UnitedHealth Group’s (UNH) outlook cut Thursday has raised concerns about its insurance peers, with several set to report earnings in the coming weeks.

The company on Thursday reported first-quarter results that missed estimates, and cut its profit forecast for 2025, pointing to higher-than-expected medical costs for people enrolled in Medicare plans.

UnitedHealth expected claims in its Medicare Advantage business to rise at a similar rate to 2024, but CEO Andrew Witty said in Thursday’s earnings call that “indications suggest care activity increased at twice that rate,” according to a transcript from AlphaSense.

Jefferies analysts said Thursday that UnitedHealth’s “peers are in trouble” if the bellwether‘s issues are applicable to insurance rivals. However, the analysts said it’s also possible UnitedHealth’s “expectations were materially more aggressive than peers.”

UnitedHealth shares lost over a fifth of their value on Thursday, in their worst day in decades. Other health insurance stocks were dragged down with it, as Humana (HUM) sank more than 7%, Elevance Health (ELV) fell 2.4%, and CVS Health (CVS) slid 1.8%.

Elevance is set to report earnings next Tuesday. Humana is scheduled to release its results the following Wednesday, with CVS’s report due a day later.