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BackgroundReturn to top

Iron is an essential mineral and an important component of proteins involved in oxygen transport and metabolism. Iron is also an essential cofactor in the synthesis of neurotransmitters such as dopamine, norepinephrine, and serotonin. About 15 percent of the body's iron is stored for future needs and mobilized when dietary intake is inadequate. The body usually maintains normal iron status by controlling the amount of iron absorbed from food.

There are two forms of dietary iron: heme and non-heme. Sources of heme iron include meat fish and poultry. Sources of non-heme iron, which is not absorbed as well as heme iron, include beans, lentils, flours, cereals, and grain products. Other sources of iron include dried fruit, peas, asparagus, leafy greens, strawberries, and nuts.

The World Health Organization considers iron deficiency to be the largest international nutritional disorder. Although much of the ethnic disparity in iron deficiency anemia remains unexplained, socioeconomic factors may be involved.

Iron deficiency can be determined by measurement of iron levels within the body, mainly serum ferritin levels, which can also help distinguish between iron deficiency anemia and anemia associated with chronic disease.

Herbal preparations such as yellow dock root may be used in iron deficiency, although scientific evidence may be lacking.

SynonymsReturn to top

Atomic number 26, carbonyl iron, dextran-iron, elemental Iron, FE, Fer, ferrous carbonate anhydrous, ferrous fumarate, ferrous gluconate, ferrous pyrophosphate, ferrous sulfate, iron dextran, iron-polysaccharide, iron sorbitol, Iron sucrose, sodium ferric gluconate.

Selected U.S. brand names: DexFerrum®, Femiron®, Feosol Caplets®, Feosol Tablets®, Feostat®, Feostat Drops®, Feratab®, Fer-gen-sol®, Fergon®, Fer-In-Sol Drops®, Fer-In-Sol Syrup®, Fer-Iron Drops®, Fero-Gradumet®, Ferospace®, Ferralet®, Ferralet Slow Release®, Ferralyn Lanacaps®, Ferra-TD®, Ferretts®, Ferrlecit®, Fumasorb®, Fumerin®, Hemocyte®, Hemofer®, Hytinic®, InFeD®, Ircon®, Mol-Iron®, Nephro-Fer®, Niferex®, Niferex-150®, Nu-Iron®, Nu-Iron 150®, Simron®, Slow Fe®, Span-FF®, Venofer®.

EvidenceReturn to top

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Uses based on scientific evidenceGrade*
Anemia of chronic disease

Taking iron orally with epoetin alfa (erythropoietin, EPO, Epogen®, Procrit®) is effective for treating anemia associated with chronic renal failure and chemotherapy.
Iron deficiency anemia

Ferrous sulfate (Feratab®, Fer-Iron®, Slow-FE®) is the standard treatment for treating iron deficiency anemia. Dextran-iron (INFeD®) is given intravenously by healthcare providers to restore adequate iron levels in bone marrow when oral iron therapy has failed.
ACE inhibitor-associated cough

Taking iron orally seems to inhibit cough associated with angiotensin converting enzyme (ACE) inhibitors, such as captopril (Capoten®), enalapril (Vasotec®), and lisinopril (Prinivil®, Zestril®).
Preventing iron deficiency in menstruating women

Iron supplementation has been shown to improve iron status in menstruating women.
Prevention of iron deficiency anemia in pregnancy

Iron supplements have been shown to help prevent iron deficiency anemia in pregnant women. Anemia in pregnant women is associated with adverse outcomes such as low birth weight, premature birth, and maternal mortality. Screening by a qualified healthcare provider is needed. Low doses are generally well tolerated and associated with better compliance.
Attention deficit hyperactivity disorder (ADHD)

Based on preliminary data, taking iron orally might improve symptoms of attention deficit hyperactivity disorder (ADHD). More study is necessary before a conclusion can be drawn.
Fatigue in women with low ferritin levels

Ferrous sulfate may improve fatigue primarily in women with borderline or low serum ferritin concentrations. Further research is needed to confirm these results.
Improving cognitive performance related to iron deficiency

