Dizziness is usually a sign that your blood pressure is low, and dropping a little more when u Stand or move to fast..(postural drop)
It always happens to me when I am healthy (dieting!) I think because of the reduction of sodium in my diet, so there r a few thing that may help.
Add a little more salt to your meals,
Defo increase your fluid intake, (low Bp can indicate low blood volume) if it isn't at the max already, and take Into account that increasing fluid with reduced sodium levels further, (Our bodies may be used to high salt snacking, processed food and occassional takeaways)
Also just practice solutions, stand slowly and don't run.. Hope some of that helps.x
Louise.