The measurement of the creatinine level, or creatinine, allows you to know if the kidneys are working well. This analysis can be done in the urine (urinary creatinine) or the blood and detect a possible renal insufficiency. Norms in women and men.
The measurement of Creatinine level helps to assess kidney function. In other words, it allows you to know if the kidneys are working well. This rate may vary from one individual to another. On the other hand, it is very stable for the same person. At a jock, for example, we observe a higher creatinine level than the average because the muscles work more intensely and therefore produce more creatinine. There muscle mass in general therefore plays on this rate just like physical activity, a protein-rich diet, age or weight of the individual. THE creatinine dosage is often associated with research albuminuria (protein in the urine), which is another marker of kidney damage.
What is creatinine?
Creatinine is a substance derived from the breakdown of creatine (natural amino acid derivative) of skeletal muscle. She constitutes organic wasteNormally evacuated in the urine after renal filtration. The measurement of its rate has the essential role ofassess renal function. The creatinine level in a given individual is constant, on the other hand, it is important to calculate creatinine clearance, that is to say the ratio between its quantity brought by the plasma and that eliminated by the kidney. The variation of this rate will make it possible to know the functional state of the kidney.
What is the normal level for urinary creatinine?
The dosage of urinary creatinine is done by collecting urine produced by the patient over a period of 24 hours. The urine is collected in a container kept at low temperature. In accordance with the indications noted on the analysis sheet, the results should normally be between 8 and 16 mmol/24 hours in women Or 9 and 18 mmol/24 hours in men. This difference is related to the fact that the muscle mass of women is lower than that of men.
| Women | Between 8 and 16 mmol/24 hours |
| Male | Between 9 and 18 mmol/24h |
The standards differ according to the techniques used by the laboratories. Note that the results do not constitute a diagnosis. It is therefore essential to plan the consultation of a doctor to jointly plan with him additional examinations or a possible treatment.
What is the normal level of creatinine in the blood?
When the ability of the kidneys to eliminate waste decreases, the amount of creatinine increases in the blood. THE DFG or glomerular filtration rate is estimated by the creatinine clearance calculation according to the blood creatinine level, but also the age, sex and weight of the individual. The clearance of a molecule corresponds to its capacity for purification by an organ. Three formulas exist:
- the Cockroft formula established in 1976 but almost no longer used.
- the formula MDRD (Modification of Diet in Renal Disease Study) (2006)
- the formula CKD-EPI (2009)
There Haute Autorité de Santé recommends using the CKD-EPI formula from serum creatinine measured by enzymatic method, failing which the MDRD formula if serum creatinine is measured by colorimetric method (so-called Jaffé method). Creatinine clearance is used to diagnose renal failure. It is reduced in the event of renal insufficiency and its level is correlated with the severity of this insufficiency.
- The GFR is normal between 90 and 120 ml/min/1.73 m2
- Between 60 to 89 ml/min/1.73 m2: chronic renal failure is mild.
- A GFR of less than 60 ml/min/1.73 m2 defines chronic kidney disease.
What causes high creatinine?
Creatinine levels are increased in cases ofkidney failure or strenuous physical or muscular activity. If the amount of creatinine is higher than the average readings given, this may indeed indicate a kidney dysfunction. Unfortunately, the increase in creatinine level, when it is a sign of kidney failure, does not cause symptoms and it can be discovered late.
What causes low creatinine?
Low creatinine may be a sign of muscle atrophy, related to myopathy. It is often accompanied by symptoms such as severe muscle weakness, weight loss and fatigue.
When to worry?
Outside of sports, a high creatinine level requires a consultation and at least one control a few days later to see the evolution. The search for the causes is necessary: infectious context, diabetes, toxic drugs for the kidneys….
To keep your kidneys healthy, you must:
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Source: Elevation of serum creatinine, CUEN, 2018.
Thanks to Dr. Brigitte Lantz, nephrologist at Necker Hospital and Secretary General of the Kidney Foundation for her validation.