Taking iron by mouth seems to improve cognitive function related to iron deficiency in iron-deficient children and adolescents. Further research is needed to confirm the potential benefit of iron in this indication. Iron supplements are not recommended for improving cognitive performance in non-iron deficient people.
Lead toxicity

Iron deficiency may increase the risk of lead poisoning in children. However, the use of iron supplementation in lead poisoning should be reserved for those individuals who are truly iron deficient or for those individuals with continuing lead exposure, such as continued residence in lead-exposed housing.
Preventing anemia associated with preterm/low birth weight infants

Further study of prenatal iron supplementation is needed before a firm recommendation can be made regarding the effects of anemia on preterm/low birth weight infants.
Preventing iron deficiency in exercising women

Preliminary studies suggest that iron supplementation can reverse mild anemia after exercise, improve energy, and enhance performance. However, other studies disagree. Further research is needed in this area before firm recommendations can be made.
Prevention of iron deficiency after blood donation

The results of early study indicate that elemental iron can adequately compensate for iron loss in males and females who donate whole blood up to four (females) or six times per year (males).
Prevention of iron deficiency anemia due to gastrointestinal bleeding

Intravenous high-dose iron sucrose therapy in patients with iron deficiency anemia due to gastrointestinal blood loss appears to be safe and therefore is a therapeutic option that may save time and improve patient compliance. More study is needed in this area.
Treatment of predialysis anemia

Adequate iron supplementation may be beneficial as an adjunct therapy with erythropoietin in the treatment of predialysis anemia. Predialysis anemia should be treated by a qualified healthcare provider. More study is needed in this area.
Therapy for anemia after orthopedic surgery

Early study reports that iron taken after elective hip or knee replacement surgery does not result in higher hemoglobin after surgery or a faster rate of increase in hemoglobin than placebo.

*Key to grades
A: Strong scientific evidence for this use;
B: Good scientific evidence for this use;
C: Unclear scientific evidence for this use;
D: Fair scientific evidence against this use;
F: Strong scientific evidence against this use.

Grading rationale

Uses based on tradition or theory
The below uses are based on tradition or scientific theories. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.

Anemia in anorexia nervosa, arm tremor, athletic performance enhancement, canker sores, Crohn's disease, cystic fibrosis, depression, enhanced immune function, fatigue, female infertility, growth, menorrhagia (abnormally heavy menstrual bleeding), pagophagia (compulsive eating of ice), prevention of anemia in blood donors, restless leg syndrome.

DosingReturn to top

The below doses are based on scientific research, publications, traditional use, or expert opinion. Many herbs and supplements have not been thoroughly tested, and safety and effectiveness may not be proven. Brands may be made differently, with variable ingredients, even within the same brand. The below doses may not apply to all products. You should read product labels, and discuss doses with a qualified healthcare provider before starting therapy.

Adults (18 years and older)
The Recommended Dietary Allowance (RDA) for males (19- 50 years) is 8 milligrams per day; females (19- 50 years) 18 milligrams per day; adults (51 years and older) 8 milligrams per day; pregnant women (all ages) 27 milligrams per day; breastfeeding women (19 years and older) 9 milligrams per day.

The Tolerable Upper Intake Level (UL) for adults (19 years and older) is 45 milligrams per day.

The RDA for iron from a completely vegetarian diet should be adjusted as follows: 14 milligrams per day for adult men and postmenopausal women, 33 milligrams per day for premenopausal women, and 26 milligrams per day for adolescent girls.

Doses ranging from 60 to 180 milligrams of elemental iron have been used for iron deficiency/anemia. Dextran-iron (INFeD®) is given by healthcare providers to replenish depleted iron stores in the bone marrow where it is incorporated into hemoglobin. The usual adult dose is 2 milliliters per day (100 milligrams iron).

