UNH has lost more than $200 billion in market value in the last six months. The company’s old CEO sees a fix. Investors should be wary.

Shares of UnitedHealth Group ( UNH 3.45%) are plummeting this week. The company's stock is down 27.4% as of 12:29 p.m. ET. The collapse comes as the S&P 500 ( ^GSPC 0.27%) gained 4.7% and the Nasdaq-100 gained 6.4%.

Shares of UnitedHealth Group (NYSE: UNH) are falling on Thursday. The collapse comes as the S&P 500 gained 0.1% and the Nasdaq Composite fell 0.4%. The troubled health insurance giant is facing reports of a Department of Justice (DOJ) investigation into possible Medicare fraud.