Anemia is a lower than normal number of red blood cells (erythrocytes) in the blood, usually measured by a decrease in the amount of hemoglobin. Hemoglobin is the red pigment in red blood cells that transports oxygen.

There are many types and potential causes of anemia. For information about a specific type of anemia, see one of the following articles:

• Anemia - B12 deficiency
• Anemia - folate deficiency
• Anemia - iron deficiency
• Anemia due to chronic disease
• Hemolytic anemia
• Hemolytic anemia - G-6-PD deficiency
• Idiopathic aplastic anemia
• Idiopathic autoimmune hemolytic anemia
• Immune hemolytic anemia
• Immune hemolytic anemia - drug-induced
• Megaloblastic anemia
• Pernicious anemia
• Secondary aplastic anemia
• Sickle cell anemia

The cause varies with the type of anemia. Potential causes include blood loss, nutritional deficits, many diseases, medication reactions, and various problems with the bone marrow. Iron deficiency anemia is most common in women who have heavy menstrual periods.

Risk factors include heavy periods, pregnancy, older age, and diseases that cause anemia.

Possible symptoms include:

• Fatigue
• Chest pain - angina
• Shortness of breath

The doctor will perform a physical examination, and will look for the presence of a pale complexion and rapid heart rate.

Anemia can be confirmed by a red blood count or hemoglobin level. Other tests depend on the type of anemia.

Treatment should be directed at the cause of the anemia. In some cases, blood transfusions and the medication erythropoeitin will correct anemia.

The outlook depends on the cause.

Severe anemia can cause low oxygen levels in vital organs such as the heart and can lead to heart attack.

Call your health provider if you have any of the symptoms of anemia or any unusual bleeding.