Children (younger than 18 years)
The Recommended Dietary Allowance (RDA) is 11 milligrams for 7-12 months; 7 milligrams for 1-3 years; 10 milligrams for 4-8 years; 8 milligrams for 9-13 years (male and female); 11 milligrams for males 14-18 years; 15 milligrams for females 14-18 years; 27 milligrams for pregnant females 14-18 years; 10 milligrams for breastfeeding females 14-18 years. For infants 0-6 months, 0.27 milligrams is recommended as the adequate intake level (AI), which is used when RDA cannot be determined.

The Tolerable Upper Intake Level (UL) for infants (1-12 months) is not possible to establish; the UL for children (1-13 years) is 40 milligrams per day; the UL for adolescents (14-18 years) is 45 milligrams per day.

Dextran-iron (INFeD®) is an intravenous preparation given by qualified healthcare provider to replenish depleted iron stores in the bone marrow where it is incorporated into hemoglobin. Doses of 50 milligrams iron (1 milliliter) (5-10 kilograms) and 100 milligrams iron (2 milliliters) (10-50 kilograms) have been used.

SafetyReturn to top

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Iron is a trace mineral and hypersensitivity is unlikely. Avoid if known allergy/hypersensitivity to products containing iron.

Side Effects and Warnings
In general, people with a history of kidney disease, intestinal disease, peptic ulcer disease, enteritis, colitis, pancreatitis, hepatitis, who consume excessive alcohol, plan to become pregnant, or are over age 55 and have a family history of heart disease should consult a doctor and pharmacist before taking iron.

Liquid oral iron preparations can possibly blacken teeth.

Acute overdosage or iron accumulation symptoms may include arthritis, signs of gonadal failure (amenorrhea, early menopause, loss of libido, impotence), and shortness of breath/dyspnea. High doses may cause vomiting and diarrhea followed by cardiovascular or metabolic toxicity and death. It is unclear whether high levels are associated with cancer, coronary heart disease, or myocardial infarction (MI or heart attack).

Gastrointestinal upset, including nausea, vomiting, constipation, diarrhea, and dark stools, has been reported. Gastrointestinal side effects are relatively common and corrective bowel regimens such as increasing dietary fiber or over the counter medication might be recommended to balance these side effects. Supervision by a qualified healthcare provider is recommended.

Individuals with blood disorders who require frequent blood transfusions are also at risk of iron overload and should not take iron supplements without direction by a qualified healthcare provider. Long-term use of high doses of iron can cause hemosiderosis that clinically resembles hemochromatosis. Iron overload is associated with several genetic diseases including hemochromatosis (a defect in iron metabolism with build up of iron in the body). The most commonly associated early hemochromatosis symptoms include fatigue, weakness, weight loss, abdominal pain, and arthralgia (joint pain). Iron overload is possible in very low birth weight infants after multiple blood transfusions due to increase liver iron concentration. Prenatal iron-overload might contribute to the pathogenesis of the disease, but further studies are needed to confirm the assumption. Accumulation of excess iron is being investigated as a potential contributor to neurodegenerative diseases such as Alzheimer's and Parkinson's disease.

HCV infection and iron loading may aggravate oxidative stress in dialysis patients.

A case of hypersiderosis (uncontrollable sweating) has been reported with long-term iron supplementation in uremic patients treated with periodic dialysis.

One study indicates that higher consumption of total red meat, especially various processed meats, may increase risk of developing type 2 diabetes in women.

Pregnancy and Breastfeeding
Pregnant or breastfeeding women should seek guidance from a qualified healthcare provider before taking dietary supplements. Iron status of the pregnant woman should be measured early (before the 15th week of gestation) and iron supplements should be given as selective prophylaxis based on the serum ferritin level.

FDA Pregnancy Category B: Usually safe but benefits must outweigh the risks.

FDA Pregnancy Category C: Safety for use during pregnancy has not been established for replenishing depleted iron stores in the bone marrow where it is incorporated into hemoglobin.

