Cytoplasm of RBCs contain large amount of hemoglobin which contain iron binds to haem group. it carry and transport oxygen from lungs to all parts of body and return carbondioxide back to the lungs from the different tissues.
Normal level of hemoglobin for men= 13.5 to 17.5 g/dl and for women =12.0 to 15.5 g/dl
Low level of hemoglobin is the indication of anemia
