Urea in the blood

Urea in the blood . The urea test is an analysis that is performed separately or on a general request for a biochemist in the blood. It measures the amount (concentration) of urea or urea nitrogen present in the blood.

Urea is the end result of protein metabolism. It is formed in the liver from the destruction of proteins. During digestion proteins are separated into amino acids, these contain nitrogen that is released as ammonium ion, and the rest of the molecule is used to generate energy in cells and tissues.

Ammonium binds to small molecules to produce urea, which appears in the blood and is excreted in the urine. If the kidney does not work well, urea accumulates in the blood and its concentration rises.


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  • 1 Denomination
  • 2 What is this study for?
  • 3 Technique of realization
  • 4 Problems and possible risks
  • 5 Normal blood urea values
  • 6 Assessment of abnormal results
    • 1 Elevated blood urea (uremia) may appear in:
    • 2 Decreased urea may appear in:
  • 7 Source


  • Urea
  • Blood urea nitrogen.

What is this study for?

In general it is a parameter that indicates kidney function, although it may be altered in liver diseases or dehydration.

Technique of realization

To perform this analysis it is not necessary to be fasting. The taking can be done in an appropriate place (consultation, clinic, hospital) but sometimes it is done in the patient’s own home.

  • To perform the taking, it is necessary to locate an appropriate vein and in general the veins located in the elbow flexion are used. The person in charge of taking the sample will use sanitary gloves, a needle (with a syringe or extraction tube).
  • You will put a tortor (rubber-latex tape) on your arm so that your veins retain more blood and appear more visible and accessible.
  • You will clean the puncture area with an antiseptic and by palpation will locate the appropriate vein and access it with the needle. They will release the torture.
  • When the blood flows through the needle, the healthcare provider will aspirate (using the syringe or applying a vacuum tube).
  • At the end of the shot, the needle is removed and the area is pressed with a cotton swab or similar to promote coagulation and you will be instructed to flex the arm and keep the area pressed with a plaster for a few hours.

Problems and possible risks

  • Obtaining a puncture of the vein may cause some pain.
  • Possible difficulty in finding the appropriate vein can lead to several punctures
  • Appearance of a bruise (bruise or cardinal) in the extraction area, is usually due to the fact that the vein has not closed well after subsequent pressure and blood has continued to flow, causing this problem. A Hirudoido or Thrombocide type ointment can be applied to the area.
  • Inflammation of the vein (phlebitis), sometimes the vein is disturbed, either for a purely physical cause or because it has become infected. The area should be kept relaxed for a few days and a Hirudoido or Thrombocide type ointment can be applied to the area. If the problem persists or fever appears, you should consult your doctor.

Normal blood urea values

Normal values ​​in adults are between 7 and 20 mg per deciliter. Values ​​of 5 to 18 mg / dl are accepted in young children. The highest values ​​of 100 mg / dl are due to significant kidney failure.

Assessment of abnormal results

High blood urea (uremia) may appear in:

  • Diets with excess protein
  • Kidney disease
  • Heart failure
  • Gastrointestinal bleeding
  • Hypovolemia (burns, dehydration)
  • Starvation,
  • Kidney obstructions (stones, tumors).

Decreased urea may appear in:

  • Low protein diet.
  • Liver failure.
  • Pregnancy.
  • Excess hydration.
  • Malnutrition


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