THEurea is a molecule which results from a process of protein degradation. It is the main form of elimination of nitrogenous waste, through urine. It is the nitrogen of proteins which, combined with molecules produced by the liver, constitutes urea.

The urea assay, along with other measurements, makes it possible to assess the renal function, especially the presence of a renal failure. It is also prescribed to monitor kidney function in people with diabetes or who have had a myocardial infarction. This is because when the kidneys are no longer functioning normally, there is an increase in the levels of urea, creatinine and uric acid in the blood. Certain liver conditions can also affect the level of urea in the blood.

However, the dosage of urea alone in the blood is not very informative, because the amount of urea produced each day varies according to the diet and its excretion by the kidneys is irregular. The dosage of creatinine is therefore generally preferred, or at least carried out at the same time.

Urea can also be assessed in the urine (urea “clearance”). The urine urea to blood urea ratio can help the doctor determine the cause of kidney failure. The urea assay can also make it possible to evaluate the effectiveness of the dialysis.

The determination of urea in the blood (uremia) is performed on a blood sample, usually taken at the bend of the elbow.

You should preferably be on an empty stomach and avoid meals that are too rich in protein on the previous days.

The measurement of urea in the urine (uricemia) is done over 24 hours.

Normal values ​​for urea in the blood are between 2,5 and 7,6 mmol / L (or 0,10 to 0,55 g / L).

In children and pregnant women, these values ​​are lower.

In the urine, urea is found at 300 to 500 mmol / 24 hours.

Urea concentration increases abnormally in a variety of situations, including:

• in case of kidney failure or kidney damage
• in case of infections, cardiovascular accident, shock, stress, etc.
• when taking certain medications
• in case of a diet very rich in protein

Decreased urea levels may be a sign of dietary protein deficiency, for example, digestive malabsorption, or severe liver disease.