Creatinine-d3 contains three deuterium atoms. It is intended for use as an internal standard for the quantification of creatinine by GC- or LC-mass spectrometry. Creatinine is synthesized in kidney, liver, and pancreas and transported in blood to muscle and brain where it is phosphorylated to phosphocreatine. Some free creatine in muscle is converted to creatinine. The amount of creatinine produced is proportional to muscle mass. In the absence of renal disease, the excretion rate of creatinine in humans is relatively constant. Thus, urinary creatinine is commonly used as a key benchmark for the normalization of a variety of urinary biomarkers. Serum creatinine levels are a useful indicator of renal function. Abnormal creatinine levels have been implicated in diabetes and in cardiovascular and circulatory diseases.
