Microcytosis is a term used to describe red blood cells that are smaller than normal. Anemia is when you have low numbers of properly functioning red blood cells in your body. In microcytic anemias, your body has fewer red blood cells than normal. The red blood cells it does have are also too small. Several different types of anemias can be described as microcytic.
Microcytic anemias are caused by conditions that prevent your body from producing enough hemoglobin. Hemoglobin is a component of your blood. It helps transport oxygen to your tissues and gives your red blood cells their red color.
Iron deficiency causes most microcytic anemias. Your body needs iron to produce hemoglobin. But other conditions can cause microcytic anemias, too. To treat a microcytic anemia, your doctor will first diagnose the underlying cause.