For a brief introduction and guide to abbreviations, see Laboratory Tests: General Remarks.
Reference range, target level, or decision threshold
1000-5000/microL (1-5 Giga/L)
20%-45%
Interpretation of results
↑ Viral infections (eg, infectious mononucleosis, mumps, measles, viral hepatitis), certain bacterial infections (eg, pertussis, brucellosis, TB, syphilis), toxoplasmosis, leukemias of mature lymphocytes, lymphomas with bone marrow involvement, rheumatoid arthritis, Felty syndrome, after splenectomy, drug-induced reactions, serum sickness, trauma, surgery, acute cardiac disease
↓ Systemic connective tissue diseases, viral infections (eg, HIV, SARS-CoV-2), sepsis, TB, renal failure, liver failure, sarcoidosis, Cushing syndrome, after glucocorticoid therapy, immunosuppressive agents, chemotherapy and radiotherapy, Hodgkin lymphoma, certain congenital immunodeficiencies, after hematopoietic stem cell transplant