Hard to say: Typically, a hair test goes back 90 days, but it depends on how fast your hair grows. They are looking at 1 1/2 inches of hair, closest to the scalp. Incidentally, you should not avoid it by shaving your head. They would just use some other hair. And if they do, it is pretty obvious that you are trying to hide something.
Answered 5/4/2018
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