Is my biggest risk that aids will develop after taking blood?

Need clarification: I want to be sure i understand your question. The process of drawing blood for a laboratory does not give you a risk of acquiring hiv, the virus which causes aids. Getting a HIV blood test, lets you know if you have hiv, and i teach that "knowledge is power" in this regard. If you are asking if you can aquire HIV after you have a negative test, you can. Get retested!