Following rumours about his health, the singer took to Instagram to open up about his diagnosis.
"While a lot of people kept saying Justin Bieber looks like s--t, on meth etc," he wrote in a lengthy post.
"They failed to realise I've been recently diagnosed with Lyme disease, not only that but had a serious case of chronic mono which affected my, skin, brain function, energy, and overall health."
The 25-year-old will also be releasing a YouTube documentary that will include more details about his recent health struggles.
"It's been a rough couple years but getting the right treatment that will help treat this so far incurable disease and I will be back and better than ever NO CAP," he finishes.