(Bloomberg) -- The largest US health insurers jolted investors twice in the span of three days with cuts to their forecasts that sent stock prices tumbling — leaving Wall Street wondering whether more surprises lay ahead.

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Elevance Health Inc. said Thursday that adjusted earnings per share will be flat this year and rise more slowly than it had targeted for 2025. That followed Tuesday’s disappointing forecasts through the end of next year from rival UnitedHealth Group Inc.

Between Monday’s close and Thursday morning, the news erased $55 billion from the companies’ combined market value. Elevance shares lost as much as 20% Thursday, while United Health lost 8.1% the day it issued its outlook. For each, it was the biggest intraday drop since March 2020, when fears of the emerging pandemic’s health toll temporarily sent the industry reeling.

Insurers have enjoyed years of growth driven by Medicare and Medicaid, government health programs that cover about more than one in three Americans. Now, the companies face rising challenges in the taxpayer-funded business lines as costs for Medicaid patients rise and Washington cracks down on Medicare payments that officials have said are too high.

Elevance blamed its miss on outsized costs in its Medicaid business for low-income Americans. States have cut 14 million people from the safety net health program since early 2023, unwinding an expansion of coverage that dated from Covid-19 emergency measures.

Executives cited “unprecedented challenges” in Medicaid but had little to say about how they were caught flat-footed by such a widely anticipated event. Elevance management “showed an almost shocking lack of transparency” about what’s behind the fast-rising costs, said Spencer Perlman, an analyst at policy research group Veda Partners.

Medicaid Difference

In most business lines, insurers can raise prices once a year, so if they underestimate future costs they can correct course. Medicaid is different. Insurers bid on multi-year contracts to run state health programs.

If they find rates to be insufficient in the middle of a contract, they can haggle with states for more money, but getting it may take a while, as Elevance executives acknowledged. States often base decisions on data a year old, Elevance Chief Executive Officer Gail Boudreaux told analysts Thursday.