My vision goes black when I stand up suddenly??

It has something to do with your blood pressure being a little bit low. When you stand up from sitting or lying down, the blood is pooled in the lower part of your body, and it takes a few seconds for your heart to pump more blood to your brain. Be careful standing up - be prepared to grab onto something sturdy if you get dizzy. Make sure you don't go too long without eating so your blood sugar doesn't get too low, because that can cause dizziness. Also talk to your doctor about this. It's possible you may have a condition that needs treatment.

I used to have this problem when I was your age, but it improved a lot by the time I was in my 30s or 40s. Just be careful when you stand up.

I would go to your GP to get your blood pressure and bloods tested.

I have had this all of my life and went to the GP several times but they didn't seem concerned. However I now have a b12 deficiency and they are looking at it as a symptom of something more serious so it really does pay to go!

this can also point to heart conditions and other things so it really is best to get checked out.

However saying all of that.

Do you eat regular meals? Do you eat the right protein/carb/sugar ratios each day?

your blood sugar levels going up and down will make you feel this way, try to eat every 2-3 hours, not a full meal but say half to a 1/4 of a normal sized meal.

i have this too you stand up too fast everything goes black for a second and you feel light headed its due to the lack of blood in the brain when you stand up all the blood in your brain is building and when you get up too fast the blood rushes down to your body which causes this. a study has been shown that this behavior may make people with this condition more likely to have heart problems

sometimes i get that too when i stand up, i doubt its iron deficiency. I'm pretty sure its the blood rushing to your head, from your head, and to other places in your body.