Depends on quantity consumed, the drug in question and the type of test conducted.

Some drugs dont show up in the Armed Forces drug screening. Cant say here as that would be innappropriate, but not all drugs tests are foolproof as Rabs case has proved.

As in his case a urine test was failed yet a blood test was passed. Certain drugs can also be detected in hair samples.

I was going to offer advice to RAB but he got a good result so its not needed, but I failed a drug test once because I was given ephedrine (legitimately by medical staff) to open my nasal passages for pressurised training and that shows up as an illegal substance. there was no trace of ephidrine in my medical records due to an admin fuck up, so i was in deep shit for a while until the exact person who administered it could be contacted and comfirm what happened.

Bloody good job he remembered me as well, as the SETT when busy can get loads of people through for training in a short period and id be well pissed off if my career was fucked due to somebodies forgetfulness!!!!