Demi Lovato's younger sister has thanked the medical team who saved the star's life following her overdose last month.

Madison De La Garza, 16, took to Instagram on Monday (20.08.18) to ring in her sister's 26th birthday with a throwback snap of the pair of them as kids, where she took the time to praise those who made sure Demi survived after she was found unconscious at her home after a suspected heroin overdose.

In a lengthy caption, Madison wrote: ''today could have been one of the worst days of my life, but instead i get to spend it thanking God, the incredible doctors, demi's team, and everyone across the world who offered their support - without all of these people i wouldn't have my big sister anymore. (sic)''

Madison then went on to praise the 'Sorry Not Sorry' singer for taking care of her, and said she was ''thankful'' to be able to wish her a happy birthday.

She added: ''i've been thinking about how i wish that everyone could see the silly little things that she does, like how her nostrils move when she says certain words and when she brushes my hair behind my ear when i'm trying to sleep, because those are the things i'm thankful for today. they seem so small, but those little things make up my sister - not a singer, not a celebrity, and definitely not what she's been described as in the media - she's a daughter, a friend, and my big sister... and i am so, so thankful that i can tell her happy birthday. #happybirthdaydemi (sic)''

Demi - who celebrated six years of sobriety earlier this year, before revealing through new track 'Sober' in June that she had relapsed - is currently in rehab in order to fight her addictions, and it was recently reported she is looking for tough love whilst in the facility.

A source said: ''This is not her first rodeo. She doesn't want to feel like things are being handed to her. For Demi, this is a strength test.

''The rehab she is in is much more drill sergeant-esque. It's not nurturing. At places like Promises, you live on the beach and go horseback riding. That's not what Demi needs to put her in check.''