I took a half tab of phentermine and then was givin a drug test 2 days after. was the only time i had taken the drug the whole month. will it show up?

Probably Not: Most drug tests do not test for phentermine, this assumes you are using prescription phentermine obtained from your doctor, buying what is labelled "phentermine" on the internet is another story, many contain amphetamines which will test positive lesson learned: be careful what you put into your body! real Phentermine is inexpensive & can be obtained from any weight loss doc.