This is a complex blood protein. It is contained in red blood cells – erythrocytes. Hemoglobin contains an iron ion surrounded by a protein globina. This formation in the body performs many important functions: - binds oxygen and carries it from the lungs to all tissues and organs; - carries carbon dioxide to the lungs; - normalizes the acid-alkaline balance of the blood. Oxygen is an essential element necessary for the existence of every cell. And without the aid of hemoglobin he can't get to them easy. Even the slightest decrease in its level affects the functioning of the body. Therefore, it is important to know what is the hemoglobin that is necessary for its formation and how to maintain an adequate level in the blood.