Demi Lovato has thanked her friends for helping her through her ''darkest moments''.

The 'Cool for the Summer' hitmaker has taken to Instagram to praise her pals, Sirah and Matthew Scott Montgomery for sticking by her through her recent struggles, which included a hospital stay after a drug overdose in July last year.

Sharing a snap from their holiday in Bora Bora, she wrote: ''#ThreeCourseMeal ... just me and my best friends living our best lives .. Thank you for never leaving me in my darkest moments, for always drying my tears ... even when they're from watching Moana .. thank you for being loyal, honest and so grateful for every little thing .. like crying because we swam with fish/sharks/stingray and coral reef.

''I'm so lucky to be best friends with two incredible souls who are so talented and creative because it inspires me daily. And you're so supportive of me and every little thing I do .. You've traveled across the country to visit me and stayed with me at my house for days on end when I'm struggling to make sure I'm okay but most importantly you never abandoned me like others did when I was going through s**t .. you were there to listen, without judgement and only love and I can never fully express what that means to me. You're the greatest friends I've EVER had and our future together is so bright. I love you both more than you can imagine!! (sic)''

And the 26-year-old singer previously revealed she is ''sober and grateful to be alive'' following her overdose.

She explained at the time: ''If I feel like the world needs to know something, I will tell them MYSELF ... I am sober and grateful to be alive and taking care of ME. Someday I'll tell the world what exactly happened, why it happened and what my life is like today.. but until I'm ready to share that with people please stop prying and making up s**t that you know nothing about. I still need space and time to heal.''