Terrence Higgins Trust uses cookies to improve your experience of our websites. For more information or to change the use of cookies, please click here.

Accept and Close

HIV drug resistance


The reason why taking your HIV treatment properly (‘adherence’) is so important is because poor adherence can lead to the development of drug resistance. This can cause your anti-HIV drugs to stop working for you and you may need to change your treatment.

What is HIV drug resistance?

Resistance is a term doctors often use. It means that some HIV cells mutate and carry on reproducing despite treatment. In other words, the drugs don’t work well any more and you become resistant to them.

Every time HIV makes a new copy of itself, it ends up slightly different. Often these differences are not important but sometimes the new copy is different in a way that is ‘resistant’ to the drugs you’ve been taking. This means that it will be able to reproduce again, even when you take the drugs.

How does resistance to anti-HIV drugs develop?

Resistance can develop if you don’t take your HIV treatment as prescribed, at the right time every day (often referred to as adherence).

It's possible to have resistance to some drugs even before you start HIV treatment. You may have been infected with a strain of the virus that is already resistant to some anti-HIV drugs. The British HIV Association (BHIVA, the organisation for specialist HIV doctors in the UK) recommends that resistance tests are always carried out when you are diagnosed with HIV, before you start treatment for the first time, and before changing treatment (if your viral load is detectable) to identify whether your strain of HIV is resistant to any anti-HIV drugs.

If you're taking combination therapy, it's important to make sure that enough of the drugs are in your blood all the time so that they can do their job properly. Missed or late doses could mean there are reduced levels of the drugs in your blood. This could allow the virus to make more copies of itself, including drug-resistant copies.

What does it mean if resistance develops?

Drug-resistant HIV could lead to the treatment not working, and you not being able to use the same drug (and, sometimes, other drugs in the same class - this is called 'cross-resistance') again in the future. The next combination of drugs you are given might be more complicated to take, or cause more side-effects.

If you're able to take each dose of the combination therapy at the right time each day, then the development of drug-resistant HIV is unlikely. That means the drugs will work for many years.

What can I do if I develop resistance?

If you do develop resistance to some drugs, don’t panic – there will still be other treatment options available to you. New drugs have been developed that are effective against drug-resistant strains of HIV.

It's very important that your new combination of drugs is taken properly. If not, you may develop resistance to those too, and this could mean that your HIV becomes very hard to treat.

Next: Changing your treatment ››

‹‹ Back to: Taking your medication (adherence)



Whole Star Whole Star Whole Star /images/icons/star-half-value.gif Empty Star (4 votes cast) Please log in or register to vote. What's this?


Please log in or register to add this article to My favourites. What's this? Adding an article to My favourites will allow you to easily come back to it later or print it.

The Information Standard: Certified member

This article was last reviewed on 6/7/2017 by Anna Peters

Date due for the next review: 6/7/2020

Content Author: S. Corkery (NAM)

Current Owner: Kerri Virani

More information:

British HIV Association guidelines for the treatment of HIV-1-positive adults with antiretroviral therapy 2015 (2016 interim update), N Ahmed, B Angus, M Boffito, M Bower, D Churchill, D Dunn, S Edwards, C Emerson, S Fidler, †M Fisher, R Horne, S Khoo, C Leen, N Mackie, N Marshall, F Monteiro, M Nelson, C Orkin, A Palfreeman, S Pett, A Phillips, F Post, A Pozniak, I Reeves, C Sabin, R Trevelion, J Walsh, E Wilkins, I Williams, A Winston

Adherence, by Greta Hughson, NAM Aidsmap, June 2017

HIV drug resistance, World Health Organization, 2017

British HIV Association guidelines for the routine investigation and monitoring of adult HIV-1-positive individuals 2016, Funmi Awosusi, Gary Barker, Marta Boffito, Satyajit Das, Lucy Dorrell, Esther Dixon-Williams, Charlotte Hall, Bridie Howe, Sebastian Kalwij, Nashaba Matin, Eleni Nastouli, Frank Post, Melinda Tenant-Flowers, Erasmus Smit, Dan Wheals

What is drug resistance?, NAM Aidsmap, March 2014

The basics – drug resistance, NAM Aidsmap, January 2017

How does resistance affect treatment, NAM Aidsmap

Transmission of resistant virus, NAM Aidsmap

Taking drugs on time, NAM Aidsmap, January 2017

Reducing the risk of resistance, NAM Aidsmap, March 2014

Transmission of drug resistant HIV, NAM/Aidsmap, March 2014

When to use resistance tests, i-Base, May 2014

Viral load, by Greta Hughson, NAM Aidsmap, May 2017

Williams I et al. BHIVA guidelines for the treatment of HIV-1 positive adults with antiretroviral therapy 2012 (Updated November 2013)