Iron is an essential component of hemoglobin, the protein in red blood cells that carries oxygen from the lungs to the rest of the body. Anemia is a deficiency of red blood cells and is diagnosed by a low hemoglobin level in the blood. Iron deficiency anemia develops when the body does not have enough iron to make hemoglobin and red blood cells. It is corrected by replacing iron. Oral iron supplements are an effective, convenient and inexpensive therapy.
Types
Ferrous sulfate, ferrous gluconate and ferrous fumarate are the most common types of supplements. They differ in elemental iron, which is the actual iron content. For example, a ferrous sulfate tablet contains 65 mg elemental iron, in comparison to 36 mg in a ferrous gluconate tablet. Iron is available in different formulations, including enteric coated and delayed-release tablets, capsules, and as a liquid.
Iron Absorption
Iron is best absorbed in the first part of the small intestine. Absorption is greatest on an empty stomach, but is enhanced by vitamin C. Many foods and medicines impair absorption. As a result, taking one iron tablet daily on an empty stomach is as effective as three tablets a day taken with food. The optimal time to take iron is between meals or at bedtime, and at least two hours before or after antacids or calcium supplements.
Dose
The recommended treatment for iron deficiency anemia is 150 mg to 200 mg of elemental iron daily, in divided doses. For example, a ferrous sulfate tablet taken three times a day provides a total daily dose of 195 mg of iron. There is no evidence that one particular form of iron is more effective for correcting iron deficiency. Although 200 mg of iron a day produces the most rapid response, a lower dose will eventually replace iron stores. A study in the "American Journal of Medicine" in 2005 showed that 15 mg of iron per day was as effective as 150 mg in older patients with iron deficiency anemia.
Response
Symptoms of iron deficiency anemia such as fatigue, weakness and headaches, often improve during the first week of treatment. Pica, an abnormal craving for non-food items such as ice, disappears almost as soon as therapy is begun. Uncommon symptoms such as a sore tongue or brittle nails may take three months to fully resolve.
The earliest response in the blood is an increased number of newly produced red blood cells called reticulocytes by the fifth day of treatment. The hemoglobin level begins to rise within two weeks, returning to normal after two months. Iron supplements should be continued for three to six months after correction of anemia to fully replace iron stores.
Side Effects
Side effects involving the gastrointestinal tract occur in 25 percent of people taking standard dose iron supplements. Nausea, heartburn and bloating are due to the non-absorbed iron irritating the stomach and intestines. Abdominal cramping, diarrhea and constipation are common. Stools usually turn dark green or black, a harmless side effect also caused by non-absorbed iron.
The frequency of side effects with ferrous sulfate, gluconate and fumarate supplements is similar when the dose of elemental iron is the same. Side effects are directly related to the amount of iron released in the gastrointestinal tract, and are more severe with high dose supplements.
Solutions
Gastrointestinal symptoms are less likely to develop when the iron dose is gradually increased over several days to weeks. Taking iron with or immediately after meals reduces absorption, but often improves tolerance. Since most side effects are dose-related, switching to a supplement with less iron may eliminate them. The 2005 study in the "American Journal of Medicine" showed that side effects were tree times more common with 150 mg than with 15 mg of iron a day. Taking iron with food or reducing the dose will slow the rate of response and prolong the course of therapy.
Increased fluid and fiber intake combined with stool softeners relieves constipation. Enteric coated and delayed release iron supplements may cause fewer side effects. However, these formulations release iron farther down in the intestinal tract, where it is not well absorbed. Iron can be infused directly into a vein in those rare patients who are intolerant of even low doses of iron.
References
- "Wintrobe's Clinical Hematology"; JP Greer, J Foerster, JN Lukins, GM Rodgers, F Paraskevas and B Glader, Eds.; 11th Edition 2004; Chapter 28
- "The American Journal of Medicine"; Are We Giving Too Much Iron? Low-Dose Iron Therapy is Effective in Octogenarians; E Rimon, N Kagansky, M Kagansky, L Mechnick, T Mashiah, M Namir and S Levy; Volume 118 pg 1142-1147; 2005
- "Acta Med Scand Supplement"; Side Effects of Oral Iron Therapy; L Hallberg, L Ryttinger and L Solvell; Volume 459 pg 3-10; 1966
- "World Journal of Gastroenterology"; Treatment of Iron Deficiency Anemia Associated with Gastrointestinal Tract Diseases; Volume 16 pg 2720-2725; 2010
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