Creatinine normalization

When evaluating specimens testing positive over time, the concentration of the urine itself may complicate the interpretation. To eliminate urine concentration as a factor, a calculation called creatinine normalization is performed. Creatinine is a substance produced in the body and excreted in the urine. The presence of creatinine indicates that the specimen is urine, and the level of creatinine is an indicator of the concentration of the urine. The higher the creatinine value, the more concentrated the urine specimen is. The lower the creatinine value, the more dilute the urine specimen is.

The creatinine level fluctuates based on fluid intake. The creatinine normalization calculation corrects or normalizes the creatinine level of the specimen to that of an industry standard and then applies that correction or normalization factor to the drug result. This calculation corrects for fluctuation of the urine concentration and presents a clearer picture of the drug level in the sample and simplifies interpretation of drug levels in drug tests over time.