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Medigap shopping comes with its own vocabulary, and misunderstanding even one term—like the difference between “guaranteed issue” and “open enrollment”—can lead to a costly mistake. This glossary defines every essential Medigap and Medicare Supplement term in plain English, organized alphabetically for quick reference.
A
Attained-Age Rating: A Medigap pricing method where premiums start lower but increase as you age, unlike community-rated or issue-age-rated policies. See our state cost guide for how this affects long-term pricing.
C
Community Rating: A Medigap pricing method where every policyholder pays the same premium regardless of age, common in certain states.
Coinsurance: The percentage of a medical bill you’re responsible for after Medicare pays its share—typically 20% under Part B for Original Medicare alone.
Copayment (Copay): A fixed dollar amount you pay for a covered service, used by Medigap Plan N for doctor and ER visits.
Creditable Coverage: Prior health coverage (such as an employer plan) that can reduce or eliminate a Medigap pre-existing condition waiting period if there’s minimal gap before applying.
F
Foreign Travel Emergency Coverage: A Medigap benefit (included in Plans C, D, F, G, M, and N) that covers 80% of emergency care costs incurred outside the U.S., subject to a deductible and lifetime limit.
Free Look Period: A 30-day window that allows you to hold both an old and new Medigap policy simultaneously when switching, so you can cancel the new one and keep the old if it isn’t a good fit. See Switching Medigap Plans.
G
Guaranteed Issue Right: A legal protection that forces an insurer to sell you a Medigap policy regardless of health history, typically triggered by losing other coverage through no fault of your own. Full list in Guaranteed Issue Rights for Medigap.
H
High-Deductible Plan GA version of Plan G with a lower monthly premium in exchange for paying a set annual deductible before the plan’s benefits begin.
I
Issue-Age Rating: A Medigap pricing method where your premium is based on your age when you first bought the policy and does not increase simply because you get older.
L
Look-Back Period: The 6-month period before your Medigap policy’s effective date during which an insurer can review your medical history to determine if a condition is “pre-existing” for underwriting purposes.
M
Medical Underwriting: The process an insurer uses to evaluate your health history before approving a Medigap application and setting your premium. Full explanation in Medigap Underwriting Explained.
Medicare Advantage (Part C) A private, managed-care alternative to Original Medicare that often includes drug coverage and extra benefits but uses provider networks. See our comparison: Medigap vs. Medicare Advantage.
Medigap, also called Medicare Supplement Insurance—a private policy that helps pay the out-of-pocket costs left over after Original Medicare pays its share.
Medigap Open Enrollment Period A one-time, 6-month window that begins when you’re 65 or older and enrolled in Part B, during which insurers must sell any Medigap policy without underwriting. Full details in Medigap Open Enrollment Period.
O
Original Medicare: The traditional government-run Medicare program, consisting of Part A (hospital insurance) and Part B (medical insurance), which Medigap is designed to supplement.
Out-of-Pocket Maximum The most you’ll pay for covered services in a plan year; used by Medicare Advantage and Medigap Plans K and L, but not applicable to Plans G or N since those cover nearly all costs directly.
P
Part A: The portion of Original Medicare that covers inpatient hospital stays, skilled nursing facility care, hospice, and some home health care.
Part B: The portion of Original Medicare that covers outpatient care, doctor visits, preventive services, and durable medical equipment.
Part B Excess Charge An additional amount (up to 15% above the Medicare-approved rate) that a provider not accepting Medicare assignment can legally charge. Covered by Plan G, not by Plan N. See Plan G vs. Plan N.
Part D is Medicare’s optional prescription drug coverage, sold as a standalone plan for Medigap holders since Medigap itself doesn’t cover drugs.
Plan Letter: The standardized designation (A, B, D, G, K, L, M, N, and legacy C/F) that identifies exactly which benefits a Medigap policy covers. Full comparison in Medigap Plan Letters Explained.
Pre-Existing Condition A health issue for which you received medical advice, diagnosis, care, or treatment during the 6 months before your Medigap policy’s effective date.
S
SHIP (State Health Insurance Assistance Program) A free, government-funded counseling service available in every state to help Medicare beneficiaries understand their options, including Medigap.
Skilled Nursing Facility (SNF) Coinsurance The daily coinsurance amount owed after a set number of days in a skilled nursing facility under Original Medicare, covered by most Medigap plans.
Standardized Benefits: The federal requirement that every Medigap policy with the same letter must cover identical core benefits nationwide, regardless of which insurer sells it.
T
Trial Right: A Guaranteed Issue protection allows someone who tries Medicare Advantage for the first time (or drops Medigap to try it) to switch back to Medigap within 12 months without underwriting.
U
Underwritten Policy: A Medigap policy issued after the insurer reviewed the applicant’s health history, potentially resulting in a higher premium, a waiting period, or denial.
W
Waiting Period: A period of up to 6 months during which an underwritten Medigap policy may decline to pay for care related to a pre-existing condition, even though premiums are still due.
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