department immediately.

Open Enrollment vs. Underwriting Periods

The six-month Medigap open enrollment period begins when you are both age 65 or older and enrolled in Medicare Part B. During this window, insurers cannot use health underwriting to deny, price-up, or limit your coverage. After this window, many states allow insurers to underwrite — which can result in denials or higher premiums for those with pre-existing conditions.

State variation: Some states — including California, Connecticut, Maine, Massachusetts, Minnesota, New York, and Washington — provide continuous or birthday rule open enrollment for Medigap, giving seniors additional protected periods to enroll or switch plans without underwriting. If you were denied Medigap outside the standard open enrollment period, check your state's rules.

How to Appeal a Medigap Claim Denial

Step 1: Determine Whether the Issue is Medicare or Medigap

Request your Medicare Summary Notice (MSN) and your Medigap EOB)" class="auto-link">Explanation of Benefits (EOB). If Medicare denied the claim, your appeal is with Medicare. If Medicare paid but Medigap did not follow, your appeal is with the Medigap insurer.

Step 2: File a Formal Written Appeal with the Medigap Insurer

Send a letter requesting reconsideration of the denial, including the Medicare EOB showing what Medicare paid, your Medigap policy number, and the specific denial reason you are disputing.

Step 3: Contact Your State Insurance Department

State insurance departments regulate Medigap plans. File a complaint if the insurer is not following the standardized coverage rules or is improperly denying claims.

Step 4: Contact Your State Health Insurance Assistance Program (SHIP)

Every state has a SHIP program offering free, unbiased Medicare counseling. SHIP counselors can help you understand your Medigap rights, identify errors, and assist with appeals.

Step 5: Escalate to CMS

For systemic Medigap issues, complaints can be filed with CMS through Medicare.gov.

Fight Back With ClaimBack

Medigap denials affect seniors on fixed incomes who counted on their supplemental coverage. ClaimBack helps you draft formal appeal letters, identify whether the denial violates standardized plan rules, and navigate the state and federal complaint processes.

Start your Medigap appeal at ClaimBack

Related Reading

• How to Write an Insurance Appeal Letter
• Internal vs. External Insurance Appeal: What's the Difference?
• Common Reasons Insurance Claims Are Denied