Known as lymphocytopenia, decreased lymphocyte levels may indicate:

- An autoimmune disorder like lupus

- Bone marrow damage (e.g., chemotherapy, radiation treatment)

- An infection like HIV or hepatitis

- A severe infection, such as sepsis, which is wiping out white blood cells faster than the body an make them

Lymphocytes are a subtype of white blood cells in the body and part of your immune system that works to fight off infections.

A higher-than-normal amount of lymphocytes is called Lymphocytosis.

Lymphocytosis is a condition that often results from your immune system working to fight off an infection or other disease. There is an increase in white blood cells with this condition. 

Many underlying medical conditions can cause lymphocytosis.

Though it cannot be prevented, lymphocytosis can be treated by caring for the underlying cause.

Lymphocytosis is very common. It’s especially common in people who have:

- Had a recent infection (most commonly viral)
- A medical condition that causes long-lasting inflammation, like arthritis
- A reaction to a new medication
- Severe medical illness, such as trauma
- Had their spleen removed
- Certain types of cancer, like leukemia or lymphomaHigh lymphocyte blood levels indicate your body is dealing with an infection or other inflammatory condition. Most often, a temporarily high lymphocyte count is a normal effect of your body’s immune system working. Sometimes, lymphocyte levels are elevated because of a serious condition, like leukemia.

Doctors treat lymphocytosis by working to resolve its underlying cause. For most people, lymphocytosis goes away as the underlying condition improves. Your doctor can order specific diagnostic tests to help pinpoint the cause of your lymphocytosis. These tests may include other laboratory tests to rule out infections or tests examining other body tissues, like bone marrow biopsy and looking at your blood under a microscope.

Lymphocytosis tells your doctor that you have or have had an infection or illness. In many cases, lymphocytosis simply means your body has been fighting a viral infection.

In some cases, lymphocytosis is one of the first signs of certain blood cancers, including chronic lymphocytic leukemia (CLL), which is the most common type of leukemia seen in adults. Further tests are usually necessary to rule out other medical conditions and make a firm diagnosis of the cause of lymphocytosis.