Medicare & Medigap Basics
What is the difference between Medicare Advantage and Medigap?
Last reviewed: · Big Sioux Benefits Data Desk
Medicare Advantage replaces how you receive Medicare (a private plan that bundles Part A, Part B, and usually drug coverage, with its own provider network and an annual out-of-pocket maximum), while Medigap supplements Original Medicare, paying Medicare's own deductibles and coinsurance so you can see any provider in the country that accepts Medicare. You cannot use both at once: it is illegal for anyone to sell you a Medigap policy while you are in a Medicare Advantage plan (source: Medicare.gov).
The qualifier: neither is "better." Medicare Advantage usually costs less per month (many plans charge $0 beyond your Part B premium) and adds extras like dental and vision, but confines you to a network and exposes you to copays up to its out-of-pocket cap. Medigap costs more per month, needs a separate Part D drug plan, and covers no extras, but it makes costs predictable and keeps every Medicare provider open to you, which matters if you travel or split care between systems.
Side by side
| Medicare Advantage (Part C) | Original Medicare + Medigap | |
|---|---|---|
| How it works | Private plan replaces how you receive Parts A/B | Original Medicare pays first; Medigap fills its gaps |
| Providers | Plan network (HMO/PPO); out-of-network costs more or isn't covered | Any provider in the U.S. that accepts Medicare |
| Drug coverage | Usually built in | Separate standalone Part D plan |
| Monthly cost | Often low or $0 plan premium (plus Part B) | Medigap premium + Part D premium (plus Part B) |
| Cost when you use care | Copays/coinsurance up to the plan's annual out-of-pocket max | Little to none with Plan G, beyond the $283 Part B deductible (2026) |
| Switching later | Every year during enrollment periods | Back into Medigap later can require health underwriting in South Dakota |
The South Dakota wrinkle: most beneficiaries here still use Original Medicare. Statewide only about a quarter are in Medicare Advantage or other non-Original coverage, several counties sell no standard MA plan at all, and Medicare Cost plans (a hybrid) remain common. Your county's actual lineup is on its county guide, and the state-rule side of Medigap is in our South Dakota Medigap guide.
Sources
- Medicare.gov — Compare Medigap plan benefits — accessed 2026-08-18
- Medicare.gov — When can I buy Medigap? — accessed 2026-08-18
- CMS — 2026 Medicare Parts A & B Premiums and Deductibles — November 14, 2025; accessed 2026-08-18
Related questions
Can you have Medicare Advantage and Medigap at the same time?
No. Medigap only works alongside Original Medicare, and it is illegal for someone to sell you a Medigap policy while you are enrolled in a Medicare Advantage plan (Medicare.gov). You choose one route or the other, and can change routes only during enrollment windows, with Medigap underwriting possible in South Dakota.
Which is cheaper, Medicare Advantage or Medigap?
Per month, Medicare Advantage is usually cheaper: many plans charge $0 beyond the Part B premium. Over a year of heavy care, Medigap Plan G can be cheaper because it caps your exposure at almost nothing beyond the Part B deductible, while Advantage plans charge copays up to an annual out-of-pocket maximum that CMS lets run into thousands of dollars.
Talking it through beats guessing: book a free, no-pressure conversation, see the South Dakota Medigap guide, or browse all answers.
Big Sioux Benefits is a licensed insurance agency, not affiliated with or endorsed by the U.S. government or the federal Medicare program. We do not offer every plan available in your area. Contact Medicare.gov, 1-800-MEDICARE, or SHIINE (South Dakota's SHIP) for all of your options.