What Is Iron Deficiency?

Defining Iron Deficiency

fatigued woman exercising
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Clinical Definition:

Iron deficiency is a nutritional deficit, which occurs due to inadequate levels of iron in the body. Iron is an essential nutrient for several functions, such as oxygen binding and transport, muscle oxygen use and neurotransmitter synthesis. A deficiency in iron can cause a decrease in immune system functioning ability and compromise growth and development. Iron deficiency has differing levels of severity: It may not be severe enough to cause health impairment, or it can progress to anemia, which can affect various organs in the body.

In Our Own Words:

Iron is a mineral the body needs in order to properly function. Iron deficiency is a lack of iron in the body. It is a very common nutritional deficiency. Inadequate levels of iron interfere with how the muscles store and use oxygen. Iron is also needed to transport oxygen throughout the body.

If the body has depleted or low iron levels, symptoms may not always occur. If iron levels become low enough, a condition known as anemia can develop. Iron deficiency anemia can lead to problems, such as memory difficulties, fatigue and decreased ability to fight infection. 

A Closer Look at Iron Deficiency

About 50 percent of all anemia worldwide is attributable to iron deficiency, with an estimated 841,000 people dying of this condition each year. To put this number in perspective, about this many people live in San Francisco.

The clinical progression of iron deficiency spans 3 stages.

Stage 1: Negative Iron Balance. Negative iron balance results from the body needing more iron than it procures from the diet. This condition commonly affects pregnant women, people who have lost a lot of blood and people who are undernourished. People who have negative iron balance end up depleting iron stores in the bone marrow.


Stage 2: Iron-Deficient Erythropoiesis. During the second phase of iron deficiency, called iron-deficiency erythropoiesis, a prolonged negative iron balance eventually takes its toll on your body. During this stage, the production of red blood cells is affected, and on examination (blood smear), these red blood cells appear small, or microcytic. Furthermore, hemoglobin synthesis is impaired. Please remember that red blood cells--by means of hemoglobin--are responsible for carrying oxygen throughout the body.   

Stage 3: Iron-Deficiency Anemia. After some time, a person who is iron deficient eventually exhibits anemia where the actual levels of hemoglobin and hematocrit fall by about 10 to 15 percent. Furthermore, red blood cell morphology further changes, and the red blood cells take on weird shapes (think target cells and cells shaped like pencils or cigars).

Depending on severity, here are some symptoms of iron-deficiency anemia:

  • pallor
  • fatigue
  • decreased ability to exercise
  • fissures in the corners of the mouth (cheilosis)
  • spooning of the fingernails (koilonychia)

With iron deficiency anemia, the cause of the anemia (for example, surgery to stop bleeding) must be treated as well as supplementing iron consumption. Mild anemia may be treated with dietary changes or medicine; whereas, severe anemia is treated with intravenous iron supplementation, iron injection or blood transfusion.


Johns Hopkins Medicine. “Iron-Deficiency Anemia.” Accessed September 2013.

Centers for Disease Control and Prevention. “Iron and Iron Deficiency.” Accessed September 2013.

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