When HIV isn't fully controlled by anti-HIV drugs, the virus makes copies of itself at a very rapid rate. Mistakes (called mutations) can occur, creating new forms of the virus that may not be as sensitive to a particular drug as the original virus. This is called drug resistance, because the virus can multiply and cause disease even when a patient is taking the drug.

Currently, the standard treatment for HIV usually involves taking 3 powerful anti-HIV drugs every day. It is designed to reduce the amount of HIV in the body to a level that cannot be detected by standard lab tests (called "undetectable viral load"). The lower your viral load, the lower your risk of developing resistance because there's less virus to produce mutations. In the past, patients would take only 1 or 2 drugs at a time--and almost everyone developed some drug resistance. Why? Because these treatments were not powerful enough to stop the virus from making drug-resistant copies.

If your health care provider suspects that you have a drug-resistant virus, he or she can do testing (called "HIV genotyping" or "HIV phenotyping") to help identify the drugs to which your virus is resistant. The results of the testing, along with a detailed history of what medications you've taken in the past, help to determine which drugs to use in the future. There are more anti-HIV drugs available now than there used to be, so you have more options for successful treatment.

To reduce your chances of developing drug-resistant HIV:

• Work with your health care provider to find an ART combination that is effective and that you can tolerate.
• Take every dose of your medications every day, missing as few as possible.
• Keep your appointments with your HIV clinician and have your CD4 count and viral load checked every 3-4 months. That will help detect resistance before it affects too many drugs in your regimen.
• Keep a record of which combinations of HIV medications you've taken.