Iron deficiency occurs when a person has low levels of stored iron. The initial signs of iron deficiency are often subtle. Patients may have a reduced ability to perform physical tasks and lower mental productivity. In many cases, others may attribute the patient’s reduced activity to laziness or other behavioral or motivational problems.

Meanwhile, a person with severe depletion of iron stores may develop iron-deficiency anemia. This occurs when low levels of stored iron are accompanied by pale and small red blood cells that cannot carry enough oxygen from the lungs to the tissues. Iron-deficiency anemia occurs when a person does not consume enough dietary iron to replace the iron used to produce hemoglobin (the component of red blood cells that brings oxygen to tissues and muscles).

Many conditions can cause anemia. Causes of iron-deficiency anemia include:

• Inadequate levels of iron in the diet. This is especially true of infants and children. Diets that are low in fat or high in sugar are often low in iron. Diets high in fiber may slow the absorption of iron. However, it is relatively rare for a person in the United States to develop iron-deficiency anemia as a result of inadequate levels of iron in the diet. This is especially true since the advent of iron-fortified infant formulas and cereals.
  
  
• Poor absorption of iron in the digestive tract. This may occur as a result of intestinal disease (e.g., Crohn’s disease, celiac disease) or a side effect of surgery. Some prescription medications also may prevent proper absorption of iron. Low levels of folate, vitamin B12 and vitamin C also are associated with poor absorption of iron.
  
  
• Chronic bleeding. This can be the result of many different factors, including heavy menstrual bleeding. Other factors that can cause such bleeding include ulcers, tumors, uterine fibroids, colon polyps, colorectal cancer, gastrointestinal bleeding, hookworm infection, regular use of aspirin and nonsteroidal anti-inflammatory medications, urinary tract bleeding, and hemorrhoids.

Patients with iron-deficiency anemia may experience fatigue, weakness, headaches and higher sensitivity to cold temperatures. Their skin may be noticeably pale, as hemoglobin levels fall, leaving less bright red pigment in the blood. Dark-skinned people may notice paleness of the tongue and eye lining. Some patients experience heart palpitations, shortness of breath during physical activity, restless legs and hair loss.

Other symptoms of iron-deficiency anemia may include decreased work and school performance, slow cognitive and social development during childhood, difficulty maintaining body temperature, decreased immune-system function, and/or glossitis (an inflamed tongue). Recent studies have even found evidence that low levels of iron may be responsible for many forms of baldness.

Heart problems are often associated with iron-deficiency anemia. Anemia prevents adequate levels of oxygen from circulating in the body. As a result, the heart experiences an increased demand to move oxygen, which stresses the heart and causes symptoms such as heart palpitations, shortness of breath during physical activity and chest pain. Patients may develop an enlarged heart and may even experience heart failure.

In many cases, an iron deficiency can progress to the latter stages without being diagnosed. Hemoglobin or hematocrit blood tests can reveals low levels of these substances.

People are most vulnerable to iron-deficiency anemia during rapid growth cycles, such as during infancy, adolescence and pregnancy. Iron-deficiency anemia is most likely to develop in children between the ages of 6 months and 3 years. It can substantially impair mental and psychomotor development in children of this age group. Young children with iron-deficiency anemia may develop a heart murmur and have an increased vulnerability to lead poisoning and infections. Breastfed infants who are not started on solid food after 6 months of age and babies given cow’s milk prior to 12 months of age are especially vulnerable.

Research has also found that children and teens with iron deficiencies may score lower on cognitive testing of thinking, learning and memory. Children in many poorer parts of the world are vulnerable to having low levels of iron.

Women also are at higher risk for iron-deficiency anemia than men. Women are especially vulnerable during pregnancy. Pregnant women who experience iron-deficiency anemia during pregnancy are at greater risk of delivering prematurely. Their babies also are more likely to be born with a birth weight that is lower than average. Heavy menstrual bleeding also can trigger iron-deficiency anemia.

People with kidney failure, especially those who are on dialysis, have a high risk for developing iron deficiency anemia because their kidneys cannot create enough erythropoietin, a hormone needed to make red blood cells.

Alcoholism also is associated with this disorder. Diets that contain insufficient iron can contribute to iron-deficiency anemia, but this is rare in the United States. Iron deficiency is sometimes associated with pica, a disorder in which patients crave nonfood substances such as ice, clay or paste. Women and children are especially susceptible to pica.

Patients also can develop a condition in which the body contains too much iron. In most cases, people who consume too much iron are at no increased health risk because the body typically adjusts its absorption level based on the amount of iron stores that are present. However, some people have bodies that are less efficient at this task, which puts them at risk for iron toxicity.

In particular, people with hemochromatosis may experience increased absorption of iron. Also known as iron overload, hemochromatosis is a disorder that interferes with iron metabolism. It occurs when too much iron builds up in the liver and heart, leading to cirrhosis of the liver and heart failure. Hemochromatosis is a common genetic disorder in the United States and affects 1.5 million Americans. Repeated blood transfusions and massive doses of iron supplements also can cause hemochromatosis.

Initial signs of hemochromatosis are similar to those of iron deficiency and include fatigue and lethargy. Other symptoms may include joint pain, weight loss, generalized darkening of the skin, loss of body hair, and/or weakness. However, hemochromatosis is often not diagnosed until excess iron stores have already damaged an organ. Excess iron can damage tissues, especially tissues in organs that store iron, such as the liver. Hemochromatosis also increases the risk of getting arthritis, liver cancer, diabetes, heart disease and infectious diseases (bacteria thrive on blood that is rich in iron). People who abuse alcohol are particularly at risk for these symptoms because alcohol can damage the intestines and impair its ability to prevent the absorption of excess iron.

Men are more likely than women to be diagnosed with hemochromatosis, as women tend to lose iron through menstruation.

High levels of iron may also pose other risks. A recent study involving mice found that baby mice who consumed iron-fortified formula were at higher risk for developing brain degeneration of a type associated with Parkinson’s disease. A similar link between human babies who consume iron-fortified formula and adult Parkinson’s has not been established, but researchers are looking into the matter. Patients with Parkinson’s disease typically have higher levels of iron in their brains.

Following are the recommended dietary allowances of iron in milligrams, based on age: