Guides

CD4 and viral load: two essential blood tests

Your CD4 and viral load are the main blood tests after you are diagnosed.

After starting ART, the viral load is more important.

This is to make sure ART is working well.

CD4 count

The CD4 count tells you about your immune system.

So your first CD4 count gives an idea of how HIV has affected you so far.

  • Results are given as cells per cubic millimetre (cells/mm3).
  • The range for HIV negative adults is from about 400 to 1600. Above 500 is considered normal.
  • Even with a very low CD4 count, ART can boost your immune system much higher.
  • The CD4 percentage (CD4%) is also good to know in case your CD4 count has unexpected changes. The normal range is from about 25 to 60% with the average about 40%.
  • After starting ART, the CD4 count is tested much less often. Some clinics no longer test the CD4 count on treatment, once it gets above 500. The viral load test is then much more important.

Viral load

Viral load is the main test once you are on ART.

  • This test shows how much virus is in a small sample of blood. Results are given as copies of the virus per millilitre (copies/mL).
  • It also shows how well ART is working. The aim is to reduce this to less than 50 copies/mL. This is called undetectable.
  • If viral load doesn’t become undetectable within 1 to 3 months – or if it increases later – you might need to change treatment. This is because the drugs might not be working or you may not be taking them correctly.
  • Although an undetectable viral load shows how little HIV is in your body, you will still test positive on an HIV test. This is because HIV tests look for an immune response rather than HIV.

Last updated: 1 September 2024.