The HIV virus is highly adaptive. This means it changes itself to survive better within its host. HIV replicates very quickly— so quickly it often makes mistakes when it copies itself. Some of these mistakes, or mutations, are beneficial to the virus. Through natural selection, the virus starts purposely including these beneficial mutations when it copies itself. This ultimately results in a new strain—or variation—of the virus. The new strain can make the HIV virus less reactive to the medications you’re taking, which is known as drug resistance. HIV drug resistance can be difficult to treat, so make sure you’re informed about this serious problem. 1. Drug resistance results when HIV mutates itself. In the case of drug resistance, the virus can keep replicating despite the presence of the drug. The strains of the virus without the mutation tend to die off, while the strain with the mutation thrives. Once drug resistance develops, it isn’t reversible and it can cause your treatment to fail. 2. Poor medication adherence is the main cause of drug resistance. Not taking every medicine correctly every day—or poor medication adherence—is the main cause of drug resistance. HIV drugs slow the replication of the virus, but they can’t stop it completely. Skipping a dose gives the HIV virus the chance to multiply faster and possibly develop a drug-resistant mutation. That’s why it’s so important to be ready for the commitment of HIV treatment when you start therapy. 3. You can transmit drug-resistant HIV to someone else. Once you have a drug-resistant strain of HIV in your blood, it’s possible to transmit it to someone else. It’s also possible for you to get a drug-resistant virus from someone else. In either case, this is called transmitted drug resistance. If a person gets a drug-resistant strain, treating it with that specific drug will not work. So it’s important to know what type of virus you have—drug resistant or “wild type.” A wild type has no drug-resistant mutations. 4. Your doctor can test for drug resistance. As soon as you know you have HIV, your doctor should order drug-resistance testing. It’s a blood test that can show if the virus has transmitted drug resistance. This will help your doctor choose your first HIV regimen. You should have drug-resistance testing even if you plan to delay HIV treatment. Your doctor should repeat the testing whenever you decide it’s time to start treatment. Your doctor may also order testing if it looks like your HIV regimen is failing. It will help with selecting a new regimen. 5. Drug resistance can apply to an entire class of HIV medicines. When HIV develops resistance to one drug in a class of HIV medicines, it is sometimes resistant to other drugs in the same class. This is called cross-resistance. It can mean some HIV drugs won’t work for you even if you’ve never taken them. Cross-resistance can limit your drug choices for future HIV regimens. 6. You can reduce the risk of drug resistance. The good news is you can take steps to decrease the risk of drug resistance. The single most important thing you can do is to take your HIV medicines exactly as directed every single day. HIV regimens involve multiple drugs with different schedules, storage requirements, and food restrictions. This requires a high level of commitment. Here are some tips for success: Work closely with your doctor to find a regimen that will work for you. Be honest about what you can commit to and what you can’t. You’ll do more harm than good by trying to stick with a regimen that doesn’t work for your lifestyle and habits. Once you start a regimen, take every dose every day. Pill organizers and online dose reminders can help you stay on track. Talk with your provider and ask for help if you’re struggling with your regimen. It may be time for a change. Keep all of your appointments, including lab tests to check your CD4 count and viral load. This can allow your doctor to identify early on if your treatment is losing effectiveness. Keep your own records of your HIV regimen combinations. 7. You may still have options if drug resistance develops. Salvage therapy refers to treatment when HIV becomes resistant to the three main classes of HIV medicines. Salvage therapy is not as effective and usually can’t suppress viral load to low levels. But it’s possible to stay healthy on salvage therapy. If HIV becomes resistant to most or all HIV drugs, it may be time to consider participating in a clinical trial. Through a clinical trial, you can get access to drugs that aren’t FDA approved yet.