Recommendations for iron are provided in the Dietary Reference Intakes (DRIs) developed by the Institute of Medicine of the National Academy of Sciences.¹ Dietary Reference Intakes is the general term for a set of reference values used for planning and assessing nutrient intake for healthy people. Three important types of reference values included in the DRIs are Recommended Dietary Allowances (RDA), Adequate Intakes (AI), and Tolerable Upper Intake Levels (UL).

The RDA recommends the average daily intake that is sufficient to meet the nutrient requirements of nearly all (97-98%) healthy individuals in each age and gender group.² An AI is set when there is insufficient scientific data available to establish a RDA. AIs meet or exceed the amount needed to maintain a nutritional state of adequacy in nearly all members of a specific age and gender group. The UL, on the other hand, is the maximum daily intake unlikely to result in adverse health effects.³ Table 3 lists the RDAs for iron, in milligrams, for infants, children and adults.

Table 3: Recommended Dietary Allowances for Iron for Infants (7 to 12 months), Children, and Adults⁴

Age	Males (mg/day)	Females (mg/day)	Pregnancy (mg/day)	Lactation (mg/day)
7 to 12 months	11	11	N/A	N/A
1 to 3 years	7	7	N/A	N/A
4 to 8 years	10	10	N/A	N/A
9 to 13 years	8	8	N/A	N/A
14 to 18 years	11	15	27	10
19 to 50 years	8	18	27	9
51+ years	8	8	N/A	N/A

Healthy full term infants are born with a supply of iron that lasts for 4 to 6 months. There is not enough evidence available to establish a RDA for iron for infants from birth through 6 months of age. Recommended iron intake for this age group is based on an Adequate Intake (AI) that reflects the average iron intake of healthy infants fed breast milk.⁵ Table 4 lists the AI for iron, in milligrams, for infants up to 6 months of age.

Table 4: Adequate Intake for Iron for Infants (0 to 6 months)⁶

Age (months)	Males and Females (mg/day)
0 to 6	0.27

Iron in human breast milk is well absorbed by infants. It is estimated that infants can use greater than 50% of the iron in breast milk as compared to less than 12% of the iron in infant formula.⁷ The amount of iron in cow's milk is low, and infants poorly absorb it. Feeding cow's milk to infants also may result in gastrointestinal bleeding. For these reasons, cow's milk should not be fed to infants until they are at least 1 year old.⁸ The American Academy of Pediatrics (AAP) recommends that infants be exclusively breast fed for the first six months of life.  

Gradual introduction of iron-enriched solid foods should complement breast milk from 7 to 12 months of age.⁹ Infants weaned from breast milk before 12 months of age should receive iron-fortified infant formula.¹⁰ Infant formulas that contain from 4 to 12 milligrams of iron per liter are considered iron-fortified.¹¹

Data from the National Health and Nutrition Examination Survey (NHANES) describe dietary intake of Americans 2 months of age and older. NHANES (1988-94) data suggest that males of all racial and ethnic groups consume recommended amounts of iron. However, iron intakes are generally low in females of childbearing age and young children.^12 13

Researchers also examine specific groups within the NHANES population. For example, researchers have compared dietary intakes of adults who consider themselves to be food insufficient (and therefore have limited access to nutritionally adequate foods) to those who are food sufficient (and have easy access to food). Older adults from food insufficient families had significantly lower intakes of iron than older adults who are food sufficient. In one survey, twenty percent of adults age 20 to 59 and 13.6% of adults age 60 and older from food insufficient families consumed less than 50% of the RDA for iron, as compared to 13% of adults age 20 to 50 and 2.5% of adults age 60 and older from food sufficient families.¹⁴

Iron intake is negatively influenced by low nutrient density foods, which are high in calories but low in vitamins and minerals. Sugar sweetened sodas and most desserts are examples of low nutrient density foods, as are snack foods such as potato chips. Among almost 5,000 children and adolescents between the ages of 8 and 18 who were surveyed, low nutrient density foods contributed almost 30% of daily caloric intake, with sweeteners and desserts jointly accounting for almost 25% of caloric intake. Those children and adolescents who consumed fewer "low nutrient density" foods were more likely to consume recommended amounts of iron.¹⁵

