Shares of UnitedHealth Group surged nearly 14% on Friday after billionaire Warren Buffett's Berkshire Hathaway bought 5 million shares of the company, providing a shot in the arm for investors who think the health conglomerate will turn around under its new CEO.

Berkshire Hathaway's $1.6 billion stake in UnitedHealth Group is helping to lift the Dow Jones Industrial Average to a new record as investors pile into healthcare sector funds.

UnitedHealth shares soared after Warren Buffett revealed a stake of 5 million shares, worth about $1.6 billion, in the troubled health insurer. The "Big Short" investor Michael Burry and Appaloosa Management's David Tepper also disclosed sizable stakes in the company.

Buffett owned UnitedHealth shares before selling his stake in 2010, though his Berkshire Hathaway recently acquired shares.

The blue-chip Dow opened at a record high on Friday, as UnitedHealth's shares jumped after Berkshire Hathaway raised its stake in the health insurer, while expectations of an interest rate cut in September also lifted the mood.

The blue-chip Dow briefly hit a record high on Friday, as UnitedHealth's shares jumped after Berkshire Hathaway raised its stake in the health insurer, while investors assessed mixed data to gauge the Federal Reserve's monetary policy path this year.