Oxygen saturation (medicine)
Oxygen saturation is the fraction of oxygen-saturated hemoglobin relative to total hemoglobin (unsaturated + saturated) in the blood. The human body requires and regulates a very precise and specific balance of oxygen in the blood. Normal blood oxygen levels in humans are considered 95–100 percent. If the level is below 90 percent, it is considered low resulting in hypoxemia. Blood oxygen levels below 80 percent may compromise organ function, such as the brain and heart, and should be promptly addressed. Continued low oxygen levels may lead to respiratory or cardiac arrest. Oxygen therapy may be used to assist in raising blood oxygen levels. Oxygenation occurs when oxygen molecules () enter the tissues of the body. For example, blood is oxygenated in the lungs, where oxygen molecules travel from the air and into the blood. Oxygenation is commonly used to refer to medical oxygen saturation.
Iron
Iron plays an important role in biology, forming complexes with molecular oxygen in hemoglobin and myoglobin; these two compounds are common oxygen-handling proteins in vertebrates (hemoglobin for oxygen transport, and myoglobin for oxygen storage). Iron is also the metal at the active site of many important redox enzymes dealing with cellular respiration and oxidation and reduction in plants and animals. Iron is distributed throughout the human body, and is especially abundant in hemoglobin. Total iron content of the adult human body is approximately 3.8 grams in males and 2.3 grams in females. Iron is a critical element in the metabolism of hundreds of proteins and enzymes involved in diverse body functions, such as oxygen transport, DNA synthesis, and cell growth.