Medicare Shock: Insurance Giant Loses 54 Trillion Won in One Day

On the 27th, UnitedHealth Group (UnitedHealth Group Inc: UNH) plunged 19.63% on the New York Stock Exchange, closing at $282.80 per share. Trading volume topped 370 million shares, and its market capitalization fell to about $256.1 billion, wiping out roughly $42 billion in value in a single day.

The sell-off was triggered by guidance issued alongside its 2025 results, which suggested that 2026 revenue could dip slightly to around $439.6 billion—below market expectations. Investor worries were compounded by reports that the Trump administration proposed only a 0.09% increase in Medicare Advantage premiums for 2027, sending the entire health insurance sector sharply lower.

According to local media, UNH recorded full-year 2025 revenue of $447.6 billion, up 12% year-over-year, but fourth-quarter net income plunged from $2.8 billion the previous year to about $200 million, hit by cyberattacks and restructuring charges. Although the company forecast adjusted EPS of at least $17.75 for 2026, concerns over the revenue outlook and weakening Medicare Advantage profitability cooled investor sentiment markedly.

UnitedHealth Group is the largest private health insurer in the U.S. and a comprehensive healthcare company that spans Medicare Advantage, Medicaid and the ACA exchanges, anchored by two main divisions: insurance arm UnitedHealthcare and healthcare services platform Optum. Long favored by institutional investors for decades of steady revenue growth and dividends, the company’s growth story has come under scrutiny in recent years amid tougher Medicare regulations, surging medical costs, cyber threats and executive turnover.