The former Sonny With A Chance star - who sought treatment for "emotional and physical issues" last year - said that it was her time in rehab which allowed her to be diagnosed.
"I never found out until I went into treatment that I was bipolar," she told People. "[But I] battled depression from a very young age."
"Looking back it makes sense. There were times when I was so manic, I was writing seven songs in one night and I'd be up until 5:30 in the morning."
However, she insisted that her time in rehab has allowed her to regain control over her life and emotions and said that she now wants to focus her energies on helping those in similar situations.
Bipolar disorder brings about unusual changes in mood and energy that can result in manic episodes - an overly excitable state - or depressive episodes - a state of heightened sadness.
Lovato recently applauded Catherine Zeta-Jones for her "brave" decision to share her struggle with bipolar II disorder.