The company may be under criminal investigation for alleged irregularities in its Medicare business—but it's been touched by the Warren Buffett effect.

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

While the "vote of confidence" from Buffett's investment validates the long-term value of UnitedHealth shares, the "management needs to regain trust and credibility with investors, and get back to its beat and raise reputation of the past," said James Harlow, senior vice president at Novare Capital Management.

The conglomerate sold Apple shares during the second quarter, though the iPhone maker remains Berkshire’s largest stockholding.

Meanwhile, the healthcare giant pays an $8.84 annual dividend, yielding about 3.38%. UnitedHealth has raised its dividend for 15 consecutive years, including a 5.2% increase last quarter. You're collecting a sizable yield backed by roughly $30 billion in annual operating cash flow, giving you steady income while you wait for the recovery.

The Dow Jones Industrial Average opened at its first all-time high of the year on Friday as shares of health care giant UnitedHealth Group soared.

UnitedHealth Group completed its $3.3 billion purchase of Baton Rouge-based Amedisys Thursday morning, more than two years after plans to join the nation's two largest home health and hospice care companies were first announced.

Year to date, the stock has fallen by nearly 45%, which is by no means normal for the healthcare stock. In fact, this is the worst it has performed since the Great Recession, when it tumbled by more than 54% in 2008.

Warren Buffett's Berkshire Hathaway increased its holdings in UnitedHealth Group stock, and also added positions in D.R. Horton, Lamar Advertising, and Nucor.