Health care has been the worst-performing sector in the stock market this year, rising by just 4.17% as of Monday's close, significantly lagging the broader market indexes. The Dow Jones Industrial Average is up 13.35% over the same period, and the S&P 500 is 16.12% higher.
The biggest decliners have been from insurers, which are under threat from "Medicare for All" proposals. Investors are also watching the Trump administration's legal challenge to former President Barack Obama's signature health insurance law, the Affordable Care Act.
A federal appeals court in New Orleans said last week that it will hear arguments in July on a lawsuit backed by President Donald Trump to overturn Obamacare. Dismantling the health-care law would lead to 32 million more uninsured people in the U.S. by 2026, according to an estimate from the Congressional Budget Office.
Earlier Tuesday, UnitedHealth reported first-quarter earnings and revenue that beat Wall Street's expectations. It was driven by strength in its pharmacy benefit management business and higher enrollment for its health plans.
The industry bellwether, which is the first health insurer to report quarterly results, also raised its full-year adjusted earnings forecast to between $14.50 and $14.75 per share from its prior projection of $14.40 to $14.70 a share.
— CNBC's Bertha Coombs contributed to this report.