UnitedHealth (UNH.US) reported a better-than-expected third-quarter performance, but the company lowered the high end of its full-year guidance due to rising medical costs and the impact of a cyberattack. The company expects adjusted EPS to be between $27.50 and $27.75 in 2024, lower than the previous expectation of $27.50 to $28.00.The stock price of UnitedHealth fell 3.53% to $584.00 in pre-market trading, as the new guidance midpoint was below analysts' average expectations.UnitedHealth reported Q3 revenue of $100.8 billion, up 9.1% YoY, topping the market's expectation of $99.2 billion; adjusted EPS was $7.15, topping analysts' average expectation of $6.99.UnitedHealth's medical loss ratio (an important indicator of patient care expenses) was 85.2%, below Wall Street's expectations, the company said, due to pressure on its Medicare program for older Americans. Days payable outstanding was 47.4, compared to 45.2 in the second quarter of 2024 and 50.7 in the third quarter of 2023.U.S. health insurers have been struggling with unexpected medical cost increases and reduced government program spending. UnitedHealth, the first company in the industry to report its performance, is seen as a bellwether.The new guidance covers the impact of a major cyberattack on the company's health care unit, which was larger than UnitedHealth had previously anticipated. Some costs related to the crisis were excluded from the adjusted results.