How bad is the 3 hour glucose tolerance test during pregnancy-for gestational diabetes?

I had to get it done, it just hurt that they kept pricking me in the same spot because i only had one vein good enough to get blood from, and i felt horribly sick because i couldn't eat or drink anything except that drink, and this time i had to drink the whole thing and i couldn't drink water in between gulps of the gross drink. so i just fell asleep in between each hour, oh and a warning, dont rush out and eat alot immediately. I did and threw up everything right after i ate it.