HealthPartners said Tuesday it will add Allina Health System next year to the network of doctors and hospitals in its Medicare Advantage health plans.

It's another sign of how the state's Medicare market continues to be in flux following the elimination of Medicare Cost health plans across much of Minnesota at the start of the year.

"We're expanding access to clinicians and hospitals to further meet our members' needs," said Jim Eppel, the chief administrative officer at HealthPartners, in a statement.

For 2019, more than 300,000 people with Cost plans in Minnesota had to switch coverage due to a federal law that enacted a long-delayed change to save money by eliminating Cost plans in counties where there's significant competition from Advantage plans.

About 1 million Minnesotans get health insurance though the federal Medicare program and the coverage typically comes through one of three channels — Cost plans, Advantage plans and original Medicare. Elimination of the Cost plans in 66 counties this year meant those consumers faced a choice between the original Medicare program, which provides access to almost all doctors, and Medicare Advantage plans that in many cases have a limited network of health care providers.

With the shift, Minneapolis-based Allina launched its own Medicare Advantage health plans through a joint venture with the national health insurer Aetna, while Bloomington-based HealthPartners sold Medicare Advantage coverage with a relatively tight network of doctors and hospitals. For consumers seeking a wide choice of doctors and hospitals, HealthPartners emphasized Medicare Supplement policies, also called "Medigap," that work in conjunction with the original Medicare program.

A Star Tribune analysis in June showed that HealthPartners saw its overall Medicare enrollment drop between December and March by about 13,000 people, or 21%. The decline featured a big drop in Cost plan enrollment at HealthPartners that wasn't completely offset by growth in Advantage plans and Medigap customers.

"We see this evolution in Medicare as a multiyear process," the insurer said in a June statement.

Cost plans and Advantage plans are similar in being forms of Medicare coverage sold by private health insurers, but they differ in how the government pays health plans.