Lymphocytes
White blood cells made up of B and T cells, measured in the blood differential
Also known as
Definition
Lymphocytes are one of the five main types of white blood cells. They mainly include B cells and T cells: B cells fight invading viruses, bacteria and toxins, while certain T cells can destroy the body's own cells that are infected with viruses or have become cancer cells. Lymphocytes are measured in the blood differential, as a share of all white blood cells and often also as an absolute count.
| Parameter | Value |
|---|---|
| Unit | % of white blood cells; absolute count as /nl (= 10⁹/l) |
| Reference Range | About 20–40% of white blood cells in adults (example normal range from the German hematology society DGHO). Some labs use their own ranges and also report absolute counts; the reference range on your own report is what counts. Discuss any deviation with your doctor. |
Agree on your personal target range with your doctor.
↓ What a low value means
A low lymphocyte value (lymphopenia) can be linked to conditions that affect the production of white blood cells, such as bone marrow diseases or HIV, to chemotherapy or to certain medicines. The percentage also drops arithmetically when another type of white blood cell rises sharply. That is why the value is always read together with the rest of the blood count. Discuss the result with your doctor.
↑ What a high value means
Lymphocytes mainly target viruses, so a high value (lymphocytosis) can be linked to a viral infection. Unusual differential results can also be linked to autoimmune or inflammatory diseases, leukemia or other cancers. An unusual value alone is not a diagnosis; further tests often follow. Discuss the result with your doctor.
When to test
Lymphocytes are measured in the blood differential, for example during routine checkups, to look into symptoms or an unusual white blood cell count, and to monitor known blood disorders. No special preparation is needed. Mention your medicines, as some can affect the white blood count.
Frequently asked questions
Why does my report show lymphocytes as a percentage and as an absolute count? +
The percentage shows their share of all white blood cells, while the absolute count shows the amount per volume of blood. If another type of white blood cell rises sharply, the lymphocyte percentage can fall even though their absolute count stays the same.
What is the difference between B cells and T cells? +
B cells act against invading viruses, bacteria and toxins. Certain T cells can attack the body's own cells that are infected with viruses or have become cancer cells. Both groups count as lymphocytes.
Do I need to fast for a blood differential? +
No, no special preparation is needed. The sample is taken from a vein in your arm like any other blood draw.
Should a slightly unusual lymphocyte value worry me? +
Unusual values do not always mean a condition that needs treatment. Doctors interpret them together with symptoms, medical history and other blood results; discuss your result with your doctor.
Lymphocytes
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.