Anemia is a condition where there is a lower than normal number of red blood cells in the blood, usually measured by a decrease in the amount of hemoglobin. Hemoglobin is the oxygen-carrying part of red blood cells. It gives these blood cells their red color.

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

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

The cause varies with the type of anemia. Potential causes include blood loss, poor diet, many diseases, medication reactions, and various problems with the bone marrow, where blood cells are made. 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
• 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 erythropoietin 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 a heart attack.

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