InteractionsReturn to top

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs
Acetohydroxamic acid (AHA, Lithostat®) is prescribed to decrease urinary ammonia, and may help with antibiotics to work or help with other kidney stone treatment. Use with iron supplements may cause either medicine to be less effective.

Allopurinol (Zyloprim®), a medication used to treat gout, may increase iron storage in the liver and should not be used in combination with iron supplements.

Aminosalicylic acid (para-aminosalicylic acid, PAS, Paser) may cause a malabsorption syndrome (weight loss, iron and vitamin depletion, excessive fat in the stools (steatorrhea)). A qualified healthcare provider should be contacted immediately if any of these symptoms are experienced.

Antacids may reduce iron absorption and reduced efficacy has occurred occasionally. Clinically significant effects are unlikely with adequate dietary iron intake. However, it is recommended to avoid antacids or separate the doses of antacids and iron.

Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) can cause mucosal damage and bleeding throughout the gastrointestinal tract. Chronic blood loss associated with long-term use of these agents may contribute to iron deficiency anemia. Since iron supplements may also irritate the gastrointestinal tract, patients should not use them concurrently with NSAIDs unless recommended by a physician. Iron rich food intake may be advised as an alternative.

Iron can decrease absorption of prescription drug bisphosphonates by forming insoluble complexes. Bisphosphonates include alendronate (Fosamax®), etidronate (Didronel®), risedronate (Actonel®), and tiludronate (Skelid®). Doses of bisphosphonates should be separated by at least two hours from doses of all other medications, including supplements such as iron.

Chloramphenicol (Chloromycetin®) can reduce the response to iron therapy in iron deficiency anemia.

Cholestyramine (Questran®) and colestipol (Colestid®) may bind iron in the gut, reducing its absorption. Clinically significant iron deficiency induced by these drugs has not been reported and supplements are not likely to be needed. If taking iron supplements for other causes of deficiency, it is recommended that the iron and cholestyramine or colestipol doses be separated by at least four hours.

Desferrioxamine (DFO) is an iron-chelating drug that lowers iron levels.

Iron supplements and dimercaprol may combine in the body to form a harmful chemical.

Bone marrow iron deposits have been shown to decrease significantly in patients on EPO-R.

Iron decreases the absorption of fluoroquinolone antibiotics. Fluoroquinolones include ciprofloxacin (Cipro®), levofloxacin (Levaquin®), ofloxacin (Floxin®), and others. It is recommended to take these antibiotics at least two hours before or two hours after iron-containing supplements.

Gastric acid is important for the absorption of iron, particularly dietary non-heme (plant-derived) iron. Adequate dietary iron intake is recommended when taking H2 blockers like cimetidine (Tagamet®), ranitidine (Zantac®), famotidine (Pepcid®), or nizatidine (Axid®). Iron supplements are not usually required unless they are being used for another indication.

There is some evidence in healthy people that iron forms chelates with levodopa (Sinemet®), reducing the amount of levodopa absorbed by around 50%. Until further research is available, separate doses of levodopa and iron as much as possible.

Iron can decrease the absorption and efficacy of levothyroxine (Levoxyl®, Synthroid®) by forming insoluble complexes in the gastrointestinal tract. It is recommended that levothyroxine and iron doses be separated by at least two hours.

Iron can decrease the absorption of methyldopa (Aldomet®), resulting in increases in blood pressure. It is recommended that methyldopa and iron doses be separated by at least two hours.

Oral iron supplements markedly reduce absorption of mycophenolate mofetil (CellCept®). It is recommended that iron be taken four to six hours before or two hours after mycophenolate mofetil.

There is some evidence that pancreatic enzyme supplements, such as Cotazym®, Creon®, Pancrease®, Ultrase®, and Viokase®, can reduce iron absorption possibly by binding iron or altering pH. Clinical significance is unlikely, except in people with cystic fibrosis who need pancreatic enzyme supplements for prolonged periods and who have other factors contributing to iron deficiency. Iron status should be monitored by a qualified healthcare provider.

