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Absolute Lymphocyte Count (ALC)

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An Absolute Lymphocyte Count (ALC) test measures the number of lymphocytes, a type of white blood cell, in the blood. This test is a key indicator of infections, autoimmune disorders, immunodeficiency syndromes, stress, etc. It is often done as part of a complete blood count test that also measures other types of blood cells.

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Understanding Absolute Lymphocyte Count (ALC)

Lymphocytes are produced in the bone marrow and help the immune system fight against infections and certain diseases. These cells are an important part of the immune system response, and changes in their numbers tell valuable information about an individual's immune system health.

An Absolute Lymphocyte Count (ALC) (ALC) test helps detect and monitor infections, such as tuberculosis, hepatitis, etc. It can be used to evaluate other immune system disorders, such as autoimmune diseases, immunodeficiency disorders, and lymphoproliferative disorders. Additionally, this test monitors the effectiveness of cancer treatments, such as chemotherapy or radiotherapy, and detects their potential side effects.

A low ALC, also known as lymphocytopenia, indicates a decreased number of lymphocytes in the blood that is suggestive of several conditions, such as viral infections, bacterial infections, autoimmune disorders, bone marrow disorders, etc. Generally, lymphocytopenia increases the risk of infections and affects the body’s ability to fight them off. On the other hand, a high ALC, also known as lymphocytosis, indicates an increased number of lymphocytes in the blood that is suggestive of conditions like certain viral and bacterial infections, leukemia, lymphoma, autoimmune disorders, chronic inflammatory disorders, etc. The specific symptoms and complications of low and high ALCs usually depend on the underlying causes. No special preparation is required for an ALC test; eat or drink as per your daily routine.

Test result ranges are approximate and may differ slightly between different labs depending on the methodology and laboratory guidelines. Talk to your doctor about your specific test results. The results will help them determine your medical condition and formulate your overall treatment plan.

What does Absolute Lymphocyte Count (ALC) measure?

An Absolute Lymphocyte Count (ALC) test measures the total number of lymphocytes in the blood. Lymphocytes are a type of white blood cells that play an important role in your immune system and help your body fight disease and infection. There are two main types of lymphocytes:

T lymphocytes (T cells): T cells control your body’s immune system response and directly attack and kill infected cells and tumor cells.
B lymphocytes (B cells): B cells make antibodies. Antibodies are proteins that target viruses, bacteria, and other foreign pathogens.

Lymphocytes help your immune system remember every antigen (a foreign substance) it comes in contact with. After an encounter, some lymphocytes turn into memory cells. When these memory cells run into an antigen again, they recognize it and quickly respond. It is also the reason why getting vaccinated helps prevent certain diseases.

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FAQs related to Absolute Lymphocyte Count (ALC)

Why is an ALC test important?

An ALC test is an important marker of the functioning of your immune system. Changes in lymphocyte count can indicate a wide range of health conditions, such as infections, autoimmune disorders, immunodeficiency syndromes, etc.

How is an ALC test done?

An ALC test is done using a sample of blood that is withdrawn from a patient’s vein. The blood sample is collected in a vial and sent to the lab for analysis.

Do I need to fast before taking an ALC test?

No fasting is required for this test. You can schedule it at your convenience without avoiding food or water beforehand.

Is there any risk associated with an ALC test?

There is no risk associated with this test. However, as a needle is used to prick and take out your blood sample, you may experience bleeding, swelling, or blood collection under the skin, which is usually self-limiting. If these symptoms do not recede, consult your doctor.

What does a high lymphocyte count mean?

A high lymphocyte count may indicate the presence of an infection or other significant illnesses.

What does a low lymphocyte count mean?

A low lymphocyte count may indicate that your immune system is working at a suboptimal level.

Content created by

Dr. Swati Gupta (Anand)

MD Lab Medicine, MBBS

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Last Updated

20th Oct 2025