Creatinine is excreted at fairly constant rates in the absence of renal disease and commonly used as benchmark in urinary biomarker analysis. Serum creatinine levels are useful indicators of renal function and have been implicated in diabetes, cardiovascular and circulatory diseases. This stable-labeled internal standard is suitable for quantification of creatinine levels by LC/MS or GC/MS for applications in clinical diagnostic, urine drug testing or forensic analysis.