More than 38,000 Medicare beneficiaries with health plans from Blue Cross and Blue Shield of Minnesota are wrongly receiving termination notices, prompting the Eagan-based insurer to begin calling subscribers to explain the mistake.

The letters are related to the elimination of Medicare Cost health plans at the end of the year, which will prompt true health plan terminations for an estimated 320,000 seniors across much of Minnesota.

The change won’t affect consumers in 21 Minnesota counties — including Duluth and the state’s northeast corner — but those are the Blue Cross customers who were wrongly sent the termination notices, according to statements Tuesday from Blue Cross and the federal Centers for Medicare and Medicaid Services (CMS).

The federal agency said Blue Cross provided the government with bad information, which explains why CMS sent about 38,700 enrollee letters.

“CMS reached out to affected plans to ask them to provide information on which enrollees should receive nonrenewal notices,” the agency said in a statement to the Star Tribune.

“One of the plans, Blue Cross Blue Shield of MN, inadvertently sent us incorrect enrollment [information] for 21 counties resulting in CMS sending nonrenewal notices to enrollees in these counties even though the counties are not being non-renewed,” CMS said. “BCBS/MN recognized its error and we are working together to swiftly resolve this issue on behalf of beneficiaries.”

In addition to making phone calls, Blue Cross said Tuesday in a statement to the Star Tribune: “In the coming weeks, these members also will receive mailed materials from Blue Cross that confirm the availability of their same plan for next year.” The insurer has posted information on its website about the change, as well.

Health insurers and the federal Centers for Medicare and Medicaid Services (CMS) are notifying Minnesota consumers about a big change coming for many with Medicare health plans. For more than a year, insurers have been sizing up the shift, with health plans as well as state and federal officials providing more information to consumers over the past few months.

Cost plans have been a way for beneficiaries to obtain Medicare coverage via private health plans, much like Medicare Advantage plans that are popular across much of the country. The two types of health plans differ in how they’re reimbursed by the government, and Minnesota is one of the few states in the nation where a large number of people buy Cost plans.

A federal law passed in 2003 created a “competition requirement” for Medicare Cost plans, which stipulated the plans could not be offered in service areas where there was significant competition from Medicare Advantage plans. Congress delayed implementation of the requirement several times until a law passed in 2015 that called for the rule to take effect in 2019.

Blue Cross, Bloomington-based HealthPartners and Minnetonka-based Medica collectively sell Medicare Cost plans that cover about 370,000 Minnesotans.

Of those, about 50,000 live in the 21 counties where the Cost plans won’t be going away, with the large majority buying coverage from Blue Cross.

“We are aware that Medicare plan termination letters were sent out in error from the Centers for Medicare & Medicaid Services to many of our members,” Blue Cross said in a statement. The insurer says about 40,000 people in the 21 counties are enrolled in the Platinum Blue health plan.

CMS said in a statement that it “will continue to monitor the situation and work with Blue Cross Blue Shield of MN to ensure beneficiaries get corrected information.”

Cost plans from Blue Cross, HealthPartners and Medica will not be terminated in the following 21 counties: Aitkin, Carlton, Cook, Goodhue, Itasca, Kanabec, Koochiching, Lake, Le Sueur, McLeod, Meeker, Mille Lacs, Pine, Pipestone, Rice, Rock, Sibley, St. Louis, Stevens, Traverse and Yellow Medicine.

In the remaining 66 counties including the Twin Cities metro, an estimated 125,000 with Cost plans will be automatically enrolled in comparable Medicare Advantage plans from their current insurer unless they opt for a different health plan. HealthPartners and Medica have been notifying those subscribers about what their conversion coverage will look like, and Blue Cross says it will do so this month.“Different insurers have different names for their Cost Plans,” said the state Commerce Department in a fact sheet on the transition that includes a map of affected counties. “Seniors can call the phone number on the back of their health plan member card to find out if they have a Cost Plan.”

The state estimates that another 195,000 people in counties where Cost plans are going away will need to take action to obtain replacement coverage. That means signing up for a Medicare Advantage plan or obtaining a Medicare Supplement policy, often called a “Medigap plan.”

Consumers will get full information about health plan options for 2019 on Oct. 1. The open enrollment period begins Oct. 15.