LOS ANGELES -- There's been a common theme in recent months when news has emerged about potential violations of the UFC's anti-doping policy, administered by USADA: Fighters who are flagged claim they didn't know they were taking something that was on the banned substance list.

The unregulated supplement industry is usually at the center of these situations. Yoel Romero recently had a potential two-year violation suspension negotiated down to six months, while Lyoto Machida just last week self-reported using an obscure ingredient on USADA's banned list.

For his part, UFC flyweight champion Demetrious Johnson said it's a chore just keeping up with what is and isn't legal.

"They're so strict, you just don't know," said Johnson, who defends his title against Henry Cejudo on Saturday in the co-main event of UFC 197. "I don't know what's on the banned substance list. Someone said they're adding new stuff on here."

Johnson's solution? He gives a USADA rep a call every time he's going to use something, even if it's something as simple as Tylenol.

"I think the biggest thing with USADA is, I don't know the logistics of the Lyoto thing, but, like, that's why I truly do not, if I take something ... if I take Tylenol and ibuprofen, I call USADA. I say ‘Hey, I'm taking ibuprofen bro, is that okay?'"

Ultimately, Johnson agrees with the idea a fighter is ultimately responsible for what they put in their body, whether or not the banned substances list is cumbersome.

"Absolutely," Johnson said. "That's why I don't take proteins supplements."