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Diagnostic Tests 2023

Urea test: what is it for and why it can be high

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Urea test: what is it for and why it can be high
Urea test: what is it for and why it can be high

The urea test is one of the blood tests ordered by the doctor that aims to check the amount of urea in the blood to know if the kidneys and liver are working properly.

Urea is a substance produced by the liver as a result of the metabolism of proteins from food. After metabolism, urea circulating in the blood is filtered by the kidneys and eliminated in the urine. However, when there are liver or kidney problems, or when you have a very high protein diet, the amount of urea circulating in the blood increases, characterizing uremia, which is toxic to the body. Know how to identify the symptoms of uremia.

Most of the time, the urea test is requested along with other tests, especially creatinine, because this way it is possible to better assess the functioning of the kidneys for blood filtration.


Urea test reference values

The urea test values may vary according to the laboratory and technique used for the dosage, however the reference values normally considered are:

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

To perform the urea test, it is not necessary to be fasting or perform any other preparation, and the test is done from the collection of a small amount of blood, which is sent to the laboratory for analysis.

What does the exam result mean

The result of the urea test must be evaluated by the doctor who requested the test along with other tests that have been requested, and the result is considered normal when within the reference values.

1. High urea

Increased concentration of urea in the blood may indicate that there is a large amount of urea being metabolized by the liver or that the kidneys are not working properly, with a change in the blood filtration process. Some situations that can lead to increased blood urea are:

  • Kidney failure;
  • Decreased blood flow to the kidneys, which may be due to Congestive Heart Failure and Infarction, for example;
  • Severe burns;
  • Dehydration;
  • High-protein diet.

For this reason it is important to identify the disease and start the appropriate treatment, and the use of medication may be indicated to control pressure and the amount of urine or dialysis, which is usually indicated in the most severe cases when other parameters are also present. changed.

When increased urea is a consequence of dehydration, for example, it is recommended to increase the intake of plenty of fluids during the day, as it is possible to normalize the levels of urea in the blood. In the case of increased urea due to food, it is recommended to adjust the diet, preferably with the help of a nutritionist, so that it is possible to know the most suitable foods without running the risk of having nutritional deficiencies.

2. Low urea

The decrease in the amount of urea in the blood is usually not a cause for concern, and may occur due to lack of protein in the diet, malnutrition, pregnancy, low absorption from the intestine or the liver's inability to metabolize protein, as in liver failure.

When the exam is indicated

The urea test is requested by the doctor with the aim of evaluating the function of the kidneys and monitoring the response to treatment and the evolution of kidney diseases. The test may also be requested when the person has symptoms of uremia or kidney problems, such as excessive tiredness, urinary problems, increased blood pressure, foamy or bloody urine, or swelling of the legs, for example.

Thus, in addition to requesting the urea dosage, the dosage of creatinine, sodium, potassium and calcium can also be recommended. In addition, a 24-hour urine test may be indicated, the collection of which should begin after the blood is collected for the test, to check the amount of urea released in the urine. Understand how the 24-hour urine test works.

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