If you are a former drug addict and working through recovery, voluntarily administer yourself drug tests on a monthly basis at a local drug testing center

This will create a paper trail that proves you have been clean for as long as you claim you have.
My brother is currently in this position. He got clean in 2012, but his hospital admissions records were visible in his permanent medical history. His initial application for a medical certification was rejected by the FAA. When he appealed, the FAA inquired about proof of his current sobriety. Since he had no paper record of his sobriety, he had to start taking drug tests voluntarily to prove he is sober.

The point is that as far as an employer or government agency is concerned, you are only sober for as long as you can prove you are. Your word isn't going to mean anything to these people. If you claim to have been sober for X period of time, the only way to prove it is to have a paper trail of regular drug tests performed by a certified lab testing service. Despite finishing his rehab program in 2012, my brother can only prove he has been clean for 9 months.

He pays about $65 per test and does it through Lab Corp in case anyone is wondering.
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LPT :: Life Pro Tips