Basically four types of drug tests exist.
Urine drug test
This procedure usually involves you going to the bathroom and filling up a cup with your urine. They either use a test card on the spot for immediate results or send it away to a lab for testing by means of a sophisticated gas analyzer.
Hair Follicle drug test
Hair testing is quite accurate and can go back up to 6 months, showing all of the toxins you used in a sort of timeline. Many people try to get around this by just shaving their head. Know that they will go for your underarm, pubic, leg or arm hair if you do not have the required 1/2 inch on your head.
Blood drug test
Blood testing is usually performed for serious employment positions or when you are applying for insurance policies. This is expensive and not very common.
Saliva drug test
This is not common and can only detect toxins used 3-4 days prior. This method is most often used by insurance companies and law enforcement agencies.