Total Leucocyte Count (TLC) Test – Range, Process, All Details
Verified by: Dr. Shreyas Cadabam
The total leucocyte count (TLC) test checks the number of white blood cells (WBCs) in your blood. It helps detect infections, immune deficiencies, and inflammation.
Doctors often use TLC as a first-line investigation to assess immune response and determine whether further diagnostic testing or treatment is required.
What is a Total Leucocyte Count (TLC)?
TLC refers to the total number of white blood cells in a blood sample. These cells defend against infections.
A change in your total leucocyte count can reflect how your immune system is functioning and whether there’s an underlying illness requiring attention.
Why is the TLC Test Done?
Doctors recommend the total leucocyte count test in various situations, such as when you show signs of infection, inflammation, or fatigue. It is also used to:
- Monitor chronic illness
- Assess immune status before/after treatment
- Guide recovery progress
- Identify conditions like leukaemia
It helps in early detection and medical decision-making.
Normal Range of Total Leucocyte Count
The TLC normal range for adults is 4,000–11,000 cells/µL. In children, the range is higher, from 5,000–13,000 cells/µL. Elderly people tend to fall on the lower end.
Readings above or below these thresholds may suggest infection, immune deficiency, or inflammation. When lymphocytes are low, it could indicate viral infections or bone marrow issues.
How is the TLC Test Performed?
A blood sample is drawn from a vein, usually in the arm. It’s sent to a lab where automated machines or manual microscopy calculate the total leucocyte count.
The process is quick, safe, and doesn’t need fasting. Inform your doctor about any medication. Hygiene and sterile tools ensure minimal risk of infection or discomfort.
Causes of High Total Leucocyte Count (Leukocytosis)
High TLC levels, or leukocytosis, occur due to infection, inflammation, or blood-related conditions. Elevated total leucocyte count may also result from physical stress, steroid use, or cancers like leukaemia.
Infections
Bacterial, viral, or fungal infections can cause a sharp increase in white blood cells. The body produces more WBCs to fight the infection, leading to a higher total leucocyte count. Common examples include pneumonia, tuberculosis, urinary tract infections, and skin abscesses.
Inflammatory Conditions
Chronic inflammation caused by conditions like rheumatoid arthritis, lupus, or inflammatory bowel disease often increases WBC levels.
These autoimmune disorders stimulate continuous immune activity, leading to a raised total leucocyte count even in the absence of active infection.
Stress and Medications
Physical trauma, surgery, or emotional stress can lead to higher TLC. Medications such as corticosteroids stimulate WBC production.
In such cases, a raised total leucocyte count doesn’t signal disease but reflects the body’s stress response or pharmacological effect.
Leukaemia and Blood Disorders
Leukaemia and other blood cancers result in uncontrolled production of white blood cells, raising the total leucocyte count abnormally.
These are usually immature or abnormal cells that don’t function properly, leading to immune dysfunction and other health complications.
Causes of Low Total Leucocyte Count (Leukopenia)
A low total leucocyte count, or leukopenia, can signal bone marrow suppression, viral infections, or autoimmune conditions.
It is often observed in patients undergoing chemotherapy or those with advanced viral illnesses.
Viral Infections
Viral infections such as dengue, HIV, hepatitis, and measles can lead to a significant drop in white blood cells. These infections impair the bone marrow's ability to produce WBCs, often resulting in lymphocytes low in the blood, which compromises the immune system’s ability to respond effectively.
Bone Marrow Disorders
Diseases like aplastic anaemia, lymphoma, or the effects of chemotherapy and radiation can suppress bone marrow activity.
This leads to reduced WBC production and a lower total leucocyte count, weakening immune function and increasing the risk of infection and disease progression.
Autoimmune and Deficiency Conditions
Conditions such as systemic lupus, Hashimoto’s thyroiditis, and severe vitamin B12 or folate deficiencies affect the production and survival of white blood cells.
These may present as lymphocytes low on blood tests and result in a consistently low total leucocyte count, requiring medical investigation.
What Conditions Can Affect TLC Levels?
