Nothing.
Haemoglobin is produced from red blood cells. If your body is like mine and only chucks out a measly number of red blood cells, you're not going to get a lot of haemoglobin out of it. Increasing your iron intake will help get more juice out of a low blood cell count, but won't create more blood cells.
Best source of iron is in red meat, so bin that faddy vegan / vegetarian diet.