UnitedHealth Group stock has been rallying on news that Berkshire Hathaway has invested in the business. Warren Buffett is the CEO of Berkshire Hathaway and the investment could be seen as a possible vote of confidence in UnitedHealth's business.

UnitedHealth shares clocked the largest one-day percent increase since March 2020, as tracked by Dow Jones Market Data Group. It was on pace for the best day in 17 years before giving back some of those gains. For the week, shares rose over 21%, the best week since May 2009. Still, the stock is down more than 50% over the past 12 months.

Beaten-down UNH is set to challenge its 50-day moving average after a major vote of confidence from the Oracle of Omaha.