UnitedHealth Group reported a surge in third-quarter medical costs on Tuesday, as the company struggled with lower government payments in its insurance business and persistently high demand for medical care,

UnitedHealth’s stock was having its worst day in more than four years on Tuesday, after the healthcare giant beat third-quarter profit and revenue expectations but missed on medical-care profitability and lowered its full-year outlook.

Quarterly profit of $6.06 billion at the Minnetonka-based company beat analyst estimates on a per-share basis as revenue grew 9% over last year.

UnitedHealth Group's third-quarter medical costs exceeded Wall Street estimates on Tuesday, as the insurer paid out more due to persistently high demand for healthcare services and received lower reimbursements on government-backed insurance plans.