Drug tests - how do they work and what do they detect?

Do you suspect that someone put a drug in your drink? Or maybe your child is behaving in a suspicious way and you want to check if he is under the influence of drugs? You can buy drug tests to detect drugs such as THC (marijuana and hashish), amphetamines and methamphetamine, ecstasy, cocaine and opiates (morphine, codeine, heroin) at a pharmacy without a prescription and then do them yourself at home.