2-Amino-1-methyl-5H-imidazol-4-one; formula: C4H7N3O; CAS Registry Number: 60-27-5

Break-down product of creatine phosphate in muscle and indicator for renal dysfunctions

Creatinine is a break-down product of creatine phosphate, a rapidly mobilisable energy reserve in the muscle. Creatinine is produced at a more or less constant rate which is influenced mainly by the muscle mass. It is transported to the kidneys where it is filtered out of the blood and excreted with the urine. In the case of renal dysfunction, the blood creatinine levels increase. This increase, however, is only significant when the filter efficiency of the kidneys has decreased by more than 50%. Blood creatinine is therefore not suitable for assessing beginning renal dysfunctions. These can better be detected by measuring the creatinine excretion, i.e. the creatinine concentration in the urine. Both parameters, blood and urine creatinine levels are used to calculate the creatinine clearance which is a measure for the efficiency of the kidneys to filter small molecules out of the blood.

The creatinine levels in blood and urine are therefore an indicator of renal functioning in humans.

The reference values for creatinine in blood plasma are 0.84 - 1.25 mg/dL for men younger than 50 years and 0.66 - 1.09 mg/dL for women of the same age class. The reference value for creatinine in urine of both men and women aged 20-29 is 23.8 ± 2.3 mg/kg/24h. The creatinine level in urine is commonly used for the normalisation of xenobiotics in urine to avoid possible biases caused by differences in urine dilution.


  • Student groups with an even number of female and male students at the age of 20 to 29.

Sampling area

Sampling period

1986 - 2019

Extended information


  • Labor und Diagnose - Indikation und Bewertung von Laborbefunden für die medizinische Diagnostik
    Thomas, Lothar
    Frankfurt am Main: Th-Books Verlag, 2005. 2016, 2005