Guides › Changing treatment and drug resistance

What is HIV drug resistance?

Drug resistance is when a drug that would normally be active no longer works.

Resistance can develop to drugs used to treat viral, bacterial and fungal infections.

The drugs stop working because the virus (or other organism) has evolved or changed while on treatment.

The risk of resistance increases when drug levels are low. This happens if you do not take all your treatment at the correct time. See Figure 2 below.

Figure 2: Drug levels with good adherence

Graph showing drug levels staying within a band where there is less risk of side effects (high levels) and resistance (low levels).

February 2011

Decisions relating to your treatment should always be taken in consultation with your doctor. Information in this guide is intended to support those discussions.

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