What Are Lymphocytes in a Blood Test?

Q: What Are Lymphocytes in a Blood Test?

Lymphocytes explained: normal range 1,000-4,800/µL (20-40% of WBC), what high lymphocytes (viral infection, leukemia) and low lymphocytes (HIV, steroids) mean.

Lymphocytes are white blood cells central to your adaptive immune system. They include T-cells, B-cells, and natural killer cells.

Normal Range

Absolute: 1,000–4,800/µL
Percentage: 20–40%

High Lymphocytes (Lymphocytosis)

Viral infection — mononucleosis (EBV), CMV, hepatitis
Chronic lymphocytic leukemia (CLL) — marked elevation in older adults
Acute lymphoblastic leukemia (ALL) — common in children
Smoking — mild chronic elevation

Low Lymphocytes (Lymphopenia)

HIV/AIDS — destroys CD4+ T-cells
Corticosteroids — prednisone
Chemotherapy and radiation
Severe acute infection
Autoimmune disease
Malnutrition
Kidney failure

CD4 Count

A specific lymphocyte subset used to monitor HIV and define stage of immunosuppression

Source: NLM MedlinePlus, American Association for Clinical Chemistry.

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