Ariana Grande [Photo: Courtesy]

Ariana Grande has worried her family after she 'broke down on stage' while singing a tribute to late rapper Mac Miller.

It has been nine months since Miller tragically died at the age of 26, from a fatal drug overdose.

He was romantically involved with Ariana, though they had split up by the time he died but it still hits the 25-year-old singer hard, and she once again shed a tear for him during a performance in Pittsburgh, Mac's hometown.

Ariana paid tribute to Mac in the lyrics of her hit single Thank U, Next and she plays a medley of his music before her live shows.

On Wednesday night it was the first time that Ariana had sang the song in Pittsburgh and the enormity of this personal moment wasn't lost on the singer.

During the performance, her emotions got the better of her and Ariana fell silent as she found herself unable to sing the line "wish I could say, 'Thank you' to Malcolm" (which was Mac Miller's real first name).

Mac Miller dated Ariana before his death (Image: Getty Images)

As she choked back tears, the crowd looked to lift Ariana and cheered encouragement to the singer, as her backing singers continued with the main vocal duties.

It was a difficult night for Ariana as she was overcome with emotion during the opening number, Raindrops (An Angel Cried).

The grieving singer had requested that an empty seat was reserved for Mac in one of the nearest rows to the stage.

Sources close to Ariana have told Radar Online that her family are becoming concerned about her wellbeing, as she has had a few breakdowns with her emotions in recent times.

They said: "Of course her family is worried. She has so many things on her plate and she has been trying to juggle everything while trying to also have some semblance of a personal life.

“Ariana has been so hot and cold lately and no one knows which version of her they are going to get and right now she is more unpredictable than ever.”