Newsroom · Sioux Falls

Medicare Open Enrollment Period in Sioux Falls 2026: Your Jan 1–Mar 31 Second-Chance Window

Locked into the wrong Medicare Advantage plan after AEP? You have until March 31 to make one more move — and it costs nothing to switch.

Big Sioux Benefits Data Desk

Published July 2, 2026 · 9 min read · Sourced from CMS.gov

If you enrolled in a Medicare Advantage plan during last fall's Annual Enrollment Period and something isn't right — your doctor isn't in-network, your drug is on a higher formulary tier, or the deductible is higher than you expected — the Medicare Open Enrollment Period (OEP) gives you one more window to fix it. It runs January 1 through March 31, and for Sioux Falls' 39,532 Medicare beneficiaries in Minnehaha County, it's a genuinely useful second-chance door that most people don't know exists.

Every figure below comes from public federal data: the CMS PY2026 plan landscape, 2026 CMS star ratings, CMS Hospital Compare, and CDC PLACES 2023. No invented numbers.

What is the OEP — and how does it differ from AEP?

The Medicare landscape has several enrollment windows, and each one works differently. Most people know the Annual Enrollment Period (AEP), but the OEP is the one that matters once you're already on Medicare Advantage and need to change course.

Source: CMS Medicare enrollment period rules; CMS Medicare Advantage & Part D Star Ratings (2026) (5-star SEP eligibility, Minnehaha County 2026).

The key distinction: the OEP is a current MA enrollee-only window. If you are on Original Medicare as of January 1, the OEP doesn't apply to you — you'll need the next AEP (Oct 15–Dec 7) or a qualifying Special Enrollment Period to join Medicare Advantage. The OEP is not a free-for-all; it's a single-use correction tool for people who are already in an Advantage plan.

When your new coverage takes effect

Timing matters in the OEP. A switch made in March takes effect April 1 — meaning you carry your current plan's cost-sharing through March. If you know you need to switch, January is the month to do it.

Source: CMS Medicare enrollment period rules (42 CFR §422.68).

One practical implication: if you have a major procedure or prescription fill planned for early in the year, your current plan's deductible clock has already started. Switching mid-deductible period means your new plan's deductible restarts — factor that into your timing decision.

The 5 Sioux Falls PPOs you might be switching into

All five standard Medicare Advantage PPOs in Minnehaha County are open to any Medicare beneficiary in the county during the OEP. Here's the full 2026 picture:

Source: CMS Medicare Advantage / Part D Landscape (PY2026) & CMS Medicare Advantage & Part D Star Ratings (2026), Minnehaha County, SD.

A few things jump out of this table for OEP switchers:

• Premium isn't the switch trigger. Two plans are at $0 premium, two others are under $70. Nobody should be switching on the monthly premium alone — the differences aren't large enough to justify a network change by themselves.
• The drug deductible is the biggest variable. Aetna's $615 deductible (the 2026 max) vs. Sanford's Align ChoicePlus at $350 or ChoiceElite at $300 is a real difference if you take prescriptions early in the year.
• All five plans share the same 3.5★ CMS rating, so star ratings don't differentiate the choice here. The Minnehaha County OEP decision turns on network and drug formulary, not stars.

The 2026 premium landscape at a glance

Here's how the five plans stack up on the premium axis:

Source: CMS Medicare Advantage / Part D Landscape (PY2026), Minnehaha County 2026.

The real reason people switch: the Sanford-vs-Avera fork

In Sioux Falls, the single most common reason a plan choice goes wrong isn't the premium or even the drug deductible — it's the hospital network. The city runs on two competing health systems, and your plan's preferred network quietly decides which one you access at the lowest cost:

Source: CMS Hospital Compare — Overall Star Ratings.

Sanford USD Medical Center holds a 5-star CMS hospital rating; Avera McKennan carries a strong 4-star. Both are high-quality options — but the split matters for plan choice because Sanford runs its own Medicare plans (the Align ChoicePlus and ChoiceElite PPOs). If you enrolled in an Align plan expecting to use your Avera primary care physician, you may find out-of-network cost-sharing applies. That's a textbook OEP trigger.

