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2026 Medicare Advantage in South Dakota: 38 plans, 9 carriers, and why your county decides everything

South Dakota has 38 carriers' plans for 2026 — but where you live decides whether you choose among fourteen of them, or just one.

Medicare ATX Data Desk

Published June 12, 2026 · 11 min read · Sourced from CMS.gov

South Dakota is not a big Medicare Advantage market by national standards — but it is a revealing one. Nine organizations are spread across a state where the over-65 population is concentrated in a handful of counties and thinly scattered everywhere else. That geography produces one of the widest plan-availability gaps in the country: a beneficiary in Brookings chooses among fourteen Medicare Advantage plans, while one in Edmunds County has exactly one. Same Medicare, same year, completely different menu.

We pulled every figure below from the CMS PY2026 Medicare Advantage / Part D landscape files, CMS county enrollment data, the 2026 CMS star ratings, CMS Hospital Compare, and CDC PLACES health data. Here is what South Dakota's 2026 Medicare map actually looks like — and what it means if you live here.

How many plans are there, really?

"38 plans" is the honest statewide number of unique plans, but it bundles together very different products. Here's the breakdown by type — and notice the premiums diverge wildly:

Source: CMS Medicare Advantage Market Statistics (2026), grouped by plan type, South Dakota.

The headline most people miss: 13 of the 38 are true Medicare Advantage PPOs, 11 are stand-alone Part D drug plans, and 8 are Medicare Cost plans — a legacy product (more on that below). Add 4 Dual-Eligible D-SNPs and 2 Institutional I-SNPs and you have the full picture. South Dakota has no HMO Medicare Advantage plans at all in 2026; every MA plan here is a PPO, which matters because PPOs let you go out-of-network (at higher cost) where HMOs generally don't.

The nine carriers behind the plans

Nine organizations compete statewide, but they are nowhere near interchangeable — average premiums range from under $27 to over $80 a month, and county footprints range from 1 to 66.

Source: CMS Medicare Advantage Market Statistics (2026), grouped by parent organization. Three Part-D-only carriers (Humana, Centene, Health Care Service Corp.) complete the nine.

Two things jump out. First, Medica's 12 plans are the most of any carrier — but they're the most expensive, averaging $80.57/month, because most are Medicare Cost plans rather than premium-light Advantage plans. Second, the genuinely low-cost competition is a two-horse race: Aetna/CVS at $26.84 and UnitedHealthcare at $27.67. If you want a $0 or near-$0 Advantage premium in South Dakota, those two plus Sanford's Align plans are where you'll find it.

Where the beneficiaries actually are

Medicare enrollment in South Dakota is concentrated in a handful of counties — which is exactly why carriers cluster there and rural counties get left thin. Here are the largest Medicare markets by CMS enrollment:

Source: CMS Medicare Monthly Enrollment by County (2026).

Minnehaha County alone holds 39,532 Medicare beneficiaries — nearly twice Pennington County (Rapid City) and more than triple Brown County (Aberdeen). Together with neighboring Lincoln County's 12,719, the Sioux Falls metro is the gravitational center of Medicare in South Dakota. That concentration is good news for choice: the more beneficiaries in a county, the more carriers fight for them.

Fourteen plans, or one: the county lottery

This is the single most important fact about Medicare in South Dakota: your menu is set by your county line.

Brookings, Day, and Deuel counties each offer 14 Medicare Advantage plans. The Sioux Falls metro has 11. And in the most rural reaches — Edmunds and McPherson — there is exactly one plan, with Tripp County close behind at two. A neighbor twenty miles across a county line can have a completely different set of options, different premiums, and a different provider network. In a thin market, the few plans available matter even more, because there is far less room for error.

The Medica "Cost plan" wrinkle most of the state misses

South Dakota is genuinely unusual: it still has a thriving Medicare Cost plan market, almost entirely from Medica, across 48 counties. A Cost plan is an older form of private Medicare coverage with one big advantage over Medicare Advantage — you can still use Original Medicare for any care you get outside the plan's network, with no penalty. The trade-off is price. Medica's Cost plans run from about $59 to $335 a month, versus the near-$0 premiums on the cheapest Advantage PPOs.

For a snowbird, a frequent traveler, or someone who wants the freedom of Original Medicare with a drug benefit bolted on, a Cost plan can be worth the premium. For most local, stay-in-network beneficiaries, it usually isn't. The point is simply that "Medicare Advantage in South Dakota" quietly includes a product that behaves very differently — and the brochure won't always make that clear.

The dual-eligible layer: D-SNP and I-SNP

Beyond standard Advantage, South Dakota has two kinds of Special Needs Plans. Four Dual-Eligible D-SNPs (from UnitedHealthcare and Aetna) serve people who have both Medicare and Medicaid, available in 51 of the state's counties. Two Institutional I-SNPs from Sanford's Great Plains serve nursing-home residents. With 122,936 South Dakotans on Medicaid as of February 2026 — in a Medicaid-expansion state — the dual-eligible population these plans serve is substantial. We break the D-SNP options down in detail in our Sioux Falls D-SNP analysis.

Why your health — not just the premium — picks the plan

A $0 premium means nothing if your medication sits on a plan's top drug tier, or your cardiologist is out of network. And South Dakotans carry real chronic-condition load. Here's what CDC data shows among adults in Minnehaha County:

Source: CDC PLACES: Local Data for Better Health, County 2023 (2023, model-based prevalence).

More than three in ten adults have high blood pressure, over a third are obese, and one in ten has diabetes. Each of those is a reason to check a plan's formulary and specialist network before you sign — which is exactly the comparison a good local agent runs for you, free.

Hospitals: the other half of the equation

A Medicare Advantage plan is only as good as the hospitals and doctors in its network. The Sioux Falls area is anchored by two competing health systems, and their CMS quality ratings are strong:

Source: CMS Hospital Compare — Overall Star Ratings.

Because Sanford and Avera are rivals, the health system you use can decide which plan is right for you — and a plan that covers your system this year is not guaranteed to next year. Confirming your hospital and doctors are in a plan's network is the single most important step, especially in rural counties where the nearest in-network hospital might be a 45-minute drive.

What South Dakota beneficiaries should watch for in 2027

1. Rural network and plan exits. In counties with only one or two plans, a single carrier pulling out can erase your option entirely. Watch your fall Annual Notice of Change closely if you live outside the metro.
2. Cost-plan changes. Medicare Cost plans have been shrinking nationally for years. If you're on a Medica Cost plan, confirm it's renewing — and whether an Advantage PPO would cover the same care for far less.
3. Premium creep on $0 plans. The cheapest Advantage PPOs run on thin margins. Expect some $0-premium plans to add a premium or trim dental/vision/hearing extras for 2027.
4. D-SNP integration rules. CMS is tightening the rules around Dual-Eligible plans. If you're a dual, re-check your plan every year rather than letting it auto-renew.
5. The Annual Enrollment Period (Oct 15 – Dec 7). Every figure in this article matters most during AEP, when you can change plans for the coming year. The beneficiaries who compare carefully make better decisions than the ones who renew on autopilot.

How we know all this: Big Sioux Benefits runs every article through a data desk that cross-references the CMS plan landscape, CMS enrollment, 2026 star ratings, hospital quality data, and CDC health data in real time — a very caffeinated research desk that never sleeps, built by Strategic AI Architects. Every figure here comes from publicly available federal datasets. This article is education, not advice; confirm your own plan, costs, and eligibility with a licensed agent. Big Sioux Benefits takes no payment from any carrier to feature a plan.