Hemoglobin is the biochemical in your red blood cells which transports oxygen from your lungs to your cells. It is based upon an iron atom, which binds to the oxygen to carry the oxygen molecule. You may need more iron (such as a suppliment) or eating more red meat might be enough. If you are vegetarian, iron pills may be best for you. What did your doctor recommend? You might be feeling weakness or less energy as a result of the iron deficiency.