The teenager, who has admitted to struggling with her body image in the past, posted a photograph of herself wearing swimwear on her official Twitter account.
"I've been working so hard to get healthy and fit... I can't believe I'm about to do this but I'm so excited... Here's my bikini time body!" she wrote alongside the picture.
"I never thought I'd ever feel confident enough to ever to (sic) that. I'm excited how far I've come since being completely ashamed of my body."
She continued to say: "I want any girl/guy out there who struggles with body image or confidence to know that it IS possible to find peace with yourself. It hasn't been easy, but it starts with a commitment to yourself... Your mind.. And your soul. And trust me, I'm still working at it!! Haha (sic)."
The Sonny with a Chance star previously opened up about her body image issues in the past, telling 20/20 that she developed an eating disorder after being bullied about her appearance as a child.
Lovato sought voluntary treatment for "emotional and physical issues" towards the end of last year, returning home in January.
She has since told fans that she is looking forward to returning to work.
> Demi Lovato: 'Cyber bullying is unacceptable'