A Medicare Supplement — also called Medigap — sits alongside Original Medicare and pays toward costs Original Medicare leaves behind. It is not a replacement for Medicare and it is not the same thing as Medicare Advantage.

The problem it solves

Original Medicare pays most of your Part B costs but leaves you roughly 20% of each service, with no annual cap. A Supplement covers much of that, which converts an open-ended exposure into a predictable monthly premium. That predictability is the whole proposition.

Standardisation, and what it means for shopping

Medigap plans are standardised by letter. The basic benefits of a given plan letter are the same from one insurer to the next — a Plan G is a Plan G. What differs between companies is the premium, the underwriting, available discounts, and how the company behaves when you need it.

That makes this one of the few insurance purchases where comparing on price is actually reasonable, because the product itself is genuinely identical. It is also why a licensed agent who can see several insurers is useful here.

Timing is the critical part

Your Medigap Open Enrollment Period is the six months starting the first month you are 65 and enrolled in Part B. During that window you cannot be turned down or charged more for health reasons. Outside it, Supplements are generally medically underwritten in South Carolina, and a health condition can mean a higher price or a refusal.

This is the single most consequential deadline in Medicare and it does not repeat. If you are approaching 65, do not let it pass unexamined.

Under 65 in South Carolina

This is where South Carolina differs from its neighbours. Federal law does not require insurers to sell Medigap to people under 65, and South Carolina law does not require it either — access runs through the state pool. North Carolina guarantees Plan A plus D or G; Tennessee requires the same plans sold at 65 to be offered under 65.

If your Medicare came from a disability, read Medicare before 65 on disability in South Carolina before assuming a Supplement is on the table.

Supplement or Advantage

They are different structures, not better and worse. A Supplement does not route you through a network; a Medicare Advantage plan caps your in-network spending and often bundles drug coverage. See how Medicare Advantage works in South Carolina and weigh both.