I remember one time I got up too fast while sick. I greyed out, falling to the floor slowly while perfectly conscious but without vision and little control over my body. I was alright, but it was definitely a unique experience
That happens to me all the time and I am so tired of it. I don't even get up that fast and I still go blind for a few moments. I hope it's not a heart problem.
I just got up from a seizure. I tried getting up from my couch and got a head rush like always, then everything went blank and I remember the feeling of my head slamming on the floor a bunch of times, then I woke up seeing my dad looking at me, then he just said "I think you just had a seizure". It definitely scared the hell out of my and I'm still shaking a little bit. I stayed down for a while and yelled for someone to place a pillow under my head, and i stayed there for a while just waiting for it to happen again. Thankfully it didn't, and i feel fine now.