Medicare & Medigap Basics
Can you switch from Medicare Advantage back to Original Medicare and Medigap?
Last reviewed: · Big Sioux Benefits Data Desk
Yes, you can leave Medicare Advantage and return to Original Medicare during the Annual Enrollment Period (October 15–December 7, effective January 1) or the Medicare Advantage Open Enrollment Period (January 1–March 31, if you're already in an MA plan), but the Medigap half of the move is the catch: in South Dakota an insurer must accept your Medigap application only if a federal guaranteed-issue right applies, most importantly the 12-month "trial right", and otherwise may medically underwrite (source: Medicare.gov).
The qualifier: think of it as two separate transactions. Dropping the Advantage plan is easy and calendar-driven. Getting Medigap afterward is rights-driven, and the rights are narrow. The two trial rights that matter: (1) you joined a Medicare Advantage plan when you were first eligible for Medicare at 65 and leave within 12 months, you can buy any Medigap policy sold in your state; (2) you dropped a Medigap policy to try an Advantage plan for the first time and leave within 12 months, you can get your old policy back if the carrier still sells it, or another specified plan if not (Medicare.gov, guaranteed issue rights).
The mechanics
| Step | Window | Guaranteed? |
|---|---|---|
| Drop MA plan → Original Medicare | Oct 15–Dec 7 (AEP) or Jan 1–Mar 31 (MA-OEP) | Yes, calendar right, no health questions |
| Add a standalone Part D drug plan | Same windows | Yes |
| Buy Medigap, within a 12-month trial right | Generally starts 60 days before coverage ends and runs 63 days after | Yes, the specified plans, no health questions |
| Buy Medigap, no right applies (South Dakota) | Any time | No, underwriting; apply and be approved before dropping the MA plan |
The order of operations is the practical takeaway: if no guaranteed-issue right applies, get the Medigap approval in hand first, then cancel the Advantage plan in an enrollment window, never the reverse, or you can land on Original Medicare with no supplement and no way back until fall. South Dakota adds no state switching window of its own (no birthday rule); the full rules live in our South Dakota Medigap guide, and your county's MA lineup is on its county guide.
Sources
- Medicare.gov — Guaranteed issue rights — accessed 2026-08-18
- Medicare.gov — When can I buy Medigap? — accessed 2026-08-18
- Medicare.gov — Joining, switching, or dropping a Medicare Advantage Plan — accessed 2026-08-18
Related questions
What is the Medicare Advantage 12-month trial right?
A federal guaranteed-issue right: if you joined an MA plan when first eligible at 65 (or dropped a Medigap policy to try MA for the first time) and you leave within 12 months, you can buy a Medigap policy without health questions, any policy in the first case; your old policy back (or a specified substitute) in the second (Medicare.gov).
Can I switch from Medicare Advantage to Medigap during the January–March window?
You can use the January 1–March 31 MA Open Enrollment Period to drop your Advantage plan for Original Medicare and add Part D, but that window guarantees nothing about Medigap. Unless a trial right or other guaranteed-issue event applies, a South Dakota carrier can still underwrite your Medigap application, so secure that approval first.
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.