WBC Count : Principle, Procedure and Calculation

WBC (White Blood Cell) Count: Purpose, Procedure, and Results

WBC diluting fluid is used to perform the WBC(leucocyte) count or white blood cell count

Principle of WBC Diluting Fluid

WBC diluting fluid is used to perform the WBC( leucocyte) count.

The blood specimen is diluted 1:20 (20:380 in some laboratories) in a White blood cell pipette with the diluting fluid, and the cells are counted under the low power of the microscope using a counting chamber.The number of cells in undiluted blood is reported per cumm( μl) of the whole blood.

Composition of WBC Diluting Fluid

IngredientsGrams or Mass
Glacial acetic acid 2.00 ml
Gentian Violet (1% w/v) 1.00 gm
Distilled water97.00 ml
Final pH ( at 25°C)2.2±0.2

Appearance of WBC Diluting Fluid

It is a clear solution having a purple colour

Turk solution
Turk solution

How to Count White blood cells using WBC diluting fluid

  1. Draw the EDTA anticoagulated blood to 0.5 mark on the capillary end of the WBC pipette.
  2. Carefully wipe excess blood outside the pipette using cotton.
  3. Draw the diluting fluid up to 11 marks.
  4. Mix the contents in a pipette and after 5 minutes, discard a few drops, fill the counting chamber and allow the cells to settle for 2- 3 minutes.
  5. Focus on 1 of the ” W” marked areas( each with 16 small squares) by turning the objective to 10X low power
  6. Count cells marked in all 4 ” W” corner squares.

How to count and calculate White blood cells

Number of WBCs/cumm(µl)of whole blood =No. of WBCs counted X Dilution /Area counted X Depth of fluid where,Dilution=20; Area counted= 4x1sq.mm=4sq.mm ; Depth =0.1mm(constant)

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No.of leucocytes / cu mm(µl) of whole blood = No.of cells counted X 20 / 4 X 0.1

WBC Normal range

AgeNormal White blood cell Count  range(cell/cumm of blood)
At Birth10.000 – 25000
Infant8000 – 15000
4-7 years6000 – 15000
8 – 18 years 4500 – 13500
Adult4000 – 10.000
Pregnancy12000 – 15000


  • Textbook of Medical Laboratory Technology; Praful B. Godkar

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About the Author: Arthur Westmann

DEFFE ARTHUR (AMOEBAMANN) is the founder and author of MLTGEEKS and MLTEXPO.He’s from Cameroon and is currently a Final year State Medical Laboratory Technician (MLT MA). Beyond lab works, he’s a passionate internet user with a keen interest in web design and blogging. Furthermore He likes traveling, hanging around with friends and social networking to do in his spare time.

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