Fatigue is a very common complaint, reported to general practice doctors up to 25 percent of office visits. The incidence of fatigue is even higher than this, however, since many people experiencing fatigue do not report it to their doctors. Many people are tired because of busy lives, work and home obligations, and not getting enough rest. Fatigue is also a component of many illnesses and chronic diseases. Often fatigue is dismissed by doctors either as being a normal part of life, or as being a result of emotional disturbances or stress. Women are three times more likely to have fatigue than men.
Iron Deficiency Anemia
One common cause of fatigue in reproductive age, menstruating women is iron deficiency anemia. A lesser known cause but possibly equally prevalent is low ferritin, caused by low iron stores. Iron deficiency anemia occurs when there is not enough iron in the body, and the production of red blood cells is affected. It can affect up to 20 percent of women. Causes of iron deficiency anemia in menstruating women include heavy periods, gynecological diseases such as fibroids or adenomyosis, gastrointestinal bleeding, and gastrointestinal malabsorption.
Iron deficiency anemia is often assessed by taking blood and measuring the hemoglobin level: hemoglobin is a protein in red blood cells that binds to iron, and transports oxygen in the blood. Hemoglobin is measured as part of a complete blood count (CBC). Normal hemoglobin range in the blood is usually 12 to 15 g/dL, but the normal range can vary slightly depending on the lab. In iron deficiency anemia hemoglobin values are lower than 12 g/dL.
- Shortness of breath
- Cold hands and feet
- Pale skin
- Chest pain
- Restless legs syndrome
Iron deficiency anemia is usually easily recognized and treated. The CBC is a very commonly performed blood test, and low hemoglobin, plus other results contained within the CBC panel, is a good indicator of iron deficiency anemia. It is treated with oral iron, which can be obtained in drug stores without a prescription. Side effects of oral iron include nausea, vomiting, constipation, diarrhea, dark colored stools, and abdominal pain. Iron supplements should not be taken without having a doctor monitor the blood levels of iron, since too much iron can cause buildup of excess iron and organ damage.
Low Ferritin and Fatigue
Although the importance of treating iron deficiency anemia is well recognized, many health practitioners do not test the body’s iron stores, and low iron stores, indicated by low ferritin levels, can also cause fatigue. Ferritin is a protein that stores iron in the body. It is not measured by the CBC, but can be measured by a separate blood test. Usually the only consequence of low ferritin is thought to be that it might put a person at risk for developing iron deficiency anemia. However, low ferritin on its own, even without anemia, can cause fatigue.
Several studies have shown that in people with fatigue, with normal hemoglobin levels, oral iron supplementation can improve fatigue. This was particularly true when ferritin levels were below 50 µg/L. Intravenous iron supplementation is another option for treatment and may be particularly appropriate if the ferritin levels are below 15 µg/L. Most labs use 12 -150 µg/L as the normal range for women for ferritin, although this may vary from lab to lab. Therefore, many women who could benefit from iron supplementation for fatigue may be classified as having “normal” ferritin levels.
The normal reference ranges are obtained by sampling ferritin concentrations in populations of women, many of whom may have had iron deficiency, and whether the lower limit of the normal range is actually too low has been brought into question. The fact that iron supplementation improves fatigue when ferritin levels are below 50 µg/L would suggest that this is the case. Therefore, all women should be aware that low iron levels can contribute to fatigue even if anemia is not present, that checking ferritin is an important part of an investigation into unexplained fatigue, and that even if their ferritin levels are deemed to be “normal”, that if the levels are below 50 µg/L, iron supplementation may improve their fatigue.
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This post was first published on April 2, 2014.