Newsroom · Sioux Falls

Your Doctor Left Your Medicare Advantage Network: What Sioux Falls Beneficiaries Can Do in 2026

The letter says your doctor is "no longer participating." It doesn't say what that means for the appointment you already have on the calendar — or whether you're stuck with this plan until January.

Big Sioux Benefits Data Desk

Published August 6, 2026 · 17 min read · Sourced from eCFR, CMS.gov, and KFF

If a letter just told you your doctor is leaving your Medicare Advantage plan's network, the short answer is this: your plan owes you advance notice, an active course of treatment gets a minimum 90-day protection, and a full plan switch depends on whether CMS has classified the change as "significant" — which is a narrower bar than most people assume. This guide walks through exactly what federal rule requires at each step, the specific special enrollment period that already exists (and the broader one CMS considered and didn't adopt), why this risk runs higher in a two-hospital-system market like Sioux Falls, and what to actually do this week if you're holding that letter right now.

Every figure and rule below traces to a source fetched directly for this article — the federal regulations governing provider termination notice, continuity of care, and the significant-network-change special enrollment period, KFF's Medicare Advantage network-breadth analysis, the American Hospital Association's summary of CMS's CY2027 final rule, and CMS's 2026 Medicare Parts A & B premiums and deductibles fact sheet. The Sioux Falls plan data comes from the CMS PY2026 Medicare Advantage & Part D Landscape. No invented numbers, and no guessing at what your specific plan will do.

The letter that starts this

It usually looks the same no matter which carrier sent it: a plain envelope, a form letter, a sentence that says a named provider is "no longer participating" in your plan's network as of a specific date. No explanation of why. No mention of the appointment you already have scheduled for six weeks from now. Just a date, and a suggestion to find a new provider using the plan's directory.

That letter is doing exactly what federal law requires it to do — and nothing more. Everything this article covers lives in the gap between what the letter says and what you're actually entitled to, which is considerably more than a form letter usually explains. Two different things can be true about the provider named in that letter: they're leaving the network — the list of doctors and facilities your plan has contracted with — but you may still be inside a protected course of treatment with real rights attached to it. Confusing "not in network anymore" with "not covered anymore" is the single most common and most expensive misunderstanding in this situation.

This guide separates the four things that are actually happening at once: the notice your plan owes you, the treatment protection you may already have, the plan-switch question that depends on a specific federal definition of "significant," and the practical steps to take this week. None of it requires becoming a health policy expert. It requires knowing which of four narrow rules applies to your specific situation.

How much warning your plan owes you

Start with the part that's actually written down in black and white. Federal regulation 42 CFR § 422.111(e) sets two different notice clocks, depending on what kind of provider is leaving:

Source: eCFR — 42 CFR § 422.111(e) (MA organization disclosure requirements, provider termination notice).

Two details matter more than the headline number. First, primary care and behavioral health terminations require the plan to attempt telephonic notice on top of the written letter — a phone call, not just an envelope. Second, and this trips people up constantly: the plan is only required to notify enrollees who are actually connected to that specific provider. If you were never assigned to or seen by the departing doctor, you may never get a letter at all, even if that provider was in your plan's network the whole time you were enrolled. The absence of a notice doesn't mean nothing changed — it may just mean the rule didn't require telling you.

The 90-day rule that protects active treatment

This is the protection most beneficiaries have never heard of, and it's the one that matters most if you're mid-treatment when the letter arrives. Federal regulation 42 CFR § 422.112(b)(8)(i)(B) requires a minimum 90-day transition period for an active course of treatment already underway when the termination or plan switch happens. During that window, your plan not required for that same course of treatment for that same course of treatment, even though the provider is now technically outside the network.

In plain terms: if you started chemotherapy, a course of physical therapy, post-surgical follow-up, or management of a complex chronic condition with that provider before the termination date, the plan cannot cut that treatment off mid-stream or force a new prior authorization fight over it. What the rule does not do is turn that provider into a permanent in-network option for anything unrelated — a new complaint, a routine annual visit, a different condition. The protection follows the treatment already underway, not the relationship generally.

