This assay allows to diagnose a dysfunction of the kidney filtration. The test is more reliable than that of urea.


Creatinine is a product of degradation of creatinine, largely eliminated by the kidneys. Its serum concentration thus depends on the renal elimination capacity.


Levy of 1 mL of blood on dry or heparin tube.

– Avoid hemolysis;

– Patient at rest.


Normal values:

– Man, 60 to 120 mmol / L;

– Woman, 50 to 110 mmol / L;

– Newborn: 60 to 90 mmol / L.

Down 30% of the glomerular filtration capacity does not affect creatinine.

In acute renal failure, the rise in creatinine is delayed.

The clearance may be low and normal serum creatinine; clearance is therefore a better review to monitor kidney failure.

In this case, a collection of 24-hour urine is necessary, carried out on antiseptics.



Practical advice:

Creatinine decreases during pregnancy and increases when excessive consumption of meat, a rhabdomiolyse (muscle lysis) or after exertion.

Some medicines affect the serum creatinine:

– Oral contraceptives increase it;

– Anticonvulsants, NSAIDS the decrease.

Creatinine depends on muscle mass, age, weight: in this case one must help calculating the clearance through the following formula:

clearance in mL / min = (140-age) x weight / 0.8 x creatinine in mmol / L.

kidney failure is:

– Moderate to an upper clearance 30 mL / min;

– Severe, for a clearance of 15 to 30 mL / min;

– Requires dialysis, to a clearance between 10 and 15 and less than 10.

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