text: how fast can a blood test detect if someone has hiv after being infected?   it can range from 2 weeks to 3 months (standard window period for hiv) depending on the person, everyone is different and all of our bodies are different... look for signs - swollen lymphs in the neck, underarms and groin areas.  also do not be fooled, a blood test can come back much sooner than our healthcare workers like to lead on... since i work in the field i can tell you that often the results can come back frmo the lab in 24 hours, depending on what lab it is sent too.