Stephen Hemsley ran UnitedHealth Group for more than a decade. It's a different company after four years with Andrew Witty in charge.

Even UnitedHealth will struggle to overcome parasitic medical costs that Warren Buffett once called a tapeworm eating away at U.S. economic competitiveness. The $300 billion healthcare conglomerate reinstalled Chairman Stephen Hemsley as CEO and yanked its financial guidance.

UnitedHealth just made a surprising move, bringing back a familiar face to fix what’s been a rough year.

Stephen J. Hemsley returned as CEO after Andrew Witty's surprising decision to leave the insurance giant. UnitedHealth's stock fell 17% on Tuesday.

Former CEO and current chairman Stephen Hemsley is stepping back into the top job following the abrupt resignation of Andrew Witty, UnitedHealth said.

UnitedHealth CEO Andrew Witty is stepping down for personal reasons and the nation’s largest health insurer suspended its full-year financial outlook due to higher-than-expected medical costs. Hemsley was UnitedHealth Group CEO from 2006 to 2017. He will remain chairman of the company’s board. Witty will serve as a senior adviser to Hemsley.

UnitedHealth Group Chief Executive Officer Andrew Witty stepped down, effective immediately, "for personal reasons", the company said Tuesday. “Leading the people of UnitedHealth Group has been a tremendous honor as they work every day to improve the health system, and they will continue to inspire me,” Witty said in a statement shared by UHG.

Robyn Denholm has earned five times as much as UnitedHealth Group's Stephen Hemsley, the next non-executive chair most prone to liquidating stock.