Can you fail a drug test because of using ephedrine?

Absolutely! Ephedrine and it's cousin pseudoephedrine show as false positives for amphetimines in urine, sweat and hair test. However in multi-panel test such as a saliva test when the authority is testing for both amphetimine AND methamphetimine it will show as meth since is is a primary drug for making meth. It will show up as positive EVERYTIME so be careful! If you are taking a test that only test for amphetimines it will show up as positive there. Not all drug test are equal. Some only test for a broad category as amphetimines. Others separate between amphetiminies and methamphetimines.