In comparison to a urinalysis drug test .
The detection of marijuana is currently less sensitive than the other drugs in identifying low level drug users, but is considered approximately equal to urinalysis in identifying marijuana users.
The detection period for hair is limited only by the length of the hair sample and is approximately 90 days for a standard screen.
If his hair is really short he might not get the best results.
His level should not go up but should steadily go down if he is not using.
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