The blood that essentially runs through the veins, arteries, and capillaries has 55% plasma and 45% of blood cells. The blood functions in the following ways:

  • Transports oxygen and nutrients to the lungs and other organs.
  • Clots during injury to prevent blood loss.
  • Transports cells and antibodies to fight infections.
  • Carries waste to kidneys and liver to clean and filter the waste.
  • Regulate body temperature.

The blood and its components need to be in ideal reference ranges while carrying out the essential body functions. The blood is an aggregate of blood plasma and blood cells- red blood cells (RBC) or erythrocytes, white blood cells (WBC) or leukocytes, and platelets or thrombocytes. 

The DLC or the Differential Leukocyte Count measures the percentage of various WBC types in the blood. The DLC test informs about the presence of immature WBCs that lead to anomalies like anaemia, leukaemia, and infections. 

What is a DLC test?

WBCs or leukocytes are blood cells that are innate to the immune system. The differential Leukocyte test or the DLC test investigates the percent of different WBC types in the blood.

Total Leukocyte Count or the TLC test measures the total number of WBCs or leukocytes in the body. To sum up, the TLC DLC test investigates the WBC credentials in the blood. 

Why is a DLC test required?

The DLC in a blood test is done in case of one of the following conditions:

  • Measured during the Complete Blood Count (CBC) test in regular health check-ups,
  • TLC and DLC tests can be done together to diagnose the internal infection condition,
  • It can be a follow-up test in case of abnormal CBC outcomes,
  • Helps detect infections and inflammations,
  • Helps detect conditions with low WBC counts like blood disorders, and bone marrow diseases,
  • Helps keep a check on bone marrow functions,
  • Helps monitor cancer treatment and chemotherapy.

What are the different types of leukocytes measured in a DLC test?

WBCs are the type of blood cells that are produced in the bone marrow and present in the blood and lymph system. They aid the immune system fight infections. There are five major WBC types.

  • Neutrophils: The most common WBC type that helps destroy microorganisms or pathogens causing infections. 
  • Lymphocytes: Lymphocytes are distinguished into three types. B-cells, T-cells, and Natural Killer Cells. The B-cells take the help of antibodies to destroy the pathogenic viruses and bacteria in the body. T-cells destroy the body’s cells infected by pathogens or tumour cells. Natural killer cells eventually kill all the foreign cells marked by antibodies as cancer cells or infected cells by phagocytosis. 
  • Monocytes: They form a defensive system against the pathogens attacking them.
  • Eosinophils: Helps fight inflammation, infections, and allergies.
  • Basophils: Defends by producing enzymes essential to fight allergic reactions and asthma. 

Result Interpretation of the TLC, DLC Tests

The normal differential WBC counts vary depending on factors, such as age, gender, health, and external factors. WBC production in the bone marrow increases with an infection, inflammation, or cancer. The increased WBCs work together to target, fight, and treat the condition. Depending on the condition one or more WBC types remain elevated in the blood. As the condition or infection subsides, the bone marrow reduces WBC production, and the WBC count in the blood decreases. 

The Normal ranges of DLC in adults are mentioned below:

WBC Type Reference range levels in percentage
Neutrophils or Polymorphs 40 to 60%
Lymphocytes (B and T cells) 20 to 40%
Monocytes 2 to 8%
Eosinophils 1 to4%
Basophils 0.5 to 1%

Increased counts of one or more WBC types may be an indication of infection or chronic condition that needs to be addressed. Increased or decreased DLC can also indicate possibility of health conditions of the immune system, autoimmune disorders, and cancers where the body attacks its own cells of the immune system. 

The normal range of total Leukocyte count (TLC) is 4000 to 11,000 cells/ cubic millimetre of blood. The decrease in total WBC count or leukopenia results when the body’s ability to fight infections and diseases reduces, making the body vulnerable to health complications. 

This condition is generally seen when a patient is undergoing chemotherapy treatment, influenza, tuberculosis, malaria, typhoid, and dengue. 

Elevated total WBC count or TLC levels is leukocytosis. Chronically infected people- have rheumatoid arthritis, inflammations, connective tissue disorders, blood disorders, leukaemia, or newborn infants. 

The TLC-DLC test does not diagnose a particular condition but work as important indicators when the body is having an infection, inflammation, or an acute condition. A TLC-DLC test may require follow-up tests or further investigations to point to a particular condition or direct towards a treatment. 

Frequently Asked Questions

  • What is the normal range of DLC?

The DLC blood test normal range are:

  • Neutrophils – 2500-8000 per mm3 (55-70%)
  • Lymphocytes – 1000-4000 per mm3 (20–40%)
  • Monocytes – 100-700 per mm3 (2–8%)
  • Eosinophils – 50-500 per mm3 (1–4%)
  • Basophils – 25-100 per mm3 (0.5-1%) 
  • What happens when DLC is high?

When the blood DLC test shows high results, the diagnosis may be a probable infection, inflammation, cancer, or any other condition the body is fighting against. 

  • Are the DLC and WBC the same?

White blood cells (WBC) or leukocytes are the type of blood cells that aid the defensive immune system against infectious pathogens or foreign bodies. Differential Leukocyte count is the percent of different leukocytes or WBCs in the blood.  


WBCs are components of the blood cells that fight out an infection, inflammation, or chronic condition in the body. With five different WBC types present in the blood, the DLC or the differential blood count test gives a percentage measure of each white blood cell (WBC) type and also helps disclose the abnormal conditions of the body, showing reduced immunity. TLC, or total leukocyte count, gives the overall measure of WBCs in the blood. 

An early or regular TLC- DLC testing allows early detection of any acute condition, enabling early treatment and prognosis. 

Ms. Srujana is Managing Editor of Cogito137, one of India’s leading student-run science communication magazines. I have been working in scientific and medical writing and editing since 2018. I am also associated with the quality assurance team of scientific journal editing. I am majoring in Chemistry with a minor in Biology at IISER Kolkata.

Leave a Reply

Your email address will not be published.