UnitedHealth Group and Humana confirmed Tuesday that they will drop Medicare Advantage plans covering more than one million American seniors in 2027, marking one of the largest coverage disruptions in the program's history. Both insurers cited rising medical costs and tighter federal payment rules as reasons for the withdrawal.

The announcements came days before the Medicare annual enrollment period opens on October 15, giving affected beneficiaries roughly six weeks to select new coverage. UnitedHealthcare said it would exit unprofitable county markets, while Humana confirmed it is reducing its plan footprint to restore margins after heavy losses.

The retreat follows years of expansion in Medicare Advantage, which now enrolls more than half of all Medicare beneficiaries. Insurers have blamed the Centers for Medicare and Medicaid Services for risk-adjustment changes and reimbursement rates that failed to keep pace with utilization among older patients.

The Centers for Medicare and Medicaid Services urged affected seniors to review replacement options during open enrollment, warning that those who take no action may be defaulted into different plans or revert to traditional Medicare. Patient advocates at the Medicare Rights Center said many beneficiaries face losing established doctor networks and prescription coverage.

The disruption compounds pressure on an already strained system. It comes alongside the Independence Blue Cross settlement over Medicare Advantage overpayments and legal fights over premium increases in California. Analysts at major Wall Street firms have forecast further consolidation as insurers prioritize profitability over enrollment growth.