Data from The Continuing Survey of Food Intakes by Individuals (CSFII1994-6 and 1998) was used to examine the effect of major food and beverage sources of added sugars on micronutrient intake of U.S. children aged 6 to 17 years. Researchers found that consumption of presweetened cereals, which are fortified with iron, increased the likelihood of meeting recommendations for iron intake. On the other hand, as intake of sugar-sweetened beverages, sugars, sweets, and sweetened grains increased, children were less likely to consume recommended amounts of iron.¹⁶

Iron supplementation is indicated when diet alone cannot restore deficient iron levels to normal within an acceptable timeframe. Supplements are especially important when an individual is experiencing clinical symptoms of iron deficiency anemia.

The goals of providing oral iron supplements are to supply sufficient iron to restore normal storage levels of iron and to replenish hemoglobin deficits. When hemoglobin levels are below normal, physicians often measure serum ferritin, the storage form of iron.

A serum ferritin level less than or equal to 15 micrograms per liter confirms iron deficiency anemia in women, and suggests a possible need for iron supplementation.¹⁷

Supplemental iron is available in two forms: ferrous and ferric. Ferrous iron salts (ferrous fumarate, ferrous sulfate, and ferrous gluconate) are the best absorbed forms of iron supplements. ¹⁸

Elemental iron is the amount of iron in a supplement that is available for absorption. Figure 1 lists the percent elemental iron in these supplements.¹⁹ 

The amount of iron absorbed decreases with increasing doses. For this reason, it is recommended that most people take their prescribed daily iron supplement in two or three equally spaced doses. For adults who are not pregnant, the CDC recommends taking 50 mg to 60 mg of oral elemental iron (the approximate amount of elemental iron in one 300 mg tablet of ferrous sulfate) twice daily for three months for the therapeutic treatment of iron deficiency anemia.²⁰ However, physicians evaluate each person individually, and prescribe according to individual needs.

Therapeutic doses of iron supplements, which are prescribed for iron deficiency anemia, may cause gastrointestinal side effects such as nausea, vomiting, constipation, diarrhea, dark colored stools, and/or abdominal distress.²¹

Starting with half the recommended dose and gradually increasing to the full dose will help minimize these side effects. Taking the supplement in divided doses and with food also may help limit these symptoms. Iron from enteric coated or delayed-release preparations may have fewer side effects, but is not as well absorbed and not usually recommendedl.²²

Physicians monitor the effectiveness of iron supplements by measuring laboratory indices, including reticulocyte count (levels of newly formed red blood cells), hemoglobin levels, and ferritin levels. In the presence of anemia, reticulocyte counts will begin to rise after a few days of supplementation. Hemoglobin usually increases within 2 to 3 weeks of starting iron supplementation.

In rare situations parenteral iron (provided by injection or I.V.) is required. Doctors will carefully manage the administration of parenteral iron.²³

Iron deficiency is uncommon among adult men and postmenopausal women. These individuals should only take iron supplements when prescribed by a physician because of their greater risk of iron overload.

Iron overload is a condition in which excess iron is found in the blood and stored in organs such as the liver and heart. Iron overload is associated with several genetic diseases including hemochromatosis, which affects approximately 1 in 250 individuals of northern European descent.²⁴

Individuals with hemochromatosis absorb iron very efficiently, which can result in a build up of excess iron and can cause organ damage such as cirrhosis of the liver and heart failure.^{25 26 27 28 29}

Hemochromatosis is often not diagnosed until excess iron stores have damaged an organ. Iron supplementation may accelerate the effects of hemochromatosis, an important reason why adult men and postmenopausal women who are not iron deficient should avoid iron supplements. Individuals with blood disorders that require frequent blood transfusions are also at risk of iron overload and are usually advised to avoid iron supplements.

