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Your CD4 count is the number of CD4 cells in a small amount of your blood (written as the number of cells per cubic millimeters, or mm3). You can have a CD4 count test.

• CD4 cells are part of your immune system, the cells that help fight infections.
• HIV destroys CD4 cells. The fewer CD4 cells you have the more damage HIV has done to your immune system.
• People who don't have HIV normally have about 1,000 CD4 cells per cubic millimeter of blood.
• As the number of cells falls you're more at risk of getting certain infections and types of cancer.¹
• Doctors use your CD4 count to help decide whether you're at risk of getting the infections and types of cancer that go along with HIV. This helps them decide what treatment you need. See Opportunistic infections and cancer for more.

Here's what your CD4 count result means.

• More than 500 cells/mm3: Your risk of getting opportunistic infections is low. But you may get some general symptoms of HIV infection, such as a fever or swollen glands.
• 200 cells/mm3 to 500 cells/mm3: You're at risk of getting pneumonia, tuberculosis, fungal infections or types of cancer of the blood cells.
• Less than 200 cells/mm3: You're at risk of getting Pneumocystis carinii pneumonia and fungal diseases. You may find it hard to keep your weight up.
• Less than 50 cells/mm3: You're at risk of getting cytomegalovirus infection and Mycobacterium avium complex infection.

To learn more, see Opportunistic infections and cancer.

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.