One of the tests in the mini-physical you get before a blood donation is a check of the hemoglobin level in your blood.
The blood-stick test is to make sure you have enough hemoglobin, the protein that carries oxygen in your red blood cells. Having a low hemoglobin level – known as anemia – can prevent you from donating blood.
In otherwise healthy people, the main reason for anemia is a low level of iron, since the body needs iron to make hemoglobin. You often can restore iron to a normal range in your body by eating more iron-rich foods, including meats, poultry, seafood, dark leafy greens, egg yolks, legumes, oatmeal, peanut butter, raisins, prunes, apricots, soybeans, whole-wheat breads and iron-enriched bread, cereal, pasta, and rice.
If you change your diet and your hemoglobin levels still are too low for donation, you may need to consult your doctor. Anemia is the most common nutritional disorder in the world, and it is especially common in women.