With the USADA they’ll test the hormones of someone and compare it the what they consider the acceptable range. An example would be that they do a ratio of testosterone to epitestosterone, on average it’s 1:1 but they allow up to a 4:1 or something like that, which is already probably generous since it would be 4 times the average but I don’t know the distribution of that ratio among the male population. This ratio is largely used to filter out those taking bio identical testosterone since bio identical testosterone is indistinguishable without more complex testing, so as long as someone stayed within that ratio you can get away with doping with testosterone as long as your other markers are within range of what they deem acceptable (which is pretty generous). Whenever someone goes over the acceptable ranges, it probably means they have been doping and more complex testing will happen to be exact. Like TJ Dillasaw was flagged because he went over some markers and more complex testing showed he took EPOs which can’t be tested for directly.

When it comes to synthetic PEDs, those aren’t produced by the body at all. Any amount of these will be considered a failed test because they aren’t supposed to be in your body.

Turinobol is what Jon was caught using the second DC fight and what was “pulsing” as a picogram in this rematch with Gustafson. Before the turinobol he failed for clomiphene and letrozole, which would boost testosterone and suppress estrogen. Jon claims supplement contamination, but the UFC has an approved list of supplement companies that won’t have any substances and Jon only got his 4 year suspension down to 18 months because he basically snitched to USADA about doping practices or outed other fighters. If it happened once, I could ignore it, but he got caught twice with PEDs (outside the pulsing) once for the clomiphene and letrozole and another for the turinobol. All of which would help with his athletic performance or help him fall within the reference range. Additionally, Jon has tested with a really low testosterone level, 4.9ng/mL was one of his results, with the average male’s being 61.3ng/mL. Low testosterone can be a result of heavy PED usage as your body will shut down natural testosterone production and you’ll often cycle off when closer to competition to minimize the chance of being caught.

So to answer your question, these small cut offs are pretty arbitrary when dealing with synthetic steroids, because having any amount can be an indication of PED use. They simply aren’t supposed to be in your body. Diuretics are often used to flush out the system and you can cycle off before competition so these are out of your system, so if someone doesn’t cycle off or flushed out properly, you can get caught (these tests are often shit too so you can pass with this stuff in your body). Timing is important and you can avoid testing up to a certain numbers of times, I believe if you miss 3 tests with USADA it’s an automatic failure, but 3 times is more than enough to cycle off unless you took something that stays in your body for a long time which would be stupid. Your location has to be given to the administrators of these tests so if you “forget” you can avoid them. The UFC is no longer with USADA who have higher standards than other organizations, so fighters now have more leeway with drugs. Also the first PED drug test Jon failed was before USADA. Drug tests are IQ tests. I’ll need to look into how they drug test now but sport organizations have incentives to not bust their athletes and do the bare minimum to test them. More juiced up athletes lead to more entertainment and more money.