As part of your health exam and prior to issuance of a health or life insurance policy insurance companies usually require blood testing. These are also increasingly being used by employers as a pre-hiring screen. Law enforcement agencies use this type of test to determine the level of intoxication after an accident or arrest. Doctors and hospitals use this test to determine how various glands and organs in the body are doing their job, for cancer detection, and for other health checks.

A vial or two of blood is drawn by a nurse or lab technician and run through various procedures in the lab to determine the types of drugs being used and the level of toxicity in the body. This procedure generally takes longer to develop an answer than a saliva test or urinalysis.