Blood loss from heavy menstrual periods or internal bleeding
When you're anemic, your body either produces too few healthy red blood cells, or destroys them faster than they can be replaced or loses too many of them. If your diet lacks certain vitamins and minerals, the production of hemoglobin can slow down.
Types of anemia caused by decreases in red cell production include iron deficiency anemia and vitamin deficient anemia.
If something in the body destroys or attacks red blood cells, the bone marrow tries to produce more blood. If the destruction of red blood cells is rapid, the marrow can't catch up. This problem is often inherited. The resulting anemia is called hemolytic anemia.
A severe bleeding episode can result in temporary anemia until the body has had time to make up the blood that was lost. But even small, persistent losses of blood may cause anemia if you have a poor diet. A healthy person whose diet contains plenty of iron and vitamins can produce large amounts of new blood, reducing the risk of anemia.