About 21,000 Medicare beneficiaries enrolled in UCare health plans are receiving letters this week that wrongly list monthly premium prices, making some think they are being charged $21 per month more than the true rate.

The problem is confined to Medicare subscribers with supplemental dental benefits from UCare who pay their premiums via electronic transfer of funds from bank accounts or the federal Social Security program, said Ghita Worcester, a senior vice president with Minneapolis-based UCare.

Two people contacted the Star Tribune this week about the problem, which UCare says did not result in any funds being wrongly transferred to the health insurer.

"We're in the process of getting a corrected letter out to folks along with an apology for the letter that was sent with the error in the amount on it," Worcester said. "Of course, you never want to have something like that happen, but the member did not have any amount taken from their accounts in error."

The mix-up comes during a stressful open enrollment season for many Minnesotans with Medicare coverage. Due to federal law, three large health insurers in the state had to eliminate across 66 counties a type of coverage called Medicare Cost plans, which were being used by more than 300,000 residents.

People losing Cost plans faced a choice between reverting to the original Medicare program or enrolling in a newer form of coverage called Medicare Advantage plans. UCare has been the state's largest provider of Medicare Advantage coverage for many years.

This letter that included the error is an annual statement for people who opt to pay premiums through Social Security or an electronic transfer from their bank, Worcester said. The statements erred by double-counting the $21 per month cost of the rider for dental coverage, she said, adding that subscribers previously received enrollment confirmations listing the correct premium amounts.

UCare says the supplemental dental coverage provides comprehensive benefits that are beyond the preventive dental coverage that's included in many of the company's health plans for Medicare subscribers.

Christopher Snowbeck • 612-673-4744 Twitter: @chrissnowbeck