Anemia (AmE) or anæmia/anaemia (BrE), from the Greek (Ἀναιμία) (an-haîma) meaning "without bloo," is defined as a qualitative or quantitative deficiency of hemoglobin, a molecule inside red blood cells (RBCs). As hemoglobin carries oxygen from the lungs to the tissues, anemia leads to hypoxia (lack of oxygen) in organs. Since all human cells depend on oxygen for survival, varying degrees of anemia can have a wide range of clinical consequences.