I have a question about giving blood. At the recent blood drive, they said that they would test my blood for HIV. I also remember hearing that you can be infected for three months without it showing up on a blood test. So my question was do they wait for three months before testing donated blood for HIV, or can they test it right away? Does the fact that you can't tell you contracted HIV for 3 months mean that they can't detect the actual virus, but they just test for your T-cells?

I checked with the Puget Sound Blood Bank to answer your question. They do Nucleic Acid Amplification Testing on all blood units and the window is 6-8 days from exposure as well as HIV antigen testing and the HIV antibody testing with a window  of 2 weeks from exposure. So there is pretty thorough screening of all blood donations which would pick up HIV infection from about one week after exposure.