TLC levels are influenced by infection, immune disorders, medications, and stress. Changes in total leucocyte count offer early clues into many illnesses, helping clinicians determine the need for further testing.
Bacterial & Viral Infections
Most TLC abnormalities are due to infections. Bacterial infections tend to raise TLC, while some viruses may lower it. Monitoring total leucocyte count helps track disease progress and recovery.
In viral infections like dengue or HIV, lymphocytes may be low, indicating compromised immunity or delayed immune response that needs close medical monitoring.
Autoimmune & Inflammatory Diseases
Diseases like rheumatoid arthritis, lupus, and ulcerative colitis trigger immune activation or suppression. Inflammatory responses can raise or lower the total leucocyte count, depending on disease activity.
These conditions are more common in older adults and women, and abnormal TLC levels are often used to monitor treatment efficacy or flare-ups.
Cancer, Chemo, Radiation
Cancer and its treatments have a profound effect on blood cells. Chemotherapy and radiation may suppress bone marrow, leading to a lower total leucocyte count. Some cancers, especially leukaemia's, increase immature WBCs.
Monitoring TLC during treatment helps adjust dosage, track side effects, and prevent serious infections caused by neutropenia or lymphocytes low conditions.
Interpreting TLC in Children and the Elderly
Age significantly impacts the interpretation of total leucocyte count results. Children typically have higher baseline values, while elderly patients may show mild changes even during serious illness, requiring careful clinical judgement.
Paediatric TLC Ranges
Children normally have higher TLC values due to their developing immune systems. A reading of 5,000–13,000 cells/µL is typical.
A high total leucocyte count in children may not always signal infection but must be considered along with symptoms and overall clinical presentation.
TLC in Elderly Patients
Older adults may not exhibit elevated TLC even during infections. Their immune systems often respond differently.
A mild deviation in total leucocyte count can still indicate a significant health issue, so results should be interpreted in the context of symptoms and medical history.
TLC Test vs Differential Leucocyte Count (DLC)
While total leucocyte count shows overall WBC levels, DLC breaks down cell types like neutrophils and lymphocytes.
Both tests together offer a more comprehensive view of immune function and disease status.
TLC vs Total WBC Count
The terms total leucocyte count and total WBC count are often used interchangeably. However, TLC more precisely refers to the overall number of white blood cells per microlitre.
It serves as a starting point in many diagnostic panels and helps identify trends before other specific markers are tested.
TLC vs DLC
TLC offers a summary count, while DLC analyses types of WBCs. A low TLC with lymphocytes low may suggest viral infection or immunosuppression.
Combining both tests provides detailed insights into the immune system’s condition, particularly in chronic illness, cancer monitoring, and infection assessment.
How to Prepare for a TLC Test
No fasting is required for the total leucocyte count test. However, inform your doctor about current medications, as steroids and antibiotics may alter results.
Stay well-hydrated, rest adequately before the test, and avoid heavy exercise just prior to sample collection for the most accurate reading.
Limitations of the TLC Test
The total leucocyte count is not diagnostic on its own. It gives a general picture of immune activity but must be interpreted with symptoms and other tests. TLC variations can occur due to temporary stress, dehydration, or recent infections, so clinical correlation is essential for accurate conclusions.
What to Discuss with Your Doctor Post-Test
Discuss what your TLC result means and whether it reflects an ongoing issue. Ask if further testing is needed, especially if lymphocytes are low or counts are high.
Your doctor may recommend treatment, lifestyle changes, or monitoring to address infections, autoimmune activity, or bone marrow problems.
Conclusion
The total leucocyte count test is a key marker of immune health. It helps detect hidden illnesses and guides clinical decisions.
Always consult a healthcare provider to interpret results accurately and understand their relevance to your symptoms and medical history.
How can Cadabam’s Diagnostics help you?
Cadabam’s Diagnostics offers fast, accurate TLC testing using advanced technology. Our expert team ensures timely results and personalised consultations, helping you understand your immune status and next steps. Trust Cadabam’s for reliable, patient-centred care and diagnostic excellence.