Originally Posted by
Fendibanks
If my urine test came back negative for marijuana & I only used 3 times last month(april) & I took my test may .. Will my hAir show up for marijuana ? Please help
Smoothy is correct. Once the metabolite of cannabis (THC-COOH) is incorporated into your hair it is there for an extended period.
Where I differ is that COOH is not readily incorporated into hair. [This is the incorporation rate (ICR), and all drugs have different ICRs.] It is generally acknowledged that COOH has the lowest ICR of all drugs. As example, cocaine has an ICR 3600X that of COOH.
As a result, one time or infrequent cannabis use is seldom detected in hair testing. More apt to be detected in urine... which you indicate was negative. But even in this regard comparisons can be misleading.
Urine testing can be negative one day and positive the next. That is because the THC metabolite stores in adipose (fatty) tissues [termed lipophilic] and releases at unpredictable intervals.
Now this low ICR in combination with the lipophilic nature of THC requires accumulation [and
it is cumulative] of systemic THC in order for a hair test to be positive. Accumulation requires repeated use.
Hair is a very poor medium (matrix) for detection of cannabis use. Very, very poor.
The answer to your question rests entirely on the facts aforecited. Not the month before but rather on history of previous use, generally in the range of 90 days.
In general terms, hair testing will detect heavy cannabis use [3-5 times per day] around 60-65% of subjects, moderate use [1-2 times weekly] under 40%, infrequent use [1-2 times weekly] very seldom and lesser amount almost never and one time use at 0%.
Reference:
1)
Musshoff & Madea, 2006 Peer reviewed
2)
Auwater, 2010 Peer reviewed
3)
Dupont, 2008 Authoritative but advisory
4)
Nakahara, 1995 Peer reviewed
5)
Huestis, 2007 or
Huestis, Gustafson Both peer reviewed. Marilyn Huestis is the most prolific researcher of cannibis (n the US NIH) for at least 2 decades.
6)
Smeal, 2007 (doctoral dissertation) Critically reviewed
7)
Musshoff, 2012 Peer reviewed
8)
Ledgerwood, et al 2008 Peer reviewed
Addition:
Hair drug testing does not involve "plucking". Pulling or extracting sub-dermal hair, in other words the follicle of the hair.
Tested hair is removed by cutting, like a hair cut, above the scalp.
Never below. Hair is not yanked from you head. Ergo it is the hair
shaft that is tested and
not the follicle. (see references above)