creatinine /krē·at″inēn, -nin/ , a substance formed from the metabolism of creatine, commonly found in blood, urine, and muscle tissue. It is measured in blood and urine tests as an indicator of kidney function. Normal adult blood levels of creatinine are 0.5 to 1.1 mg/dL for females and 0.6 to 1.2 mg/dL for males; the numbers decrease in elderly patients because of a smaller muscle mass. See also creatine.
