I went out to the stairwell by my office to take a phone call. I was squatted down for the call (probably ~5 minutes). When I stood up, I must've stood up too fast and got dizzy/light headed. I leaned on a large office printer that wasn't in use and my vision went dark. Next thing I knew, I had fallen over to my left and hit my head on a folded up table.

It couldn't have been longer than one or two seconds. I feel MOSTLY fine. This happened about an hour ago and I've just got a slight headache.