Developing resistance

If HIV develops resistance to the drugs you are taking, this means that they will be unable to suppress HIV efficiently, and viral load usually begins to rise.

Keeping viral load below the level of detection is associated with a very low risk of developing resistance to the anti-HIV drugs you are taking.

This is because the chance of developing resistance when you are taking anti-HIV drugs depends on the amount of HIV which is still being produced in your body.

The lower your viral load, the lower your risk of developing resistance to the drugs you are taking.

So, suppressing viral load to undetectable levels (below 50 copies) is likely to delay the development of resistance for longer.

Cross resistance

HIV that has developed resistance to one drug that you are taking may also be resistant to some other similar drugs which you have not taken yet. This is called cross-resistance.

Cross-resistance can limit the range of drugs you can take in the future. In order to keep as many options open as possible, some doctors argue that treatment should always aim for undetectable viral load.

However, other doctors take the view that if you switch drugs every time your viral load rises above the limit of detection, you may run out of drugs relatively quickly. If it is possible to switch early with higher CD4 counts and a lower viral load, this is recommended. For more information, see another NAM booklet in this series, Resistance.