Justin Bieber has been battling Lyme disease.

The 25-year-old singer revealed on Instagram that he has been suffering from the infectious disease - which is spread by ticks - and said he would be explaining his battle further in his upcoming YouTube documentary series, 'Justin Bieber: Seasons'.

Justin also claimed to have fought off "a serious case of chronic mono", and said he was working hard to "overcome" his ailments.

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Sharing a screenshot of a story posted by TMZ that broke the news about his Lyme disease diagnosis, he wrote: "While a lot of people kept saying justin Bieber looks like s***, on meth etc. 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. 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 (sic)"

In the 10-part documentary series - which premieres on January 27 - the 'Love Yourself' singer will talk about the symptoms he endured in 2019, which he says went undiagnosed until late last year.

According to the report by TMZ, Justin battled extreme depression because he was suffering and no one knew what was wrong with him.

The publication also reports that before Justin was diagnosed, he was given medicine that caused his skin to break out, which has since cleared up.

The 'Sorry' hitmaker is now reportedly on proper medicine and says he is physically and mentally ready for his upcoming album release and tour.