(Reuters) -U.S. insurers are requesting the biggest premium increases for Obamacare plans since 2018, according to an analysis by health-research firm KFF, prompted by the looming expiry of premium tax credits and potential tariffs on medical goods.

Insurers are proposing a median premium increase of 15% for 2026, KFF said, citing data from rate filings of 105 insurers across 19 states. In recent years, premiums in the plans have been relatively flat or grown only modestly.

The industry has been struggling with changing enrollment patterns and rising medical costs. Insurers such as UnitedHealth and Centene ( CNC ) have suspended their annual earnings forecasts while others have lowered their profit targets.

Insurance companies pointed to the slower market growth and a rise in higher-risk patients enrolled in plans under Affordable Care Act, or Obamacare. The plans primarily serve people who do not get insurance either through an employer, Medicaid for low-income people or Medicare for older adults.

The companies also cited the planned 2026 expiration of COVID-era premium tax credits as a reason, with KFF's analysis showing insurers will raise premiums by an additional 4% than they would if the enhanced tax credits were renewed.

For 2026, insurers generally reported that the underlying cost of healthcare remains around last year's 8% increase.

Several noted that GLP-1 weight-loss and diabetes drugs are driving costs higher, along with labor market pressures affecting negotiations with healthcare providers.

Insurers also flagged uncertainty surrounding the "ACA Integrity Rule", a set of regulations finalized to strengthen verification and reduce improper enrollments in Obamacare plans, according to the report.

Health insurers Centene ( CNC ), Molina, UnitedHealth, Cigna, Elevance, CVS Health, Oscar Health and Kaiser Permanente did not immediately respond to requests for comment.

(Reporting by Christy Santhosh in Bengaluru; Editing by Sriraj Kalluvila)