Blood Drug Testing

In a routine blood test, is it likely (or even possible) for the lab to detect drug usage?

I have to get bloodwork done soon to check my thyroid function and fun stuff like that. I have no history of being caught with drugs or anything, so there is no reason anyone would drug test me. However, is there a chance the lab people would notice the THC or whatever in my system without actually testing for it? Or is there any chance they would test it for some reason anyway? I'm doubting it, just making sure.

Public Comments

1. If they actually test for THC metallobites in your blood, yes. If it's just a simple thyroid checkup, they have no reason to test for drugs. Plus, you can never be forced to take a drug test without your consent (exceptions are your job, but you make a signature agreeing to take a drug test anyway and emergency situations when you come in to the ER ODed on something).
2. They might as the drugs maybe affecting whatever they are testing you for...be careful, and if you are on drugs, get the hell off them!
3. No, the Laboratory will only test for the specific things that the physician requested and nothing more than that...ever. In the United States, all Laboratory testing is carried out upon the execution of a physician's order. Under rare circumstances, the laboratory will have "reflex" tests that are ordered if a test is abnormal. These are approved by the hospital's medical staff and the Laboratory's Medical Director. For example, if your thyroid testing was abnormal (usually a Free T4 and TSH), a particular laboratory might have a policy in place, that stated that additional thyroid testing would automatically be performed. These policies are usually put in place to save the physician the aggravation of having to call the laboratory and request the additional testing every single time he has an abnormal test of a specific kind. Secondly, drugs of abuse testing is seldom performed on blood, and more so on urine, because drugs are metabolized and excreted in the urine. This is the fluid of choice for the vast majority of drug testing for this reason.