Nutrient requirements increase during pregnancy to support fetal growth and maternal health. Iron requirements of pregnant women are approximately double that of non-pregnant women because of increased blood volume during pregnancy, increased needs of the fetus, and blood losses that occur during delivery.³⁰ If iron intake does not meet increased requirements, iron deficiency anemia can occur. Iron deficiency anemia of pregnancy is responsible for significant morbidity, such as premature deliveries and giving birth to infants with low birth weight.^{31 32 33 34 35 36}  

Low levels of hemoglobin and hematocrit may indicate iron deficiency. Hemoglobin is the protein in red blood cells that carries oxygen to tissues. Hematocrit is the proportion of whole blood that is made up of red blood cells. Nutritionists estimate that over half of pregnant women in the world may have hemoglobin levels consistent with iron deficiency. In the U.S., the Centers for Disease Control (CDC) estimated that 12% of all women age 12 to 49 years were iron deficient in 1999-2000. When broken down by groups, 10% of non-Hispanic white women, 22% of Mexican-American women, and 19% of non-Hispanic black women were iron deficient. Prevalence of iron deficiency anemia among lower income pregnant women has remained the same, at about 30%, since the 1980s.³⁷

The RDA for iron for pregnant women increases to 27 mg per day. Unfortunately, data from the 1988-94 NHANES survey suggested that the median iron intake among pregnant women was approximately 15 mg per day.³⁸ When median iron intake is less than the RDA, more than half of the group consumes less iron than is recommended each day.

Several major health organizations recommend iron supplementation during pregnancy to help pregnant women meet their iron requirements. The CDC recommends routine low-dose iron supplementation (30 mg/day) for all pregnant women, beginning at the first prenatal visit.³⁹ When a low hemoglobin or hematocrit is confirmed by repeat testing, the CDC recommends larger doses of supplemental iron. The Institute of Medicine of the National Academy of Sciences also supports iron supplementation during pregnancy.⁴⁰ Obstetricians often monitor the need for iron supplementation during pregnancy and provide individualized recommendations to pregnant women.

Related Links: What is iron? | What foods provide iron? | How much iron do I need? | What happens if I do not get enough iron? | Do I need extra iron? | What are some of the current issues and controversies about iron? |

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Reasonable care has been taken in preparing this document and the information provided herein is believed to be accurate. However, this information is not intended to constitute an "authoritative statement" under Food and Drug Administration rules and regulations.

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The mission of the Office of Dietary Supplements (ODS) is to strengthen knowledge and understanding of dietary supplements by evaluating scientific information, stimulating and supporting research, disseminating research results, and educating the public to foster an enhanced quality of life and health for the U.S. population.

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The information is not intended to be a substitute for professional medical advice. It is important to seek the advice of a physician about any medical condition or symptom. It is also important to seek the advice of a physician, registered dietitian, pharmacist, or other qualified health professional about the appropriateness of taking dietary supplements and their potential interactions with medications.

