If a drug test shows positive for THC level 287, how frequently is this person using marijuana?

We drug tested our teenager and got a positive level of 287. She says she has only used it once or twice but this amount seems high. Is there any way to know how frequently someone has used marijuana based on this level?

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  • Bill C
    Lv 6
    1 decade ago
    Favorite Answer

    According to federal guidelines, the cutoff level for an immunoassay test is 50ng/ml, and for a GC/MS it is 15ng/ml.

    The differences are because th immunoassay test is an accumulation of all thc metabolites in the system, while the GC/MS test is only looking for one specific metabolite.

    In either case, although not for certain, 287ng/ml would suggest more than occasional or casual usage.

  • 1 decade ago

    not really, she could have used it recently. do regular checks and see what happens. remember, it can stay in the system for some time

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