What do red blood cells do?
Red blood cells carry oxygen from the lungs to every part of the body and help carry carbon dioxide back to the lungs. They get their red color from a protein called hemoglobin.
Each red blood cell is packed with about 270 million molecules of hemoglobin, an iron-containing protein that grabs oxygen in the lungs and releases it in tissues that need it. Red blood cells are shaped like flattened discs with a dip in the middle, which gives them more surface area and lets them bend through tiny capillaries.
Red blood cells are made in the bone marrow, at a rate of about two to three million every second. Mature red blood cells have no nucleus, which leaves more room for hemoglobin. They live for about 120 days before being broken down, mainly in the spleen and liver.
When there are too few
Having too few red blood cells or too little hemoglobin is called anemia. It can make people feel tired, weak and short of breath. A common cause is a lack of iron, which the body needs to make hemoglobin. Blood tests can check red blood cell levels.
Did You Know?
Red blood cells make up roughly a quarter of all the cells in the human body, around 25 trillion in an adult.
This answer is general information, not medical advice. For a personal health question, talk to a doctor.