The CD4 count is a measure of the health of your body’s Immune system. Usually, an adult’s CD4 count is anywhere between 500 and 1200 cells per cubic millimetre of blood, with women having naturally slightly higher counts than men.

When you are infected with HIV, it takes over some of your CD4 cells and uses them to produce more HIV. This reduces the total number of CD4 cells available to fight other Infections.

Monitoring CD4 Counts
Even while someone with HIV feels well, millions of CD4 cells are being invaded and destroyed by HIV daily and millions more are being produced to replace them. Over a number of years, the CD4 count usually declines. A CD4 count of between 500 and 200 indicates that damage has been done to your immune system. A CD4 count of below 200 means that you are at risk from serious infections such as PCP (a form of pneumonia), and a count below 100 means that you are at risk from other life threatening infections, e.g. Toxoplasmosis. If your CD4 count falls below certain levels you should be offered prophylaxis (preventative medicine) against opportunistic infections.

Your CD4 count can be regularly monitored by means of a simple blood test. The count can go up and down in response to infections, Stress, exercise and the time of day, but it is of primary importance in indicating how your health is holding-up under the assault of HIV.

Your CD4 cell count is very important in the decision regarding when HIV treatment should start, with treatment being considered when the CD4 count falls below 350.