Hemoglobin is a protein in red blood cells that carries oxygen. Learn about its structure, function, and what happens when levels are high or low. Hemoglobin is a complex iron-containing protein found in erythrocytes (red blood cells) of most vertebrates that plays a vital role in carrying oxygen and carbon dioxide within the blood. It is also the component that makes our blood red. Hemoglobin is a protein in red blood cells that carries oxygen and carbon dioxide. Learn about hemoglobin test, normal and abnormal levels, causes and symptoms of anemia, sickle cell disease and thalassemia. Hemoglobin is a two-way respiratory transporter, carrying oxygen from the lungs to the tissues and working with the return carry of carbon dioxide. In the blood vessel circulation, hemoglobin has a high affinity for oxygen and a low affinity for carbon dioxide, natural phosphates, and hydrogen and chloride ions. In the venous circulation, these overall affinities are reversed. Hemoglobin is a protein inside red blood cells that transports oxygen from the lungs to tissues and organs in the ...