Oral iron supplements can reduce absorption of penicillamine (Cuprimine®, Depen®) by 30% to 70%, probably due to chelate formation. Efficacy of penicillamine is reduced in Wilson's disease; the clinical significance in people with rheumatoid arthritis (RA) has not been determined. Patients should be advised to take penicillamine at least two hours before or after iron-containing supplements.

Gastric acid is important for the absorption of iron. However, long-term treatment, up to 12.5 years, with proton pump inhibitors, such as esomeprazole (Nexium®), lansoprazole (Prevacid®), omeprazole (Prilosec®), rabeprazole (Aciphex®), and pantoprazole (Protonix®, Pantoloc®, has not been associated with iron depletion or anemia in people with normal iron stores. Maintaining adequate dietary iron intake is recommended.

Concomitant use can decrease the absorption of tetracycline antibiotics by 50% to 90%. Patients should be advised to take tetracyclines at least two hours before or after iron-containing supplements. Some of these drugs include doxycycline (Vibramycin®), minocycline (Minocin®), tetracycline (Achromycin®), and others.

Interactions with Herbs and Dietary Supplements
Acacia forms an insoluble gel with ferric iron. Clinical significance is unknown.

Calcium supplements have been shown to inhibit absorption of iron supplements when taken with food. However, in people with adequate iron stores, this does not appear to be clinically significant. If at risk for iron deficiency, it is recommended to take calcium supplements at bedtime, instead of with meals, to avoid inhibiting dietary iron absorption.

Copper metabolism may be altered by iron supplements, but the clinical importance of this observation is unknown.

Citric, malic, tartaric, and lactic acids have some enhancing effects on nonheme iron absorption.

Phytic acid is present in legumes, grains, and rice and is an inhibitor of nonheme iron absorption. Small amounts of phytic acid can reduce nonheme iron absorption by 50%. The absorption of iron from legumes, such as soybeans, black beans, lentils, mung beans, and split peas, has been shown to be as low as 2%.

Polyphenols, found in some fruits, vegetables, coffees, teas, wines, and spices, can markedly inhibit the absorption of nonheme iron. This effect is reduced by the presence of vitamin C.

Riboflavin (vitamin B2) supplements may improve the hematological response to iron supplements in some people with anemia.

Based on preliminary data, iron may decrease selenium levels. Further research is needed to confirm these results.

Soy protein reduces the absorption of dietary non-heme (plant-derived) iron, probably due to binding of iron by phytate and calcium present in soy. Fermented soy products seem to inhibit iron absorption less.

Vitamin A appears to be involved in mobilizing iron from tissue stores for delivery to developing red blood cells in the bone marrow. Vitamin A may also be involved in the differentiation and proliferation of blood stem cells in the bone marrow and in the synthesis of erythropoietin. Preliminary evidence also suggests that vitamin A and beta-carotene may enhance non-heme iron absorption from iron-fortified wheat and corn flour and rice. It is unlikely that vitamin A supplements would have significant effects on iron status in people without vitamin A deficiency.

The amount of vitamin C in the diet is a factor in dietary iron absorption and iron status. Vitamin C can counteract the effects of substances, which inhibit iron absorption. Supplemental or dietary vitamin C improves absorption of supplemental or dietary non-heme (plant-derived) iron ingested at the same time. Taking a vitamin C supplement to improve the absorption of dietary or supplemental iron probably is not necessary for most people, especially if their diet contains adequate amounts of vitamin C.

Use of oral iron preparations in premature infants with low serum vitamin E levels may cause hemolysis and hemolytic anemia. Vitamin E deficiency should be corrected before administering supplemental iron.

Iron may decrease zinc absorption but there does not seem to be a clinically significant interaction between dietary iron and zinc or between supplemental iron and zinc dietary sources.

