The dosage of creatinine, blood (serum creatinine) or urinary (creatininuria) is used on the one hand to measure the activity of the kidneys and to diagnose a possible deterioration of renal function.

Creatinine analysis is also carried out to ensure muscle function, the latter being the result of a process of degradation in the muscles. Thus, the greater the muscle density, the higher the dosage of creatinine will also be. 

Summary

What is creatinine?

Creatinine analysis

What results can you expect from a creatinine test?

High creatinine level

Low creatinine level

La creatinine therefore comes from the degradation of creatine, itself synthesized by the liver and stored in muscles where it plays an important role in energy production. Muscle’s use of creatine produces waste products, the most notable of which is creatinine. This is carried by the blood, filtered by the kidneys and eliminated in the urine. Thus, comparing the level of creatinine in the blood to the amount of creatinine excreted in the urine makes it possible to assess the activity of the kidneys.

Note that the concentration of creatinine varies depending on the muscle mass of a person. Thus, men generally have a higher blood creatinine level than women.

How is the blood test for creatinine done?

L’exam sanguin consists of a venous blood test, usually at the bend of the elbow.

Since the creatinine level in the blood is linked to muscle activity, it is recommended that you stop any strenuous physical activity during the 48 hours preceding the examination. In addition, because red meat is rich in creatine, it is recommended to limit its consumption to less than 200 grams 24 hours before the examination, or even not to consume it at all. The consumption of drinks or diuretic products should be avoided the day before and the day of the examination.

Your doctor may also ask you to stop taking certain medications before the test.

How is the urine test for creatinine performed?

Urinary creatinine clearance, which measures the amount of creatinine withdrawn from the blood by the kidneys, is estimated from the total urine volume produced in 24 hours.

For this, the urine is collected in a single container provided for this purpose provided by the medical staff. Urine should be stored in the refrigerator.

The normal concentration of creatinine in the blood is between 6 and 12 mg / l (milligrams per liter) in humans and between 4 and 10 mg / l in women. These values ​​may vary depending on the source.

A normal calculation of urinary creatinine clearance is between 107 and 139 ml / min (milliliters per minute) in men under 40, and between 87 and 107 ml / min in women under 40.

A high concentration of creatinine in the blood may be a sign:

• impaired kidney function, such as kidney failure
• the presence of a kidney stone
• ischemia, in case of reduced blood supply to the kidney
• an infection
• chronic kidney disease
• kidney cancer in the most severe cases
• heart failure
• physical exhaustion
• dehydration
• muscle injury
• or even more rarely, from rhabdomyolysis (destruction of striated muscle tissue)

A high concentration of creatinine in the blood is associated with a low urine clearance. This is why the causes of low urinary creatinine clearance are the same as those discussed above.

A low level of creatinine in the blood may be a sign:

• low muscle mass caused by muscular dystrophy or simply age-related
• liver damage
• or a pregnancy

A large creatinine clearance may be a sign of carbon monoxide poisoning, or even hypothyroidism.