The human body contains enough iron to make a metal nail 3 inches (7.5 cm) long.

Iron is a mineral that helps your body function. Most of it is found in hemoglobin, which is a protein in your red blood cells. Each hemoglobin molecule has four iron atoms that grab onto oxygen as blood moves through your lungs.About 70% of your body's iron is used for this oxygen transport. Another 25% is stored in a protein called ferritin. This protein stays in your liver, spleen, and bone marrow to be used later if you do not eat enough iron.A small amount of iron is also found in myoglobin. This is a protein that stores oxygen in your muscles so you have energy to move. The rest of the iron helps your body's enzymes work correctly.Your body is very good at recycling this metal. It makes about 200 billion new red blood cells every day. This process needs 20 to 25 milligrams of iron daily. Most of that iron comes from old blood cells that the body breaks down and reuses.