What Is a Medicare Supplement?
Understand the relationship among Original Medicare, Medigap, and Part D.
A secondary private policy
Medigap is supplemental insurance for a person using Original Medicare. After Medicare decides payment on an eligible Part A or B service, the standardized lettered Medigap policy can pay part of the member’s remaining covered cost. It is not Medicare Part C, a substitute for both A and B, or a second way to use an Advantage plan.
Official source: Medicare: How Medigap works ↗ · Medicare: Medigap coverage ↗
The letter fixes core benefits
In most states a given plan letter has the same core benefit schedule at every company, though companies can charge different premiums. For example, Plan B adds the Part A deductible to Plan A’s core benefits; Plan G differs from F mainly in the Part B deductible. Plan K and L pay partial shares of several benefits until their own annual thresholds. Verify each line in Medicare’s chart.
Official source: Medicare: Medigap plan benefits ↗ · Medicare & You 2027, Medigap section (2026 chart) ↗
Prescription drugs are separate
Policies sold after 2005 do not include prescription drug coverage. A person who needs Part D generally considers a separate Medicare drug plan with Medigap and Original Medicare. Formulary, pharmacy, premium and 2026 covered-drug cap follow that drug plan’s terms, not the Medigap letter. Do not mistake Medigap Plan D for Medicare Part D.
Official source: Medicare: How Medigap works ↗ · Medicare: What drug plans cover ↗ · Medicare: 2026 drug cap and payment option ↗
Purchase rights matter
The six-month federal Medigap open-enrollment period begins when a person is at least 65 and has Part B. Afterward, a carrier may apply medical underwriting unless a guaranteed-issue right or stronger state rule applies. Buying a Medigap policy before cancelling other protection can prevent a coverage gap; verify effective dates and preserve notices showing any protected purchase right.
Official source: Medicare: Buying Medigap ↗ · Medicare: Changing a Medigap policy ↗
Price the same letter against itself
Once a letter is chosen, compare multiple carriers on the same plan letter, effective date, age, residence and household discount facts. Medicare notes that a company’s pricing method and discounts can change long-run cost. A cheaper first-month premium is not proof the policy will remain cheaper. Confirm the licensed insurer and obtain the actual rate and policy terms.
Official source: Medicare: Medigap costs ↗ · Medicare: Medigap plan benefits ↗