Nick Diaz tested positive for marijuana metabolites at UFC 143 and is widely assumed to be facing a long suspension – but that may not necessarily be the case.

Fighters Only learned today that there is a certain tolerance on the part of athletic commissions for marijuana metabolites in an athlete’s system – it is not a strict requirement that there be no trace of marijuana use at all.

The Nevada State Athletic Commission, like most others in the US, actually allows 50 nanograms of THC metabolites per millilitre of urine sample. This is a similar level used by many other bodies which test for marijuana use but do not have a zero-tolerance policy.

Some years ago, some athletic commissions had a 100ng limit in place but it was discovered that his limit could be cheated by the testee drinking excessive water and bringing the level of metabolites in the urine below that 100 ng/mL level.

According to a US laboratory which Fighters Only contacted, and which regularly provides testing for corporations which are drug-testing employees and potential recruits, “anything below 100 ng/ml is relatively low and would broadly indicate either light general use or heavy use in the two or three days prior to the sample being provided.”

“Levels between 100 and 250 ng/ml generally indicate moderate use while anything from 250 to 750 ng/ml would classify as high and probably indicates ongoing heavy use or use within the last three days. If the level exceeds 750 ng/ml they are very high and would indicate very recent use indeed.”

Fighters Only asked the Nevada State Athletic Commission if any information was available on the ng/mL numbers that Diaz posted in his UFC 143 drug test. The answer, delivered by email, was a flat “no”. Diaz now has to respond to the allegation before NSAC will schedule a hearing, likely to take place in April.

The half-life of THC – the psychoactive element in marijuana – varies between strains and from person to person depending on dosage and method of use. But in general terms it can be said to be around three days and so levels will half in the urine every two to three days after use.

Levels should be below 100 ng/ml quite soon but lower levels (under 50 ng/ml) can persist for some time. It is apparently not unusual to find levels of between 20 and 50 ng/ml chronic heavy users for as long as three months after ceasing use.

It is generally accepted in the testing industry that prolonged exposure to marijuana smoke in an enclosed environment – eg a sealed vehicle for several hours – could produce a level of up to 30 ng/ml. But it is also widely accepted that individuals are extremely unlikely to tolerate the kind of conditions that would lead to such levels of passive intake.

A marijuana advocate and card-carrying member of the fraternity which advocates its use as a medicine, Diaz is unlikely to play coy when asked if he smokes. He has gone on the record many times to say that he does. Instead the issue now centres around what the ng/ml level of his sample was, and whether that can be determined to indicate use that was ‘recent’ to the Carlos Condit fight.

If he has posted 50ng/ml or under, Diaz is likely to be in the clear and will escape a suspension, as the usage will be determined to have been effectively ‘off season’. For comparative purposes, his 2007 positive test in Nevada was a level of 175ng/ml and was decreed to have indicated recent use.