Two bloods tests are of crucial importance in monitoring HIV. These are CD4 cell counts (to monitor your immune system) and HIV viral load tests (to monitor the levels of virus in the blood). The booklet Viral Load and CD4 in this series provides more information on these tests.

CD4 cell counts tend to be higher in women than men in people who are not infected with HIV.

Your CD4 cell count may go up or down with your menstrual cycle. The oral contraceptive pill may also lower your CD4 cell count, but not to such an extent that your health may be at risk. Pregnancy can lower your CD4 cell count too; this is due to the effect of having a larger blood volume when pregnant and after the baby is born, the CD4 count usually goes back to the same level as before.

Your viral load may be lower than a man's shortly after you are first infected with HIV, but this does not have any effect on the speed of HIV progression.