A worked example makes this concrete. Say you're six weeks into a 12-week course of physical therapy for a hip replacement recovery, and your PT clinic's termination letter arrives with an effective date two weeks out. Under the 90-day rule, your plan must continue covering the remainder of that specific course of PT at your normal in-network cost-sharing, without requiring a new prior authorization, for at least 90 days from when the transition period begins — enough to finish the program you're already in. What it doesn't cover: a brand-new referral to that same clinic next year for an unrelated shoulder issue. That's a fresh, out-of-network relationship at that point.

Can you actually switch plans over this?

This is where most of the confusion — and most of the trade-press headlines about being "locked in until January" — actually comes from. There is a special enrollment period tied to network changes. It's just narrower than the phrase "my doctor left the network" suggests. Federal regulation 42 CFR § 422.62(b)(23) has existed since 2014, and it works like this:

Source: eCFR — 42 CFR § 422.62(b)(23) (special enrollment period for a significant change in provider network).

Three conditions decide whether this applies to you, and all three have to line up:

One specialist quietly dropping out of a 40-provider network rarely clears CMS's "significant" bar. A hospital system or a large physician group leaving usually does. The gap between those two scenarios is exactly where most beneficiaries land — and exactly where the frustration comes from.

Here's the part worth sitting with: CMS, not your plan and not you, decides whether a given change counts as "significant based on the affect or potential to affect current plan enrollees." Your plan has to notify you either way if you're connected to that specific provider — but that notice doesn't automatically mean CMS has classified the change as significant enough to trigger a SEP. If your plan's member services line can't tell you clearly whether CMS made that determination for your situation, ask them to check and call you back, or contact Medicare.gov or SHIINE directly to confirm.

The broader fix CMS considered — and didn't make

If you've seen headlines this year about being "locked in" after a provider leaves, they're describing a real and recent policy fight. CMS proposed, as part of its Contract Year 2027 rulemaking, a broader special enrollment period for provider terminations — one that would have dropped the "significant change" threshold entirely and let any beneficiary switch plans whenever any one of their own providers left the network, regardless of how large or small the overall change was.

In its final rule, released April 2, 2026, CMS declined to finalize that broader SEP. The American Hospital Association's summary is direct about it: "CMS declined to finalize a proposal to establish a special enrollment period for provider terminations but will consider whether to engage in future rulemaking."

How common this really is

A single letter can feel like bad luck. The data says it's closer to a structural feature of how Medicare Advantage networks are built. KFF's analysis of Medicare Advantage provider directories found that enrollees, on average, had access to just under half — 48% — of the physicians available to a traditional Medicare beneficiary in the same area. The narrowest networks go further: 1 in 5 enrollees were in plans with 32% or fewer of those physicians in-network.

Source: KFF — Medicare Advantage Provider Networks Limit Enrollees to About Half of the Physicians Available in Traditional Medicare, on Average, published October 27, 2025, analyzing 4,200 Medicare Advantage plans covering roughly 20.3 million enrollees.

One honest caveat worth stating plainly, because the sourcing standard this article follows doesn't allow rounding it away: KFF's provider-directory analysis is based on 2022 data, published in late 2025. It's the most recent rigorous national study of its kind, and network breadth doesn't swing wildly year to year, but it isn't a live 2026 snapshot — treat it as a reliable picture of how narrow these networks tend to run structurally, not a number that updates monthly. What it does establish clearly: a provider leaving your specific network isn't a fluke. It's a predictable outcome of how these networks are built and periodically renegotiated.

Why this risk runs higher in Sioux Falls

Nationally, this is a network-breadth story. Locally, it's also a two-system story. Minnehaha County's Medicare landscape runs through two competing hospital systems, and the local CMS hospital ratings show both are serious options, not a clear winner and a fallback:

Source: CMS Hospital Compare — Overall Star Ratings.

Sanford USD Medical Center holds a 5-star CMS rating; Avera McKennan holds 4 stars. Neither system is the obvious fallback for the other. The wrinkle that matters for this article specifically: one of Sioux Falls' 5 standard 2026 Medicare Advantage PPOs — Sanford's Align plan family — is built and run by one of those two systems. That's not a criticism of the plan; it's a structural fact worth knowing, because it means a network question here is rarely just "is my doctor covered." It's closer to "which system is my doctor part of, and does this specific plan's network lean toward that system or the other one." A provider changing which system they practice under, a group's contract with a specific plan lapsing, or a plan renegotiating its Sanford or Avera terms for the next contract year can all produce the exact letter this article started with — and in a two-system market, the odds of your doctor sitting on the "wrong" side of a renegotiation are real, not hypothetical. (We cover the broader Sanford-vs-Avera plan choice, made at enrollment rather than mid-year, in our Sanford vs. Avera network guide.)

