Meps uses a NIDT 50 ng drug test(basically the instant ones that are just like the at home tests). They watch you piss so you cant cheat. I passed mine after 2 weeks being clean but everyones different. Your recruiter will test you before he sends you to meps. They wont send you to fail, they need you to get in. Worst case scenario, you test positive at the recruiting office and he will give you a couple more weeks to get clean.