Berkshire Hathaway, Buffett’s investment group, disclosed it had bought 5 million shares of the healthcare company earlier in the year. That sparked a 14% Friday rally in a stock that has lost more than half of its value over the past 12 months.

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.

The Oracle of Omaha just took a $1.6 billion stake in the battered healthcare giant, sending shares soaring 9% after hours.