WARNING: This is tough to watch ...
UFC fighter Julija Stoliarenko collapsed TWICE on Friday while trying to weigh-in for her fight ... and was ultimately taken away on a stretcher.
27-year-old Stoliarenko (9-4-2) was supposed to take on Julia Avila (8-2) at UFC on ESPN 21 on Saturday night in Las Vegas.
Stoliarenko had to cut weight down to 135 pounds for the fight -- and she didn't show up to the scale until there were less than 15 minutes left in her official weigh-in window, according to MMA Junkie.