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Other name(s):

carbonyl iron, desiccated ferrous sulfate, ferrous fumarate, ferrous gluconate, ferrous sulfate

General description

Iron is an essential element important in the development of red blood cells, which carry oxygen to all parts of the body. However, iron is extremely poisonous in large doses. Iron overdose is the number one cause of pediatric poisoning deaths in the United States.

Iron functions primarily as the oxygen-carrying component of hemoglobin, the red pigment inside red blood cells that gives blood its characteristic color. Iron is also necessary for the formation of myoglobin, which is found in muscle tissue. Myoglobin supplies oxygen to muscle cells and plays a role in muscle contraction.

Iron helps to maintain the health of red blood cells and muscle tissue, and it contributes to collagen synthesis and the function of the immune system.

Medically valid uses

Iron is primarily used to treat iron-deficiency anemia.

Pica, an unusual appetite for non-food items such as ice, mud, clay, laundry starch, paint chips, or ashes, can sometimes be treated with iron supplements. Pica often occurs because of an unrecognized iron deficiency.

Depressed immune function, when caused by iron deficiency, can be improved with iron supplements.

Unsubstantiated claims

Please note that this section reports on claims that have NOT yet been substantiated through scientific studies.

Iron has been said to stimulate the immune system, aid in the treatment of alcoholism, and improve athletic performance.

Recommended intake

Many conditions increase the need for iron. Those who have recently lost a lot of blood or have donated blood, as well as those with an excessively heavy menstrual flow or undergoing hemodialysis may need an iron supplement.

Medical conditions and procedures that cause an increased need for iron include burns, achlorhydria (decreased acid production), and a gastrectomy (surgical removal of the stomach). Conditions causing long-term blood loss (such as hemorrhoids, peptic ulcer, or hookworms) may also result in increased iron needs. Aspirin and other arthritis medications may cause microscopic intestinal bleeding that, over time, results in iron deficiency. Athletes may have greater iron requirements due to increased losses of iron in sweat and increased hemoglobin production.

Women who are pregnant or breastfeeding may need to take mineral supplements, but must consult a physician before doing so. Low iron levels during pregnancy increase the possibility of premature and low birth weight babies.

As indicated below, iron is measured in milligrams. The RDA is the Recommended Dietary Allowance.



Infants (0 to 6 months)

6 mg

Infants (6 months to 1 year)

4–10 mg

Children (1 to 10 years)

10 mg

Boys (11 to 18 years)

12 mg

Men (19+ years)

10 mg

Women (11 to 50 years)

15 mg

Women (50+ years)

10 mg

Pregnant women

30 mg

Breastfeeding women

15 mg

Iron supplements come in different forms. These forms have been developed in an attempt to decrease the gastrointestinal problems, such as constipation, associated with iron. Each form has a different percentage of magnesium. Ferrous fumarate and ferrous sulfate contain the highest concentrations of iron, with ferrous gluconate containing the lowest.

Dosage is expressed either as the amount of iron present or the percentage of iron in the preparation. Be sure to read the label carefully to see if it expresses the amount of elemental iron or the total weight of the compound. For example, 325 g of ferrous sulfate contains only 65 mg of elemental iron.

Carbonyl iron is a form of elemental iron that has been very finely ground to improve its absorption and is one of the safer forms of iron.

Photo of a raw steak

The most absorbable form of iron is heme iron, which is found in red meat and poultry. Absorption is enhanced by consumption of vitamin C in conjunction with iron-rich foods.

In order for the gastrointestinal system to absorb iron, the stomach needs to be acidic. Certain antacids, such as calcium bicarbonate, can change the pH level of the stomach to a very alkaline environment. Therefore, excessive use of antacids may interfere with iron uptake.


