What is Microcytic Anemia?

What is Microcytic Anemia?
What is Microcytic Anemia? (Image: Photo CC Ed Uthman, http://flickr.com/photos/euthman/2274260085/)

Microcytic anemia refers to the presence of red blood cells (RBCs) smaller than normal in a lab sample. This finding is usually coupled with reduced hemoglobin in the RBCs, known as "hypochromic anemia" because the cells are paler than normal. Microcytic anemia is defined as a Mean Cell Volume (MCV) of less than 80 cubic mm. Each lab sets its own range, so this number may vary.


The most common cause of microcytic anemia is iron deficiency. Iron is necessary to the formation of hemoglobin so, when it is lacking, RBCs are small (microcytic) and pale (hypochromic). The body stores iron in the bone marrow. When iron intake is not enough to provide for daily needs, the storage iron (ferritin) is activated. If iron stores continue to be depleted without replacement, the body's ability to make new RBCs (erythropoiesis) will be impaired.

Anemia of Chronic Blood Loss

In adults, microcytic anemia is often the 1st sign of chronic internal bleeding, usually in the gastrointestinal tract. Further testing should be done to determine the site of the bleed. In premenstrual women, microcytic anemia may be caused by menstruation; however, other causes of internal bleeding should always be ruled out. Ulcers are 1 common cause of chronic internal blood loss.

Iron in Food

Iron is difficult to absorb from food, and only about 1/10 of the amount consumed daily is used. If iron stores are depleted, the percentage of iron absorbed increases. The body needs to replace only about 1 mg of iron a day. The amount of iron needed increases during times of growth and healing, so children, teenagers and pregnant and nursing women are more prone to deficiency. Iron is present in meat and in several grains and beans, including chickpeas, lentils and navy beans.

Anemia of Chronic Disease

Microcytic anemia can be a side effect of an infection, an inflammatory disease or cancer. Three factors are thought to create this anemia: 1) RBCs with a shortened lifespan; 2) diminished erythropoiesis (fewer new RBCs are made); and 3) inefficient recycling of iron from dying RBCs, so iron loss is increased. The anemia of chronic disease usually begins as a normocytic anemia (RBCs of normal size, but fewer cells present) which progresses to microcytic anemia over time.

Signs and Symptoms of Anemia

Microcytic RBCs on a routine lab test may be the 1st sign that anemia is present. Other signs and symptoms include: pale skin, especially the conjunctiva of the eye, the lines of the palm and the gums; shortness of breath during exercise; dizziness; fatigue; and decreased stamina. Anemic women may experience heavy menstrual flows. Some people may have the urge to eat dirt or chalk, a symptom known as pica. In anemia of chronic disease, the main symptoms are those of the underlying disease.


Iron-deficiency anemia can be prevented by the combination of a balanced diet and a healthy digestive tract. If anemia is diagnosed, any internal bleed must be identified and treated. In anemia of chronic disease, the anemia resolves with the disease, and drugs that encourage the production of RBCs may be used. Iron supplementation is often used to resolve microcytic anemia, but diagnosis of the cause should come first.


Iron supplementation is not necessary for everyone. Excessive intake of iron is dangerous. Consult a health practitioner for more information about anemia.

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