Methodology Return to top

This information is based on a professional level monograph edited and peer-reviewed by contributors to the Natural Standard Research Collaboration ( Ethan Basch, MD (Memorial Sloan-Kettering Cancer Center); Dawn Costa, BA, BS (Natural Standard Research Collaboration); Shaina Tanguay-Colucci, BS (Natural Standard Research Collaboration); Catherine Ulbricht, PharmD (Massachusetts General Hospital); Christine Ulbricht, PharmD (University of Massachusetts); Wendy Weissner, BA (Natural Standard Research Collaboration).

Methodology details

Selected references Return to top

  1. Beard JL. Iron deficiency: assessment during pregnancy and its importance in pregnant adolescents. Am J Clin Nutr 1994;59(2 Suppl):502S-508S.
  2. Black DA, Fraser C. M. Iron deficiency anaemia and aspirin use in old age. Br J Gen Pract 1999;49(446):729-730.
  3. Black MM, Baqui AH, Zaman K, et al. Iron and zinc supplementation promote motor development and exploratory behavior among Bangladeshi infants. Am J Clin Nutr 2004;80(4):903-910.
  4. Bruner AB, Joffe A, Duggan AK, et al. Randomised study of cognitive effects of iron supplementation in non-anaemic iron-deficient adolescent girls. Lancet 10-12-1996;348(9033):992-996.
  5. Campbell NR, Hasinoff BB, Stalts H, et al. Ferrous sulfate reduces thyroxine efficacy in patients with hypothyroidism. Ann Intern Med 12-15-1992;117(12):1010-1013.
  6. Chimonas MA, Baggett HC, Parkinson AJ, et al. Asymptomatic Helicobacter pylori infection and iron deficiency are not associated with decreased growth among Alaska Native children aged 7-11 years. Helicobacter 2006 Jun;11(3):159-67.
  7. Cogswell ME, Parvanta I, Ickes L, et al. Iron supplementation during pregnancy, anemia, and birth weight: a randomized controlled trial. Am J Clin Nutr 2003;78(4):773-781.
  8. Dawson B, Goodman C, Blee T, et al. Iron supplementation: oral tablets versus intramuscular injection. Int J Sport Nutr Exerc Metab 2006 Apr;16(2):180-6.
  9. Makrides M, Crowther CA, Gibson RA, et al. Efficacy and tolerability of low-dose iron supplements during pregnancy: a randomized controlled trial. Am J Clin Nutr 2003;78(1):145-153..
  10. Milman N, Bergholt T, Eriksen L, et al. Iron prophylaxis during pregnancy -- how much iron is needed? A randomized dose- response study of 20-80 mg ferrous iron daily in pregnant women. Acta Obstet Gynecol Scand 2005;84(3):238-247.
  11. Radtke H, Tegtmeier J, Rocker L, et al. Daily doses of 20 mg of elemental iron compensate for iron loss in regular blood donors: a randomized, double-blind, placebo-controlled study. Transfusion 2004;44(10):1427-1432.
  12. Schroder O, Schrott M, Blumenstein I, et al. A study for the evaluation of safety and tolerability of intravenous high-dose iron sucrose in patients with iron deficiency anemia due to gastrointestinal bleeding. Z Gastroenterol 2004;42(8):663-667.
  13. Weatherall M, Maling TJ. Oral iron therapy for anaemia after orthopaedic surgery: randomized clinical trial. ANZ J Surg 2004;74(12):1049-1051.
  14. Zhou SJ, Gibson RA, Crowther CA, et al. Effect of iron supplementation during pregnancy on the intelligence quotient and behavior of children at 4 y of age: long-term follow-up of a randomized controlled trial. Am J Clin Nutr 2006 May;83(5):1112-7.
  15. Zimmermann MB, Muthayya S, Moretti D, et al. Iron fortification reduces blood lead levels in children in Bangalore, India. Pediatrics 2006 Jun;117(6):2014-21.

January 01, 2008.

Natural Standard Logo This evidence-based monograph was prepared by the Natural Standard Research Collaboration. The information provided should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. Talk to your health care provider before taking any prescription or over the counter drugs (including any herbal medicines or supplements) or following any treatment or regimen. Copyright© 2008 Natural Standard ( All Rights Reserved.