A Medigap policy is a Medicare Supplement medical insurance policy that fills the gaps in

Medicare Drug coverage, also known as Medicare Part D, specifically deals with prescription drug coverage. It is a separate insurance plan that can be added to original Medicare to help cover the costs of prescription medications. Medigap policies do not provide coverage for prescription drugs.

Medicare Advantage plans, also known as Medicare Part C, are an alternative to original Medicare. These plans are offered by private insurance companies approved by Medicare and provide all Part A and Part B coverage, often including additional benefits like vision and dental. Medigap policies do not work with Medicare Advantage plans.

There is no specific "Medicare C" plan. Medicare Part C refers to Medicare Advantage plans, which are comprehensive health plans offered by private insurers. Medigap policies are not designed to work with Medicare Advantage plans but are meant to supplement original Medicare (Parts A and B).