Grievance, appeal, or SEP request — which one you need

Beneficiaries who call their plan or SHIINE about a network termination often ask for the wrong thing simply because the vocabulary is unfamiliar. These are three distinct processes, and using the right name gets you to the right department faster:

• A grievance is a complaint about service or process — for example, that your plan didn't give proper notice under the 45/30-day rule, or wouldn't confirm your continuity-of-care status when you asked directly.
• An appeal challenges a specific coverage decision — most commonly, a denied claim for a visit you already had with the departed provider after the termination date, or a denied continuity-of-care request.
• A special enrollment period request is neither of those. It's an application to switch plans entirely, evaluated against the 42 CFR § 422.62(b)(23) criteria covered above — not a complaint about a specific bill.

If your situation involves a denied claim specifically, the appeals process has its own deadlines and five levels of review, starting with your plan's own reconsideration. We cover that full process, including the current CMS decision deadlines, in our prior authorization and appeals guide. If it's purely about notice or the transition period and no claim has been denied, a grievance filed with your plan — or a call to South Dakota's SHIINE program for free, unbiased help sorting out which process fits — is the more direct route.

What to actually do, in order

None of this requires becoming a health policy expert. It requires reading one letter carefully and making a short list of calls, in this order:

If you're an adult child helping a parent sort through one of these letters, the steps don't change, but consider asking your parent to add you as an authorized representative on their plan account before you make these calls — most member services lines want to speak with the beneficiary directly for anything account-specific, and that one step turns every later call, from a coverage question to a grievance, into something you can actually help with.

How to catch this before it happens again

You can't prevent a plan from renegotiating a contract — that decision happens between the carrier and the provider, well outside your control. What you can do is shrink the odds of being caught off guard by it a second time:

• Read your Annual Notice of Change every fall, not just the year you enrolled. Network composition is one of the sections most people skip — we cover how to read the full document in our ANOC guide.
• Recheck your specific doctors' network status during AEP, even if you're happy with your plan otherwise — a plan directory from a year ago can be stale by October.
• Ask directly whether your doctor is affiliated with Sanford, Avera, or an independent group, and whether that affiliation has changed, since that's the practical driver of most Sioux Falls network shifts.
• If a Medigap-and-Part-D combination fits your budget, weigh it seriously if network continuity matters more to you than the lower premium a Medicare Advantage plan often carries — it removes this entire category of risk structurally, in exchange for a higher monthly cost.

What to watch through AEP 2026

1. Read every page of your ANOC this fall, arriving by September 30 for 2027 coverage — network changes are disclosed there before they show up as a termination letter mid-year.
2. Confirm your specific doctors' 2027 network status directly with the plan, not just by checking whether the plan name sounds the same as last year.
3. If you've had a network termination this year, ask your plan point-blank whether it was ever classified "significant" by CMS — you're entitled to a clear answer, not a runaround.
4. Watch for CMS's promised future rulemaking on a broader provider-termination SEP — the door was left open, not closed, in the CY2027 final rule.
5. If you're weighing Medigap for the first time because of a network scare, remember guaranteed-issue rights are narrower outside your original enrollment window — ask about medical underwriting before you assume the switch is simple.

Big Sioux Benefits compares the plans we offer in the Sioux Falls area against your actual doctors, not just your ZIP code — including which hospital system each plan really favors. That's worth sorting out before a termination letter forces the question, not after.

How we know all this: Big Sioux Benefits runs every article through a data desk that cross-references the federal Code of Federal Regulations governing Medicare Advantage (42 CFR Part 422), CMS's own 2026 cost fact sheets, KFF's Medicare Advantage network-breadth research, the American Hospital Association's regulatory summaries, and the CMS PY2026 Minnehaha County plan landscape — built by Strategic AI Architects. Every figure here is from a public federal or nonprofit source fetched directly for this article, with the data year stated wherever it isn't the current plan year. This is education, not legal or insurance advice; your specific plan's Evidence of Coverage and CMS's determination govern your actual situation, and we take no payment from any carrier to feature a plan.