WHAT IS CREATININE (URINE) TEST?
Creatinine is produced continuously as a nonprotein end product of anaerobic energy-producing creatine phosphate metabolism in skeletal muscle. It is continually and easily excreted by the renal system by glomerular filtration. Decreased levels of urine creatinine indicate a slowing of the glomerular filtration rate. Creatinine is thus a very specific indicator of renal function. A diurnal variation in creatinine may be related to meals, with troughs occurring around 0700 (7 AM) and peaks occurring around 1900 (7 PM). Because this test involves the collection of a 24-hour urine sample, it captures the effects of both peaks and troughs of creatinine levels.