Bieber's opened up on the condition, which is caused by a tick bite, ahead of the release of his 10 part documentary series on YouTube and because he's had people contacting him about how he looks.
"While a lot of people kept saying justin Bieber looks like s..., on meth etc. they failed to realize 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," Bieber said.
"These things will be explained further in a docu series I'm putting on YouTube shortly.. you can learn all that I've been battling and OVERCOMING!!"
"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" Bieber concluded.
In March last year, Bieber announced he was taking a music hiatus to focus on family and health.
The Sorry hitmaker is said to have been seeking treatment for mental health struggles in those weeks, and in a candid post on Instagram at the time, he told fans he will be taking some time away from the spotlight to put his own needs, and those of his loved ones, first.
The singer's emotional issues reportedly prompted Justin and model Hailey to postpone plans to celebrate their September courthouse wedding with a bigger party for family and friends, so he can prioritise his wellbeing.
Bieber hasn't released an album since 2015's Purpose.