What a Medicare Supplement actually does
Original Medicare pays first for covered services. Then the Medigap policy can help pay the share you owe under that policy, such as certain deductibles, copays, or coinsurance. That is the whole point of the word supplement. It does not replace Medicare. It sits behind Medicare and helps with some of the gaps.
You need Original Medicare first
Medicare.gov explains that you generally must have Original Medicare, meaning Part A and Part B, before buying a Medigap policy. This is why the supplement conversation should not start in isolation. First confirm Medicare eligibility and Part B timing. Then compare whether a supplement fits the coverage path you want.
Plan letters are standardized, but prices are not
In most states, Medigap plan letters are standardized. A Plan G from one company has the same basic benefits as a Plan G from another company. The premium can still be very different. Pricing method, rate history, household discounts, tobacco status, age, company practices, and state rules can all matter. Massachusetts, Minnesota, and Wisconsin standardize Medigap differently.
Plan G, Plan N, and Plan F get most of the attention
Many shoppers compare Plan G and Plan N because they are common choices for people new to Medicare today. Plan F is different because Plans C and F are generally not available to people who became newly eligible for Medicare on or after January 1, 2020. A lower premium can be attractive, but the better question is whether the plan's cost sharing and long-term premium pattern fit the person.
Prescription drug coverage is separate
Medigap policies sold after 2005 do not include outpatient prescription drug coverage. If you want drug coverage, you usually compare a stand-alone Part D plan. That means a real supplement budget includes the Part B premium, the Medigap premium, the Part D premium, and the expected drug costs.
The 6-month Medigap window matters
The federal Medigap Open Enrollment Period starts the first month you are 65 or older and enrolled in Part B. It lasts 6 months. During that window, an insurance company cannot deny you a Medigap policy it sells because of pre-existing health problems. After that one-time window, you may have fewer options, may pay more, or may face medical underwriting unless a guaranteed-issue right or state-specific protection applies.
One policy covers one person
A Medigap policy covers one person. If both spouses want supplement coverage, each spouse buys a separate policy. The right plan letter and company can also differ between spouses because age, tobacco status, budget, health history, prescriptions, and travel habits may not match.
Medigap and Medicare Advantage do not stack
A Medigap policy is different from a Medicare Advantage plan. You cannot use Medigap to pay Medicare Advantage copays, deductibles, or premiums. When someone is comparing these two paths, the decision is usually whether they want Original Medicare with add-ons or a Medicare Advantage plan. Trying to carry both as if they work together is where confusion starts.
How to decide whether a supplement fits
A supplement can fit people who value Original Medicare, provider flexibility, and more predictable cost sharing. It may be less attractive for someone who wants a lower monthly premium, wants extra benefits bundled into one plan, or is comfortable with Medicare Advantage networks and plan rules. The honest comparison includes doctors, prescriptions, travel, budget, underwriting, and the long-term premium.