Is it a possibility that I could get a doctor to draw blood and find out about my biological parents via DNA?

-I do not know my biological parents and have been itching to know them for the past 20 years (21 years tomorrow). I just want to know.Unless your biological parents had committed a crime, or their DNA was on thr database for some other reason, there would be no way to find them through you DNA. Even if it was on record, it would be hard to convince the police to go through their archives for you.
DNA is done via a mouth swab, not blood.................and unless your parents DNA is on record, so unless they are criminals, then no as there is no one to 'match' your DNA to..........