If a person changes their HIV drug therapy, how long would it take for the individual to know if her or she is "drug resistant" to the new regimen? And, what would the signs be?

After a change to a new regimen, we expect a prompt fall of one half log in the first month, and of one log or more in the virus load after 6 months.

For this reason, guidelines recommend that clinicians monitor the viral load after 4 weeks of therapy, in order to demonstrate that an adequate response has been achieved. Viral loads are then repeated regularly, usually every 2-3 months, or as needed, as determined by the doctor.

In most cases, the patient will be unaware of whether optimal control has been achieved or not.

One exception is patients who have become symptomatic due to uncontrolled HIV viremia, for example with fever, night sweats, weight loss, skin rash, or other manifestations. Such patients have complete or partial relief of their symptoms when they resume effective ART.

If a patient does not have the optimal response to ART, and the virus load never becomes undetectable, i.e. < 50 copies/ml, and continues to rise above 1,000, this may a sign of drug resistance, and a repeat viral load and resistance test should be performed. Failure to achieve a viral load < 50 copies/ml can also be a sign of poor adherence, i.e. that the patient is not taking their medications as prescribed, so at the same time a resistance test is performed, renewed efforts to achieve the best possible drug adherence should be undertaken.