What does it mean if you stand up sometimes and can't see?!

What does it mean if you stand up sometimes and can't see?

Sometimes when I stand up I can't see. Like it's all black and then things slowly fade in a few seconds later. Is this bad? What does it mean?

1 week ago
I am age 14. It doesn't happen often but I have a friend who doesn't eat much, and it happens to him. He was told by his doctors to eat because he is underweight. I've also developed his eating habbits and now I eat even less than him, so I'm worried about what might happen to me.

I've had these "blackouts" happy every once in a while even when I ate good, but now I'm worried because I just got one eariler today when I'm not eating good.

that is called postural hypotension. When you stand up, because your blood pressure is low, all the blood drains from your brain and you experience the loss of vision, can also experience fainting, you don't mention your age, or if you are taking medication, these would be helpful to know in order to suggest a course of action for you.