UnitedHealth Group is under criminal and civil investigation by the DOJ over alleged Medicare fraud, raising serious questions about billing practices and industry oversight.

UnitedHealth shares tumbled Thursday after the health insurance giant confirmed that it’s the subject of a Department of Justice investigation. Monitor these key chart levels.

Shares of UnitedHealth Group fell sharply in premarket trading Thursday after the healthcare giant said it was “complying with formal criminal and civil requests” from the U.S. Department of Justice.

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UnitedHealth Group is scheduled to report second-quarter results on Tuesday morning, capping a tumultuous first half of the year for the health insurance giant.

UNH braces for a 27% earnings drop in Q2 as soaring medical costs, margin pressure and investor jitters weigh on performance.

Stocks were mixed Thursday and the Dow Jones Industrial Average declined as UnitedHealth Group fell after saying it was “complying with formal criminal and civil requests” from the U.S. Department of Justice, and as IBM slumped following its second-quarter earnings.