Blood drug tests are not common forms of drug testing. If you are asked to take a blood drug test, the best way to detox and prepare is drinking lots of plain water and perspiring. If you are someone with high toxin levels or a THC (marijuana) user, go on a serious regimen of detoxification before your test. Toxins are stored in the fatty tissues of the skin. Drinking water and sweating is the only way to get clean or lower your drug metabolite count making it easier to contain whatever toxins are left. How fast you get clean depends on your fatty tissue count, speed of your metabolism, strength and amount of toxins ingested, and for how long the toxins were ingested.