Chelsea Lately alum Heather McDonald fractured skull after collapsing during standup show

Heather McDonald, a comedienne and former writer on Chelsea Lately, sustained a skull fracture after she collapsed on stage during a standup comedy show in Arizona Saturday night.

McDonald's rep confirmed to PEOPLE that the comic, 51, fainted about three minutes into her set, which started at 7 p.m. at Tempe Improv in Tempe, Ariz. She was then "admitted to a local hospital where a comprehensive work up [was] under way."

McDonald shared updates in the emergency room to her Instagram followers via Instagram Stories.

"I passed out onstage. I got up, I did one joke and I felt so dizzy," she said.

"I cannot believe this happened," she later added. "I feel so terrible that they had to tell everyone to leave and then cancel the second show. Tempe, I will be back. I've never ever fainted in my life."

McDonald had just performed at Tempe Improv the night before and posted a photo from that night on her social media. Her rep also told PEOPLE, "Thus far the tests have revealed no underlying medical issues that may have precipitated this event."

Some members of the audience spoke with TMZ about the event and said McDonald fainted after doing a bit on being "vaxxed, double vaxxed, boosted," which had led some of them to believe the fainting was part of the routine.

TMZ reported that an EMT and nurse, who were in the audience, went on stage to provide first aid. McDonald later told the outlet she declined an ambulance and had her sister-in-law drive her to the hospital.

EW reached out to McDonald's rep for further comment.

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