I had problems with hemoglobine for years, but since I take some supplements for months I am fine now, that's why they let me donate... But if I do not take them my hemoglobine level is low, because we (women in our family) have problem with processing iron from the food.
So it's not that I would have anemia, but maybe thanks to the fact that my hemoglobine is fine just cause of supplements, it might influence me stronger when I do lose some blood? I have no idea.
Anyway, I feel better now. After few hours of sleep and some food.