Nutrient Content per 100 grams

Brewer's yeast

17.3 mg


11.8 mg

Wheat germ

9.4 mg


8.6 mg

Pistachio nuts

7.3 mg

Egg yolks

7.2 mg

Beef liver

6.5 mg


6.2 mg

Kidney beans

6.1 mg


5.5 mg

Baker's yeast

4.9 mg


3.2 mg

Pork and ham (varies with cut, does not include organs)

2.5 mg

White enriched bread

0.5 mg


1.8 mg

The major problem associated with too little iron in the body is anemia, particularly microcytic hypochromic anemia. This conditions results in red blood cells that are smaller than usual and do not contain a normal amount of hemoglobin. This type of anemia may result in weakness, paleness of skin (pallor), fatigue, shortness of breath, and headache.

Pica may occur with mild iron deficiencies. Pica is a condition characterized by an abnormal appetite for non-food items. For instance, the pica commonly associated with iron deficiency is a hunger for ice and, in some areas of the country, clay. (Note: pica in young children is not normally associated with iron deficiency.)

Side effects, toxicity, and interactions

Iron is extremely toxic in large amounts. In as few as three to four days, toxic levels of iron can result in death. In severe overdose, iron rapidly destroys the lining of the intestinal tract and may lead to multiple perforations of the intestine. Free iron ions in the bloodstream destroy the endothelium (the lining of the blood vessels) and produce irreversible shock. An excess of iron can also cause severe liver damage.

Iron supplements, including prenatal and children's vitamins, are usually packaged in brightly colored tablets. Young children find these very attractive and may attempt to eat an entire bottle. Because iron is extremely toxic and large overdoses are usually fatal, it is imperative to keep all iron-containing medications away from children. Almost 100 percent of iron poisonings occur in children. Iron is the leading cause of fatal poisoning in children.

A normal side effect of taking iron is constipation or a black stool. Taking a stool softener may offset this problem.

Taking daily doses of iron above the recommended allowance may cause an accumulation of iron, leading to iron overload. This damages the liver (causing cirrhosis), heart, pancreas, pituitary gland, and other organs. This condition is called acquired hemochromatosis.

Studies are being done to determine whether excessive iron supplementation may play a role in certain cancers. Finally, excess iron intake has been associated with increased risk for cardiovascular disease.

Various types of blood diseases, some of which are serious, can result in anemia. Taking iron supplements can mask these conditions and allow them to go undiagnosed. Some blood diseases, if treated with iron, may result in iron overload. They include sickle cell anemia, G6PD (glucose-6-phosphate dehydrogenase deficiency), hereditary spherocytosis, hereditary elliptocytosis (1 in 2000), pyruvate kinase deficiency, acquired or genetic hemochromatosis, and thalassemia.

Iron preparations often contain tartrazine or sulfites. People who are allergic to aspirin have a higher sensitivity to tartrazine. People who have asthma are more likely to be allergic to sulfites. Therefore, people who are allergic to these chemicals or are asthmatic should use caution in selecting an iron preparation.

Antacids and cimetidine (a drug that blocks the production of stomach acid) can decrease the amount of iron absorbed into the body. This reduces the effectiveness of iron supplements. Ascorbic acid (vitamin C) increases the absorption of iron, and the antibiotic chloramphenicol increases the blood levels of iron.

Iron affects quite a few drugs. Any drug in the tetracycline family will bind with iron and decrease the absorption of both drugs. Iron interferes with levodopa, methyldopa, etidronate, levothyroxine, penicillamine, and a family of antibiotics called quinolones. Iron decreases the effectiveness of all of these medications.

Eggs, milk, coffee, and tea can decrease the absorption of iron-containing products. Do not take iron within two hours of eating these foods. Fiber, tannin (found in tea), and oxalic acid (found in some vegetables) interfere with iron absorption.

Additional information

Genetic hemochromatosis is a relatively common condition in which the body stores excessive amounts of iron. Over many years, the accumulation leads to cirrhosis of the liver and damage to other organs. Typically, symptoms do not appear until after age 40. This disease is seen almost ten times as often in men (about 1.5 per 1,000) than women, since women tend to lose excess iron through menstruation. Because of this, men should be extremely careful about taking any iron supplements. A healthy diet will usually supply a man with adequate iron.

Click here for a list of reputable websites with general information on nutrition.