The letter also said, among other complaints, that the Louisville, Ky.-based insurer created confusion by not adequately disclosing which providers were in-network and does not comply with required appeals processes.
The complaints come at a time when the popularity of Medicare Advantage plans has been escalating. And Minnesota has the highest percentage of Medicare beneficiaries enrolled in an MA plan, at 49%—compared with 28.8% of beneficiaries nationwide, the letter said. Humana has 17% of the Medicare Advantage market in Minnesota, according to Swanson's office.
Swanson wrote that she was asking the CMS to pursue an investigation because states do not have the authority to enforce Medicare Advantage plan rules and make benefit determinations.
Kate Marx, a spokeswoman for Humana, said the company has not been notified by either the Minnesota Attorney General's office or the CMS about the action. “We take this very seriously and are working to identify the facts,” she said, adding that the plans have received a quality rating of 4.5 stars out of five.
Humana reported $24.9 billion in revenue from Medicare Advantage premiums for 2012, according to its annual report. Individual MA plans generated 53.7% of Humana's revenue that year while group MA plans contributed another 10.5%.
The company did not break out revenue figures for Minnesota, where it covers 100,000 beneficiaries, according to Marx.
Follow Beth Kutscher on Twitter: @MHbkutscher