Creatine and p-creatine are converted non-enzymatically to creatinine, which enters the blood and is excreted by the kidneys via glomerular filtration. The analysis of creatinine in serum and urine is an important clinical test for renal disease and dysfunction. Creatinine is removed from plasma by the glomerulus and then excreted in the urine without any appreciable resorption by the tubules. This “creatinine clearance” from the body is used to measure glomerular filtration rates. Cell Biolabs’ Urinary Creatinine Assay Kit is based on the Jaffe reaction, produces an orange-red color complex that can be measured with a standard spectrophotometric plate reader. Each kit provides sufficient reagents to perform up to 192 assays, including blanks, creatinine standards and unknown urine samples. High concentrations of ascorbic acid, uric acid, glucose, ketones and cephalosporin antibiotics may interfere with the assay causing falsely high values.