HEMOGLOBIN IS A BLOOD TEST THAT MEASURES THE LEVEL OF FREE (Hgb) IN THE LIQUID PART OF THE BLOOD. Hgb IS A PROTEIN INSIDE THE RED BLOOD CELLS THAT CARRIES OXYGEN THROUGHOUT THE BODY. HEMOGLOBIN BLOOD TEST REVEALS HOW MUCH Hgb IS IN A PERSON’S BLOOD THIS TEST IS ALSO USED TO HELP DIAGNOSE AND MONITOR ANEMIA AND POLYCYTHEMIA VERA.