CD4 and viral load: two essential blood tests

Your CD4 and viral load are the main blood tests used to monitor HIV.

CD4 count

  • The CD4 count tells you about your immune system. Results are given as cells per cubic millimetre (cells/mm3).
  • The range for HIV negative adults is from about 400 to 1600. Getting 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%.

Viral load (VL)

  • The VL test shows how much virus is in a small sample of blood. Results are given as copies of the virus per millilitre (copies/mL).
  • VL tests show how well ART is working. The aim is to reduce this to less than 50 copies/mL. This is called undetectable.
  • If VL 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.

Last updated: 1 October 2019.