The 24-year-old rap star recently sparked concern among fans after he was seen tripping, stumbling, and writhing on-stage - but he played down fears during a gig at the FedExForum in Memphis, Tennessee, on Friday (06.03.20).
He told the audience: "I'm not on drugs. I feel the best I've ever f***ing felt in my life. And that's why I can bust my ass for these shows and f***ing fall on the floor and do all that fun s**t.
"But for anybody that's concerned here, I appreciate the love and the support, but I feel f***ing fantastic and I'm not doing drugs."
Adam DeGross, Post's tour photographer, has also discussed the rapper's recent on-stage behaviour.
He wrote on Instagram: "This has been one of the most fun tours we've been on. No one does drugs, no one is going nuts, everything is all good.
"He legit blew his nose during the space ghost Bigfoot video, which there's like 40 Minutes more footage of. We just pass the time by making funny videos. (sic)"
He added: "The stage is made of grates, so you can see the light shine up, he caught his foot, and played it off. Then he always makes those faces during 'Rockstar' has done it for the last 100 shows."
Meanwhile, Post recently said his facial tattoos come "from a place of insecurity".
The 'Better Now' hitmaker explained: "I'm a ugly-a** motherf***er.
"It does maybe come from a place of insecurity, to where I don't like how I look, so I'm going to put something cool on there so I can look at myself and say, 'You look cool, kid,' and have a modicum of self-confidence when it comes to my appearance."