Comedian, Heather McDonald Clip of her passing out during routine, talks about vaccination,

# Here's the moment Heather McDonald suddenly collapsed in the middle of her comedy set

The comedian just addressed the moment she fainted on stage during a sold-out show in Tempe, AZ ... sharing talking about the incident Tuesday on her podcast, "Juicy Scoop."

As you can see, Heather is just finishing up a joke when she collapses to the floor.

Heather says she's still not sure why it happened ... though she says she didn't eat before her weekend set and only drank half a Red Bull and some water. Heather also shot down rumors someone might have spiked her drink.