Pamela Smith was surprised to receive an email from InterMed on Thursday telling her they will no longer accept her insurance, Martin’s Point Medicare Advantage, starting in January.

“This was all out of the blue,” said Smith, of North Yarmouth, on Friday. “I don’t understand it. I’m trying to figure out what I’m supposed to do.”

Portland-based InterMed issued the notice “more than eight months in advance, so that our patients have time to review their options and make the best decision for their care,” Dr. Phyllidia Ku-Ruth, president of the medical group’s board, said in a written statement on Friday.

Ku-Ruth said that “this decision was not made suddenly or lightly” for the estimated 4,500 InterMed patients who have a Medicare Advantage plan offered by Portland-based Martin’s Point Health Care.

“Over the last several years, we have consistently raised concerns that the structure of our agreement was making it increasingly difficult to deliver the high-quality care our patients need and deserve while maintaining a sustainable practice environment for our teams,” Ku-Ruth said.

Steve Amendo, a spokesperson for Martin’s Point, said in a statement on Friday that “the announcement was unexpected, and communications were sent to impacted members without meaningful prior discussion with Martin’s Point and in advance of formal notice of intent to leave our network at year-end.”

In addition to selling insurance plans, Martin’s Point Health Care offers primary care and specialty care services.

Medicare Advantage is insurance for those 65 and older that’s an alternative to Medicare. Medicare Advantage plans offer many of the same benefits as Medicare, but will also typically include additional benefits, such as vision, hearing and dental. Some will require monthly premiums to pay for the benefits not included in Medicare.

Before January, InterMed patients with a Martin’s Point Medicare Advantage plan can either change insurance carriers, switch to a new practice that accepts their insurance or pay out-of-pocket for care at InterMed, according to an email sent to patients that Smith shared with the Portland Press Herald. The Martin’s Point plans will be accepted at InterMed through Dec. 31.

Smith said she has always liked her Martin’s Point plan, which she and her husband have had for more than a decade. But she also likes her primary care and specialist doctors and plans to switch insurance plans so she can keep going to InterMed, which has locations in South Portland and Yarmouth.

“I’m offended,” said Smith, who has been an InterMed patient for over a decade. “We’ll figure out a way to stay with InterMed, but it’s very bizarre.”

Mitchell Stein, a Maine-based independent health policy analyst, said on Friday that patients have many Medicare Advantage plans to choose from that offer similar benefits.

“This is giving people plenty of notice,” Stein said.