The OEP fix: switch to a plan whose preferred network actually matches your doctors. PPO plans do cover out-of-network providers, but at a higher cost-share — and for routine primary care you'll see every quarter, that adds up fast.

What the local health profile means for an OEP switch

Minnehaha County's chronic-condition picture from CDC PLACES 2023 is the lens that makes network and formulary decisions concrete:

Source: CDC PLACES: Local Data for Better Health, County 2023 (2023), Minnehaha County adults.

With 31.7% of county adults managing high blood pressure and 10% living with diabetes, the plans we work with in this area frequently serve members who take three or more daily medications. For those members, the drug deductible difference between a $615 plan and a $300 plan is money spent in January before the cap kicks in. If your current plan's formulary placed a maintenance drug on a higher tier than expected — a common AEP surprise — that's a compelling OEP switch argument.

The Part D angle: what switching means for your drug costs

Every Medicare Advantage plan with drug coverage (MA-PD) in Minnehaha County is subject to the same 2026 federal cost rails: the annual out-of-pocket cap is $2,100 and the maximum standard drug deductible is $615. But "same ceiling" doesn't mean "same path to the ceiling."

When you switch during the OEP, two things reset:

• Your deductible clock restarts. If you've been paying toward your current plan's deductible since January 1, that money doesn't transfer. Your new plan starts you at $0 toward its deductible on the switch effective date.
• Your formulary changes. The tier your prescriptions sit on — which drives your copays until the cap — is plan-specific. A drug that costs $10/fill on one plan might cost $45/fill on another. Pull the new plan's 2026 formulary and run your actual drug list before you switch.

The $2,100 annual cap is a genuine protection no matter which plan you're on, but the cost-sharing landscape between $0 and $2,100 is where the real differences live. If your current plan's formulary tier structure is costing you more than expected, and a different plan tiers your drugs lower, an OEP switch can recoup that difference even after accounting for the deductible restart.

What you cannot do during the OEP — the common misconceptions

The OEP is useful, but it's not unlimited. Knowing what's off the table avoids surprises:

• You cannot join Medicare Advantage for the first time. The OEP is for current MA enrollees only. If you're on Original Medicare as of January 1, you'll wait for the next AEP.
• You cannot use the OEP to change a stand-alone Part D drug plan without also changing your Medicare Advantage plan. Stand-alone PDPs have their own election periods.
• You cannot add or change Medigap coverage through the OEP. Medigap operates under different state-level rules and — outside your guaranteed-issue turning-65 window — typically requires underwriting in South Dakota.
• You cannot make a second OEP switch. You get one move during the January 1–March 31 window, full stop.

What to watch for the rest of 2026

1. Confirm your doctors are in-network before the March 31 OEP deadline. Call the plan's member services or use Medicare's Plan Finder to verify 2026 provider participation — directories lag.
2. Run your drug list against the new plan's formulary. Pay attention to tier placement and whether any of your drugs require prior authorization under the new plan.
3. Factor in the deductible reset. If you've already met part of your current plan's deductible, switching in February or March means a fresh start — time that against any early-year fills.
4. Watch for your Annual Notice of Change (ANOC) next September. OEP fixes last one year; your real annual review happens during AEP Oct 15–Dec 7, when plan changes take effect January 1.
5. Mark your one-switch limit. If you're unsure, wait and compare carefully — you only get one OEP election per calendar year. If you switch in January and find the new plan is also wrong, you'll need a Special Enrollment Period to change again before AEP.

How we know all this: Big Sioux Benefits runs every article through a data desk that cross-references the CMS plan landscape, 2026 star ratings, CMS Hospital Compare, and CDC PLACES local health data — built by Strategic AI Architects. Every figure here is from a public federal dataset. This is education, not advice; confirm your plan, costs, and eligibility with a licensed agent or Medicare.gov. We take no payment from any carrier to feature a plan.