Demi Lovato posted a heartfelt tribute on her Instagram Stories after her good friend Thomas died late Tuesday from a suspected overdose.
Lovato has admitted to struggling with substance abuse in the past.
"Please hold your loved ones tight. Tell them they are special and that you love them," she wrote, sharing a black and white photo of her late friend.
She then cautioned fans that "Addiction is NO joke" and called it a "terrible disease."
The 27-year-old also encouraged fans to watch out for their friends and family.
"If you or someone you know is struggling please know it's okay to ask for help," she added.
Lovato suffered a suspected overdose last summer, almost a month after revealing she relapsed after six years of sobriety.
She addressed fans a month later by writing, "What I’ve learned is that this illness is not something that disappears or fades with time. It is something I must continue to overcome and have not done yet."