Quest Diagnostics Falls 5.1% as CMS Moves to Cut Lab Payments Up to 15%

Quest Diagnostics (NYSE: DGX) stock fell 5.1% by 11:30 a.m. Tuesday after the Centers for Medicare & Medicaid Services disclosed it has been paying roughly 16% more for laboratory work than private insurers pay.

CMS said Monday it will cut reimbursement rates for lab costs by up to 15%, effective Jan. 1, 2027. The agency estimates the reduced rates will save taxpayers $1 billion per year.

Those savings come directly out of Quest's revenue stream.

The medical testing giant flagged this exact risk in its 10-K filing with the SEC. Quest warned of "the impact upon our testing volume and collected revenue or general or administrative expenses resulting from compliance with policies and requirements imposed by Medicare, Medicaid." It listed reduced Medicare and Medicaid rates as one key risk to investing in the stock.

Sizing the damage

The same 10-K filing shows Quest derived approximately 11% of its 2025 revenue from CMS reimbursement. The arithmetic follows directly: shrink an 11% revenue stream by 15%, and a full-rate cut would reduce Quest's annual revenue by 1.65%.

The exposure could compound. Quest notes that successive 15% annual reductions are possible from 2027 through 2029. Even under that scenario, the worst case works out to a reduction of slightly less than 5% of Quest's business.

With the stock down 5.1% on the news, that worst-case outcome is already more than priced into the shares. By that logic, there is little reason to expect continued declines after Tuesday's session, and the stock could even bounce back.

Why it matters

CMS pays above private-market rates today — about 16% more, by the agency's own account — and the scheduled cuts close that gap at the expense of the largest lab operators. For Quest investors, the market's 5.1% markdown already matches the ceiling on the projected revenue hit, leaving the stock's reaction looking less like a repricing and more like a one-time adjustment to a known, quantifiable risk the company itself disclosed months ago.