A CD4 count is a blood test used to measure the number of CD4 cells—important white blood cells that help regulate the immune system. This test is primarily used to assess the health of the immune system in individuals with HIV (human immunodeficiency virus), which targets and destroys these cells, potentially leading to compromised immune function and progression to AIDS (acquired immunodeficiency syndrome). AIDS is characterized by a significantly low CD4 count, making individuals more vulnerable to opportunistic infections and certain cancers.

For people living with HIV, regular CD4 counts are crucial for monitoring the impact of HIV on the immune system, adjusting treatment to prevent infections, and assessing the effectiveness of HIV medications in conjunction with viral load tests. Additionally, CD4 counts can assist in diagnosing AIDS, post-organ transplant monitoring, identifying types of lymphoma, and diagnosing DiGeorge Syndrome, a genetic disorder linked to immune deficiencies.

To perform a CD4 count, a healthcare professional draws blood from a vein in your arm. No special preparation is needed, and the procedure is quick and relatively painless, with minimal risks such as temporary pain or bruising at the needle insertion site.

Results are reported as cells per cubic millimeter of blood, with normal ranges typically between 500 and 1,200 cells per cubic millimeter for healthy adults and teens. A count below 500 indicates immunosuppression, while a count below 200 suggests AIDS. Adherence to prescribed HIV medications can help manage the virus, improve CD4 counts, and support overall health. Regular testing is essential for effective HIV management and treatment.