TORONTO -- While cannabis is not even tested for out of competition, UFC vice-president Jeff Novitzky says it's a constant topic of conversation in his world.

UFC fighters want to know when they should stop using it before their fights to ensure they don't exceed the limit allowed when it is tested for around their bout.

"It's probably the most-asked question that I get among our roster of fighters," said Novitzky, a former federal agent for the U.S. Food and Drug Administration who is now the UFC's vice-president of athlete health and performance. "'If I'm a regular user of marijuana, how long do I discontinue (use) before my competition to ensure I'm under the (allowed) 150 nanograms (per millilitre)?"'

"And that is one of the toughest questions I have to answer. I really don't have a good answer for anybody because each individual varies in terms of how they metabolize things in our systems."

The U.S. Anti-Doping Agency, which serves as the UFC's anti-doping partner, follows the World Anti-Doping Agency's code.

As such cannabis is prohibited only in competition, which means from noon on weigh-in day (typically the day before the fight) to immediately following the bout. That is the only time that marijuana is tested for.

During that time, it is prohibited over a certain amount of THC (the active ingredient in cannabis) -- 150 nanograms per millilitre in a urine test. The reason for that is cannabis traces can remain in the system.

It is banned during competition out of concern it might allow fighters to take more damage. It could also be a hindrance to their performance.

"Both of those conditions would only be applicable if the marijuana was used pretty close to a fight -- you're still experiencing the effects of using it," Novitzky said.

Novitzky's advice to most mixed martial arts fighters is, to be on the safe side, discontinue using marijuana a month before the bout.

Several years ago, the threshold used by WADA and most athletic commissions was much lower -- 15 nanograms per millilitre under the WADA code. That was changed so athletes weren't punished for using the drug well in advance, when it doesn't have any impact in their performance.

As of Jan. 1, cannabidiol or CBD -- which unlike the THC component of marijuana does not have any psychoactive effects -- was no longer prohibited.

CBD can be used for pain management.

"I'd say the overwhelming majority of our fighters use it. (They) express to me that they get great benefits from it," said Novitzky.

He said some early studies have suggested that CBD could also be beneficial to someone who has suffered a traumatic brain injury, if used in high doses right after the injury.

But complicating matters for UFC fighters is the fact that some countries or athletic commissions -- like Illinois and Michigan in the U.S. -- have tougher standards when it comes to marijuana use.

Novitzky says some fighters elect not to compete in such jurisdictions because of those rules. In Canada, he says most of the commissions leave drug-testing to UFC/USADA.

The UFC executive says he is not a proponent of fighters using any kind of drug, saying "the natural way" is the way to go.

"That being said, I'm also aware that our fighters do suffer from certain conditions, be it pain, inflammation, anxiety for a fight coming up, inability to sleep. Having come from the law enforcement world and investigating a lot of cases regarding prescription drugs, I'm aware of what the side effects are for a lot of these drugs out there -- sleep aids, obviously opiates for pain control. Even over-the-counter stuff that can combat inflammation is processed through the liver and kidney.

"Everything I know about marijuana and CBD can treat a lot many of those issues without a lot of those side effects."

Novitzky says the legalization of cannabis in Canada will not impact anti-doping rules governing the drug, noting that there are many substances that can be legally obtained but are banned due to performance-enhancing or health and safety issues.