Andrew Witty Photo by Chatham House/CC

Just about five-and-a-half years after his promotion to CEO of UnitedHealth Group, Andrew Witty is stepping down for “personal reasons,” the company announced Tuesday.

Stephen Hemsley, who served as the health insurer’s CEO from 2006 to 2017, will again take over as chief executive. Hemsley will also remain chair of UnitedHealth Group’s board, while Witty will serve as an adviser to him.

The leadership change comes at a challenging time for the company. In Tuesday’s news release, UnitedHealth officials said the company is suspending its financial outlook for 2025 due to increasing medical costs.

“The medical costs of many Medicare Advantage beneficiaries new to UnitedHealthcare remained higher than expected,” the company said in the release.

Meanwhile, the fatal shooting of UnitedHealth executive Brian Thompson in New York City in December thrust many Americans’ frustrations with health insurance back into the spotlight.

Under Witty’s leadership, the company’s stock price grew by about 60%, though it’s seen a decline within the past five months, the Associated Press reported.

Before he became CEO, Witty was chief executive of the company’s Optum division.

There could be more trouble ahead for UnitedHealth. A day after the company announced the CEO transition, the Wall Street Journal reported that the Department of Justice is investigating UnitedHealth Group for “possible Medicare fraud.” The insurer told the Journal that it hadn’t been notified of such an investigation, and that it stands “by the integrity of our Medicare Advantage program.”

UnitedHealth is already facing “a list of government inquiries,” the Wall Street Journal reported.