Medical underwriting is an insurer asking about health before deciding whether to issue a policy and at what price. It has almost no role in Medicare Advantage and a decisive one in Medigap, and that asymmetry is the single most consequential thing in this market that nobody is told at the point of sale.
Where it does not apply
Medicare Advantage plans generally may not screen applicants on health. That is a deliberate feature of the programme: a plan takes who applies during the windows, and the risk is handled through the payment the plan receives rather than through selection. So a person choosing a plan in an enrolment window is not being underwritten and nothing about their health record decides whether they may join.
Where it applies, and when it does not
Medigap is the opposite. Outside protected circumstances an insurer may ask about health, and may decline or price accordingly. The protected circumstances are the point: a one-time open enrolment window running from when a person is first both sixty-five and enrolled in Part B, and a set of guaranteed issue rights triggered by particular events. Inside those, health cannot be used against an applicant; outside them, in most states, it can.
Why the asymmetry makes the first decision heavier
It means the two arrangements are not equally reversible. Moving into a Medicare Advantage plan is easy in a window; moving back and buying a supplement may involve health questions, and health changes with time, which is the direction it usually changes in. A few states have written their own rules to soften this, which is why the honest answer to whether a decision can be undone begins with which state you are in.
Questions people ask about medical underwriting
Does Medicare Advantage use medical underwriting?
Generally no. Plans may not screen applicants on health during the enrolment windows.
When can a Medigap insurer ask about my health?
Outside your one-time Medigap open enrolment window and outside a guaranteed issue right, in most states, subject to whatever your own state has legislated.
Is that the same everywhere?
No. Some states give broader rights than federal law requires, and that is one of the few Medicare questions whose answer genuinely depends on the state.
Where do I check my own state's rule?
Your State Health Insurance Assistance Program and your state insurance department. Both are free and neither is paid on what you choose.