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Urea Test Procedure

A Urea test is used to determine how well your kidneys are working. It does this by measuring the amount of urea nitrogen in the blood. Urea is a waste product that’s created in the liver when the body breaks down proteins. Normally, the kidneys filter out this waste, and urinating removes it from the body.

Urea Test Procedure

Urea levels tend to increase when the kidneys or liver are damaged. Having too much urea nitrogen in the blood can be a sign of kidney or liver problems.


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Panel Tests: Urea, Blood Urea Nitrogen, Creatinine, Calcium, Phosphorus, Albumin, Magnesium, Total Protein, Electrolytes

Test Procedure:

Berthelot Method

Test Principle:

Urease hydrolyzes urea to ammonia and Co. The ammonia formed 2 further reacts with a phenolic chromogen and hypochlorite to form a green coloured complex. Intensity of the colour formed is directly proportional to the amount of urea present in the sample.

Kit Components:

  • Reagent 1 : Urea Enzyme Reagent
  • Reagent 2 : Urea Chromogen Reagent
  • Reagent 3 : Urea Standard 40 mg/dl

Reagent Preparation

Bring all the reagents to Room Temperature.
Working reagent – Dissolve the enzyme reagent (Reagent 1) in Deionised water as per volume indicated on the vial.
Reagent 2 – is ready to use

Sample Preparation:

  • Serum: No Need any Preparation
  • Urine: Dilute urine 1 + 49 with distelled water.
Method Endpoint, Berthelot method
Wavelength 600 nm (600-630 nm)
SampleSerum, heparin plasma, urine
Linearity upto 200 mg/dl
Sensitivity The lower limit of detection is 10 mg/dL


Bring reagents and samples to room temperature.
Pipette into clean dry test tube labeled as Blank (B), Standard (S) and Test (T):

Addition Sequence Blank (B)Std/Cal (S)Sample (T)
R1 (Working Reagent) 1 ml 1 ml 1 ml
Sample0.01ml (10 µl )
Standard/Calibrator 0.01ml (10 µl )
Mix well and Incubate at 37°C For 5 min.
R2 ( Chromogen Reagent ) 1 ml 1 ml 1 ml
Mix well and incubate for 5 minutes at 37°C. Measure the absorbance of Standard (Abs.S) and Test (Abs.T) against reagent blank at 600 nm within 60 minutes.

CALCULATION (light path 1 cm)

Urea Calculation


  • Serum/Plasma =10 – 50 mg/dl
  • Urine = 15 – 30 gm/24 hrs

Calculation of Urea Nitrogen:

BUN = Urea/2.14 = mg/dl


  • Serum: 7 to 20 mg/dL
  • Urine: 12 to 20 g /24 hours

Related Articles:

Possible References Used

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