5. They give you limited information. Most drugs clear the system pretty quickly, says Levy, so parents would have a tough time catching a child's occasional use.
6. And they can be costly. A package of home tests can be pricier than a visit to a medical professional. Manlove paid roughly $50 for a six pack of urine tests, though costs vary widely.
7. You're a parent, not the police. Some experts worry that the practice of home drug testing may damage the parent-child bond. "I'm not sure that's the relationship that parents want to have with their kids," says Rogers, who himself is the parent of a former teenage drug abuser (who's now a sober 21-year-old). "They shouldn't be policemen, just parents."