If you have Original Medicare, you may have noticed it does not cover everything, leaving you with copays, coinsurance, and deductibles. Medigap, or Medicare Supplement Insurance, exists to fill those gaps. Here is what Medigap is, how it works, and why the timing of your purchase matters so much. Rules and prices vary, so verify current details before deciding.
What Medigap Is
Medigap is private insurance that supplements Original Medicare (Part A and Part B) by helping pay the out-of-pocket costs Medicare leaves you, such as copayments, coinsurance, and deductibles. You buy it from a private insurer, but the benefits are standardized by the government, so a given plan offers the same core benefits no matter which company sells it. Medigap works alongside Original Medicare, not on its own.
Standardized Plans
Medigap plans are labeled with letters, such as Plan A, B, D, G, K, L, M, and N, and each letter provides a standardized set of benefits. That means a Plan G from one insurer covers the same things as a Plan G from another, so you can compare mainly on price and service. Plan G and Plan N are popular choices for new enrollees. Note that Plans C and F, which covered the Part B deductible, are closed to people who became eligible for Medicare on or after January 1, 2020, though those eligible earlier can still buy them.
Why Timing Matters
This is the most important practical point. The best time to buy Medigap is during your Medigap Open Enrollment Period, a six-month window that starts when you are 65 or older and enrolled in Medicare Part B. During this period you have a guaranteed right to buy any Medigap policy with no medical underwriting, meaning insurers cannot deny you or charge more due to your health. Outside this window, insurers can in most states reject you or raise your price based on health, so buying during open enrollment can save you a great deal.
Important Limits
A few rules are worth knowing. Medigap only works with Original Medicare, not with Medicare Advantage, and it is illegal for someone to sell you a Medigap policy while you are on a Medicare Advantage plan unless you are switching back. Medigap generally covers one person, so a spouse needs their own policy. And Medigap usually does not include prescription drug coverage, which comes separately through a Part D plan.
Choosing a Medigap Plan
To choose well, first decide which standardized plan letter matches the coverage you want, then compare prices among insurers for that same letter, since benefits are identical but premiums are not. Ask how each insurer rates premiums, since some raise prices with age. Consider a separate Part D drug plan for medications. And if possible, buy during your open enrollment period to lock in guaranteed coverage. Comparing the same plan letter across insurers is the key to getting the best value.
Medigap and the Rest of Your Coverage
It helps to see where Medigap fits among your Medicare choices. Many people pair Original Medicare plus a Medigap plan plus a Part D drug plan for broad, predictable coverage, while others choose a Medicare Advantage plan instead, which bundles coverage but uses networks and cannot be combined with Medigap. Neither is universally better; it depends on whether you value flexibility and predictable costs, which Medigap offers, or lower premiums with network rules, which Advantage often offers. Understanding that these are two different paths helps you choose the combination that fits your health needs and budget.
Medigap FAQs
Can I switch Medigap plans later?
You can apply anytime, but outside your open enrollment period insurers can use medical underwriting, so you may be denied or charged more.
Is Medigap the same everywhere?
The standardized benefits by plan letter are the same, but prices vary by insurer and state, so compare the same letter across companies.
Do I still need Part D with Medigap?
Yes, if you want prescription coverage, since Medigap generally does not include drug coverage.
What does Medigap cover?
It helps pay the out-of-pocket costs of Original Medicare, such as copays, coinsurance, and deductibles.
Are Medigap plans standardized?
Yes. Plans are labeled by letter, and a given letter offers the same benefits regardless of the insurer.
When is the best time to buy Medigap?
During your six-month Medigap Open Enrollment Period, when you have guaranteed issue with no medical underwriting.
Can I have Medigap with Medicare Advantage?
No. Medigap only works with Original Medicare, not Medicare Advantage.
Why are Plans C and F restricted?
They covered the Part B deductible and are closed to people who became Medicare-eligible on or after January 1, 2020.
Does Medigap cover prescriptions?
Generally no. Drug coverage comes separately through a Medicare Part D plan.
