Dr. Greene’s Answer:
A hemoglobin test measures hemoglobin levels — not iron. The most common reason for low hemoglobin is low iron, but it can be caused by many things. The CBC (complete blood count) gives more information, but still does not measure iron. Lead toxicity and thalassemia, can cause it–even hemoglobin F (fetal hemoglobin). Low iron should be corrected after three months of taking iron.
Thalassemia is a hereditary condition of hemoglobin that is different from average hemoglobin. The most common form causes no problem–except people get treated with iron who don’t need it. A level of 5.1 is lower than it usually gets from simply an iron deficiency in a 12-month-old with a normal diet and no bleeding. I recommend consulting with a pediatric hematologist (blood specialist) to pinpoint what is going on. It will most likely be fine, but well worth knowing either way.
Low hemoglobin from thalassemia trait is fine, but some other causes–like low iron–can affect development if not corrected. If the problem is iron, you need to find out why it has not gone up. Kids with thalassemia trait can get iron deficient too, just like any other kids, but you shouldn’t need more than three months of iron to correct the problem.