Urea test: what it is for, values ​​(and high or low urea)

The urea test measures the amount of this substance in the blood, with the aim of evaluating whether the kidneys and liver are functioning.

When there are problems with the liver, kidneys or when you have a diet very rich in proteins, for example, the amount of urea in the blood increases, characterizing a condition known as uremia, which is toxic to the body. Know how to identify the symptoms of uremia.

Most of the time, the urea test is requested together with other tests, mainly creatinine, as this makes it possible to better assess the functioning of the kidneys for blood filtration. See more about the creatinine test.

What is urea

Urea is a substance produced by the liver from dietary proteins and its production can be altered when there are problems with the kidneys or liver. This happens because dietary proteins are transformed into urea in the liver and the urea is filtered by the kidneys and eliminated in the urine.

What is it for

The urea test is mainly used to evaluate the functioning of the kidneys and monitor the evolution of kidney diseases.

The test may also be requested when there are symptoms of excess urea or kidney problems, such as excessive tiredness, increased blood pressure, foamy or bloody urine or swelling in the legs, for example.

Urea reference values

The reference values ​​normally considered for urea are:

• For children up to 1 year old: entre 9 e 40 mg/ dL;
• For children over 1 year old: entre 11 e 38 mg/ dL;
• For adults: entre 13 e 43 mg/ dL.

However, it is important to remember that urea values ​​may vary depending on the laboratory and technique used.

Preparing for the urea test

To perform the urea test, it is not necessary to fast or carry out any other special preparation.

How the exam is carried out

The urea test is carried out by collecting a small amount of blood, which is sent to the laboratory for analysis.

High urea: what it means

The increased amount of urea in the blood may indicate that there is a large production of urea by the liver or that the kidneys are not functioning properly.

The main causes of high urea are:

• Renal insufficiency;
• Decreased blood flow to the kidneys;
• Severe burns;
• Dehydration;
• Protein-rich diet.

In case of high urea, it is always important to consult a doctor to identify the cause and initiate appropriate treatment, which may include increased fluid intake, changes in diet, use of medication and even dialysis, which is normally indicated in cases more serious.

When urea is high as a result of dehydration, for example, it is recommended to increase fluid intake. If urea increases due to diet, it is recommended to adjust the diet, preferably with the help of a nutritionist, to know the most recommended foods and which ones to avoid, without running the risk of nutritional deficiencies.

Low urea: what it means

The decrease in the amount of urea is normally not a concern, and may occur due to:

• Lack of protein in the diet;
• Malnutrition;
• Pregnancy;
• Low intestinal absorption;
• Hyperhydration;
• Inability of the liver to metabolize protein, as in liver failure or cirrhosis.

Despite being uncommon and not associated with severity, it is important that the urea value is always assessed by a doctor.