Even with decades of scientific research in HIV, a major challenge faced by people with HIV (PWH) continues to be HIV drug resistance.

HIV can change or mutate over time, and HIV can develop something called a resistance mutation. When this happens, some HIV treatments may not work as well. Sometimes, HIV can already have a resistance mutation when it’s transmitted, or it can develop while someone is on treatment. But taking HIV treatment as your doctor prescribes can help lower the risk of resistance.

A major goal of HIV treatment is to become undetectable, which means there is so little virus in the blood that a lab test can’t measure it. Current research shows that taking HIV treatment as prescribed and getting to and staying undetectable prevents HIV from spreading through sex. This is also called U=U, or “Undetectable equals Untransmittable.” Reaching an undetectable viral load is a critical milestone for many people living with HIV, and by starting and staying on treatment, they can live longer and healthier lives with HIV as a chronic, manageable condition.

But here’s the challenge: treatment resistance can still stand in the way of getting to and staying undetectable, especially for those who have had to stop or restart care.

In the US in 2022, only about 65% of PWH were virally suppressed, which means having less than 200 copies of HIV per milliliter of blood. For those who do not stay on treatment — sometimes because of stigma and life challenges — the risk of resistance and illness increases. Resistance can mean the virus no longer responds to certain medicines, making treatment harder.

As a clinician and researcher, I’ve seen how resistance can affect how well some treatments work. In the early years of HIV treatment, resistance emerged as a major concern, influencing the decisions doctors made and shaping community conversations. Resistance isn’t talked about as much today, but that doesn’t mean it has gone away. Resistance is an especially real risk for people who experience care gaps, have trouble taking medicine regularly, or need to restart treatment. However, most people with HIV face some risk of developing resistance.

That’s why it’s so important to talk with your healthcare provider about what resistance means and why taking your medicine as prescribed makes such a difference. That’s why reengaging people in care must go hand-in-hand with clear, supportive conversations about resistance, and making sure each person has access to medicines that fit their unique health needs. The good news is that science continues to evolve. Today, there are multiple treatment options available for PWH who have resistance, giving people more treatment options when restarting care. Your healthcare provider can help guide you to the option that’s right for you.