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What is anemia?

Anemia happens when the number of healthy red blood cells in your body is too low. Red blood cells carry oxygen to all of the body’s tissues, so a low red blood cell count indicates that the amount of oxygen in your blood is lower than it should be.

Many of the symptoms of anemia are caused by decreased oxygen delivery to the body’s vital tissues and organs.

Anemia is measured according to the amount of hemoglobin — the protein within red blood cells that carries oxygen from the lungs to the body’s tissues.

Anemia affects more than 1.6 billion people around the world. Women and people with chronic diseases such as cancer have the highest risk of developing anemia.

What causes anemia?

Dietary iron, vitamin B-12, and folate are essential for red blood cells to mature in the body. Normally, 0.8 to 1 percent of the body’s red blood cells are replaced every day, and the average lifespan for red cells is 100 to 120 days. Any process that has a negative effect on this balance between red blood cell production and destruction can cause anemia.

Causes of anemia are generally divided into those that decrease red blood cell production and those that increase red blood cell destruction.
Factors that decrease red blood cell production

The things that typically decrease red blood cell production, causing anemia, include:

  • inadequate stimulation of red blood cell production by the hormone erythropoietin, which is produced by the kidneys
  • inadequate dietary intake of iron, vitamin B-12, or folate
  • hypothyroidism

Factors the increase red blood cell destruction

On the other hand, any disorder that destroys red blood cells at a rate faster than they’re made can cause anemia. This typically occurs due to hemorrhaging, which can happen because of:

  • endometriosis
  • accidents
  • gastrointestinal lesions
  • menstruation
  • childbirth
  • excessive uterine bleeding
  • surgery
  • cirrhosis, which involves scarring of the liver
  • fibrosis (scar tissue) within the bone marrow
  • hemolysis, a rupture of red blood cells that can occur with some medications or Rh incompatibility
  • disorders of the liver and spleen
  • genetic disorders such as:
    • glucose-6-phosphate dehydrogenase (G6PD) deficiency
    • thalassemia
    • sickle cell anemia

Overall, however, iron deficiency is the most common cause of anemia. It accounts for nearly half of all anemia cases, and is a major nutritional disorder worldwide.