Fans first took to social media to express their concern about his health after videos emerged of the singer struggling to pick up a microphone, slurring his words, rolling his eyes and falling over.
"You can't sit there and tell me that this is normal behaviour from Post, it's not and the man needs help before something bad happens to him," wrote one fan on Twitter.
"Whether it's alcohol or drugs, he's not using them for fun anymore, he's abusing them. it's too much now, people are worried."
Malone is currently on his third concert tour for his album Hollywood's Bleeding and his representatives have reportedly not responded to requests for comment.