A normal hemoglobin level does not necessarily indicate that you are not anemic, meaning your blood is not low in iron. Yet, the hemoglobin level obtained in your doctor’s office does not reflect total body stores of iron. It’s possible to have a normal hemoglobin, that is, a normal amount of iron in the blood, yet have vital tissues throughout your body deficient in iron. Some people have symptoms of iron-deficiency anemia, even with a normal hemoglobin. To really be sure you have enough iron in your body, your doctor may send you to the laboratory to measure the serum ferritin, the level of iron in blood that accurately reflects iron stores. (Normal values are 7 to 140 micrograms per liter (mcg/l) in children, 20 to 120 micrograms in women, 20 to 300 micrograms in men.) If your serum ferritin level is normal, you can rest assured that you have adequate iron stores throughout your body.
Serum ferritin levels detect iron deficiency in the early stages; a low hemoglobin reflects a much later stage of iron deficiency. This is an important consideration, since with a normal hemoglobin and low ferritin levels the iron stores can be restocked by simply increasing the amount of iron in your diet. By the time the hemoglobin is low, iron supplements are usually needed. Symptoms of iron deficiency anemia, such as being tired, irritable, and having difficulty concentrating, may be present long before anemia is reflected by the hemoglobin tests. That is why a serum ferritin is an earlier and more sensitive indicator of iron deficiency.