S&P Global Ratings revised Birmingham, Ala.-based UAB Medicine's outlook to negative from stable.
S&P also affirmed its "AA-" long term rating on the health system's revenue bonds.
The outlook revision is a result of UAB Medicine's weaker operating margins in the last two fiscal years, which resulted in a lowered annual debt service coverage. The new maximum annual debt service coverage is not in line with its current "AA-" long-term rating.