The singer performed a set at iHeartRadio's release party for her new album Tell Me You Love Me in New York on Saturday night. She struggled while singing "Stone Cold," her voice cracking as she tried to hit a high note.
"F--k," she said, smiling.
"I don't know what to do," she said, then continued singing, drawing cheers.
She later joked to event host and Z100 radio personality Elvis Duran, "That's what we call not lip-syncing."
The concert was streamed live online by iHeartRadio. Lovato got onstage at 7 p.m. She wore a baggy orange long sleeve shirt and matching shirts and thigh-high boots, held up by suspenders. She also looked like she was feeling a bit under the weather. She told Duran that her voice was not at "100 percent."
The venue was packed with her fans, who sang along to her songs.
"Even when I lose my voice on stage my fans know how to keep me from being down.. thank you my Lovatics I love you," Lovato tweeted.