About a week ago, and maybe it's all in my head, but i find it much harder to keep an erection since then. I didn't donate blood normally. They needed more red blood cells, so they removed a pint of blood, split the plasma and the cells, and put the plasma back in my blood stream, then took out another pint, and did the same thing. So basically I lost 2 times the amount of blood cells, while losing little plasma. Has anyone else done this and then have trouble with erections. Even when i work out i get tired much quickly.