The news: the St. Louis region's largest hospital system is splitting from two of the country's biggest insurers for Medicare Advantage members. BJC HealthCare and Washington University Medicine will leave the Medicare Advantage networks of Aetna and Anthem Blue Cross Blue Shield on January 1, 2027, officials confirmed on October 20, after contract negotiations failed, the St. Louis Post-Dispatch reports.
Roughly 85,000 Medicare Advantage enrollees are caught in the middle — just over 72,000 Aetna members and about 13,800 Anthem members in the 15-county bi-state St. Louis metro, according to federal data cited by the Post-Dispatch. The 14 hospitals, hundreds of clinics, and thousands of physicians that make up the region's top health system — including Barnes-Jewish Hospital and Siteman Cancer Center — will be out of network for those members starting New Year's Day. The timing is unforgiving: Medicare's Annual Enrollment Period runs October 15 through December 7, 2026 — it is happening right now. Here is what happened, what it means for affected seniors, and exactly what to do before the deadline.
In this guide
What happened: the failed BJC–Aetna and BJC–Anthem negotiations
The split has been brewing for months. BJC and Anthem have been negotiating since February 2026, with BJC telling Missouri employers over the summer that the sides were stuck on three issues: claim denials, prior-authorization requirements, and reimbursement rates that BJC says do not cover rising costs, according to an earlier InsuranceNewsNet report.
Now it is final — at least for Medicare Advantage. Patients have already received letters: Dr. Paul Scheel Jr., chief executive officer of WashU Medicine Physicians, wrote to patients that "beginning January 1, 2027, WashU Medicine will no longer participate in the Aetna Medicare Advantage plan." A similar BJC letter went out a month earlier. BJC spokesperson Laura High confirmed to the Post-Dispatch: "Despite lengthy negotiations, BJC HealthCare was not able to come to a satisfactory agreement with Anthem Medicare Advantage or Aetna Medicare Advantage plans in order to renew these agreements after Dec. 31, 2026."
The scale: 85,000 seniors and the region's top hospitals
The affected population is large because Aetna is the region's second-largest Medicare Advantage carrier: it covers just over 72,000 MA enrollees in the 15-county metro, behind only UnitedHealthcare. Anthem covers about 13,800, nearly all on the Missouri side. Together that is roughly 85,000 seniors who chose their plan partly because BJC was in network.
And the facilities going out of network are not interchangeable community hospitals. They include Barnes-Jewish Hospital (ranked the No. 1 adult hospital in Missouri by U.S. News & World Report), St. Louis Children's Hospital (No. 1 children's hospital in Missouri), Siteman Cancer Center (No. 1 cancer center in Missouri), Missouri Baptist Medical Center, Parkland Health Center, and Barnes-Jewish St. Peters Hospital. For patients needing specialized oncology treatment, pediatric cardiac surgery, or a high-risk delivery, these are the destination facilities in the region — losing in-network access to them is a meaningful change in the quality of care available under a plan.
What losing an in-network hospital actually means for you
On January 1, 2027, Aetna and Anthem Medicare Advantage members will still be able to walk into a BJC or WashU facility — but as out-of-network patients, which means higher out-of-network deductibles, higher coinsurance, and possible balance billing for amounts above what the plan pays. For a single planned procedure, the extra cost can easily run into the hundreds or thousands of dollars.
The disruption is worst for patients mid-treatment: someone partway through cancer care at Siteman or a surgery schedule at Barnes-Jewish may need to either switch providers mid-course or stay and pay out-of-network rates. Most Medicare Advantage plans have continuity-of-care protections that can temporarily extend in-network benefits for ongoing treatment when a provider leaves the network — but these are limited in time, and the plan decides what counts as ongoing treatment. It is also worth noting that insurers often reach last-minute deals: Anthem's own update page for members stresses there are "no changes at this time" and that BJC remains in network through December 31, 2026. A deal could theoretically still be reached — but letters are already in patients' mailboxes, so affected members should shop as if the split will happen.
What to do now: 5 steps before December 7
- Check whether your doctors and hospital are in any plan you are considering. Use Medicare Plan Finder to confirm the 2027 provider networks of plans available in your county. Do not assume a plan keeps your hospital — provider networks change every year, and this year's network exit is proof.
- Read your Annual Notice of Change (ANOC). Your current plan mails it every fall. It lists exactly what changes for 2027 — networks, premiums, drug tiers, prior-authorization rules. Your hospital leaving the network is a textbook re-shop signal.
- Compare your 2027 options side by side. You can switch to a different Medicare Advantage plan that still includes BJC and WashU in network (UnitedHealthcare is the region's largest MA carrier and was not named in this dispute), or drop into traditional Medicare plus a Part D plan, optionally with a Medigap policy. Pair your search with the 2027 Star Ratings — our guide to the 2027 Medicare Advantage Star Ratings shows which large carriers improved and which slipped.
- If you are mid-treatment, ask about continuity of care. Call your plan before January and ask what temporary protections apply if your provider exits. Get the answer in writing if possible.
- Remember the wider 2027 context. This network exit lands in a year when at least 3.8 million MA enrollees nationally must find new coverage as insurers exit markets — our 2027 Medicare Advantage open enrollment guide explains why insurers are pulling back and how to re-shop. With open enrollment ending December 7, 2026, changes you make now take effect January 1, 2027 — the same day BJC goes out of network.
Frequently asked questions
When does BJC HealthCare leave the Aetna and Anthem Medicare Advantage networks?
January 1, 2027. The contracts expire December 31, 2026, and BJC and WashU Medicine confirmed on October 20, 2026 that renewal talks failed, per the St. Louis Post-Dispatch. Members can continue using BJC facilities at in-network rates through the end of 2026.
How many people are affected by the BJC network exit?
About 85,000 Medicare Advantage enrollees in the 15-county bi-state St. Louis metro area: just over 72,000 on Aetna and roughly 13,800 on Anthem, per federal data cited by the St. Louis Post-Dispatch.
Can I still go to Barnes-Jewish or Siteman Cancer Center on my current plan?
You can, but starting January 1, 2027 you will be treated as an out-of-network patient at BJC and WashU facilities — higher deductibles and coinsurance, plus possible balance billing. If those facilities are where you get care, switch to a plan that keeps them in network before open enrollment ends December 7.
Could BJC and the insurers reach a last-minute deal?
It is possible — hospital–insurer disputes are often resolved close to deadlines, and Anthem's member page still says there are "no changes at this time" to coverage through year-end. But patient letters announcing the exit are already out, so the safest move is to shop for 2027 coverage as if the split will happen. If a deal is reached, you can always stay.