Why does my vision go black whenever I stand up?!

It's called orthrostatic hypertension. It is when your blood pressure sudenly drops. It's not that bad, it happens to everyone. :) If you really dont like it, you can fix it in a few ways..
Standing up more slowly can give the blood vessels more time to constrict properly
Breathing deeply and flexing the abdominal muscles while rising helps maintain blood and oxygen flow to the brain
Avoiding bodily positions that impede blood flow
Hope I helped.

http://en.wikipedia.org/wiki/Orthostatic…

That is a circulatory or hydration issue, not a vision issue (because you get dizzy on top of the darkening vision).
If you are dehydrated you will get dizzy (you're dehydrated long before you feel thirsty, so keep up the fluid intake).
If you are anemic you can get dizzy from standing up too quickly. If you have low blood pressure you sill get dizzy if you stand up too quickly (or even if you sit up from a prone position).
If you have any inner ear issues (history of ear infections, current ear infection, ear trauma) that can cause the dizziness as well.

Low blood pressure is one possibility. try exercising a bit before you stand up, to get your body in gear before you get vertical.

im not a doctor by any means but sounds like a circulation problem involving low blood pressure id go to the doctor and find out though. they will probably tell you to drink more water and eat more foods with iron in them

Happens to me 2
It cuz ur hungry so like u dont have much energy in your body or ur focused on like tv or ur phone

Doctor