As soon as the MRO certifies a positive test, they will attempt to make contact with the donor. Depending on the reason and who done the test, the time frames vary. Once contact has been made he/she will ask some questions to ascertain if there is a valid reason for the positive test. If his final decision is drug
use, your employer will be contacted that same day. If you are employed in a safety sensitive position, you can no longer work in that position. And most likely will have to be evaluated my an accredited SAP(substance abuse and prevention) officer, then follow his recommendations before you can ever return to that position with any employer.
That's just a touch of what could happen. If you would not mind giving a little more info I might be able to be more particular as to what might happen. Need to know why the test was given and Type of employement/job. You can message me if you want.
Is there a reason why you may fail? if you were to fail and feel that you shouldn't have. There is a 72 hr window to request that your sample be retested.