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Footnotes

1. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
2. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
3. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
4. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
5. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
6. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
7. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
8. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
9. Breastfeeding and the use of human milk. American Academy of Pediatrics. Work Group on Breastfeeding. Pediatrics 1997;100:1035-9. [PubMed abstract] [↩]
10. Breastfeeding and the use of human milk. American Academy of Pediatrics. Work Group on Breastfeeding. Pediatrics 1997;100:1035-9. [PubMed abstract] [↩]
11. American Academy of Pediatrics: Committee on Nutrition. Iron fortification of infant formulas. Pediatrics 1999;104:119-23. [PubMed abstract] [↩]
12. Bialostosky K, Wright JD, Kennedy-Stephenson J, McDowell M, Johnson CL. Dietary intake of macronutrients, micronutrients and other dietary constituents: United States 1988-94. Vital Heath Stat. 11(245) ed: National Center for Health Statistics, 2002:168. [PubMed abstract] [↩]
13. Interagency Board for Nutrition Monitoring and Related Research. Third Report on Nutrition Monitoring in the United States. Washington, DC: U.S. Government Printing Office, J Nutr. 1996;126:iii-x: 1907S-36S. [↩]
14. Dixon LB, Winkleby MA, Radimer KL. Dietary intakes and serum nutrients differ between adults from food insufficient and food sufficient families: Third National Health and Nutrition Examination. J Nutr 2001;131:1232-46. [PubMed abstract] [↩]
15. Kant A. Reported consumption of low-nutrient-density foods by American children and adolescents. Arch Pediatr Aolesc Med 1993;157:789-96. [↩]
16. Frary CD, Johnson RK, Wang MQ. Children and adolescents’ choice of foods and beverages high in added sugars are associated with intakes of key nutrients and food groups. J Adolesc Health 2004;34:56-63. [PubMed abstract] [↩]
17. CDC Recommendations to prevent and control iron deficiency in the United States. Centers for Disease Control and Prevention. MMWR Recomm Rep 1998;47:1-29. [↩]
18. Hoffman R, Benz E, Shattil S, Furie B, Cohen H, Silberstein L, McGlave P. Hematology: Basic Principles and Practice, 3rd ed. ch 26: Disorders of Iron Metabolism: Iron deficiency and overload. Churchill Livingstone, Harcourt Brace & Co, New York, 2000. [↩]
19. Drug Facts and Comparisons. St. Louis: Facts and Comparisons, 2004. [↩]
20. CDC Recommendations to prevent and control iron deficiency in the United States. Centers for Disease Control and Prevention. MMWR Recomm Rep 1998;47:1-29. [↩]
21. CDC Recommendations to prevent and control iron deficiency in the United States. Centers for Disease Control and Prevention. MMWR Recomm Rep 1998;47:1-29. [↩]
22. Hoffman R, Benz E, Shattil S, Furie B, Cohen H, Silberstein L, McGlave P. Hematology: Basic Principles and Practice, 3rd ed. ch 26: Disorders of Iron Metabolism: Iron deficiency and overload. Churchill Livingstone, Harcourt Brace & Co, New York, 2000. [↩]
23. Kumpf VJ. Parenteral iron supplementation. Nutr Clin Pract 1996;11:139-46. [PubMed abstract] [↩]
24. Burke W, Cogswell ME, McDonnell SM, Franks A. Public Health Strategies to Prevent the Complications of Hemochromatosis. Genetics and Public Health in the 21st Centry: using genetic information to improve health and prevent disease. Oxford University Press, 2000. [↩]
25. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
26. Bothwell TH, Charlton RW, Cook JD, Finch CA. Iron Metabolism in Man. St. Louis: Oxford: Blackwell Scientific, 1979. [↩]
27. Burke W, Cogswell ME, McDonnell SM, Franks A. Public Health Strategies to Prevent the Complications of Hemochromatosis. Genetics and Public Health in the 21st Centry: using genetic information to improve health and prevent disease. Oxford University Press, 2000. [↩]
28. Bothwell TH, MacPhail AP. Hereditary hemochromatosis: etiologic, pathologic, and clinical aspects. Semin Hematol 1998;35:55-71. [PubMed abstract] [↩]
29. Brittenham GM. New advances in iron metabolism, iron deficiency, and iron overload. Curr Opin Hematol 1994;1:101-6. [PubMed abstract] [↩]
30. Tapiero H, Gate L, Tew KD. Iron: deficiencies and requirements. Biomed Pharmacother. 2001;55:324-32. [PubMed abstract] [↩]
31. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
32. Cogswell ME, Parvanta I, Ickes L, Yip R, Brittenham GM. Iron supplementation during pregnancy, anemia, and birth weight: a randomized controlled trial. Am J Clin Nutr 2003;78:773-81. [PubMed abstract] [↩]
33. Blot I, Diallo D, Tchernia G. Iron deficiency in pregnancy: effects on the newborn. Curr Opin Hematol 1999;6:65-70. [PubMed abstract] [↩]
34. Malhotra M, Sharma JB, Batra S, Sharma S, Murthy NS, Arora R. Maternal and perinatal outcome in varying degrees of anemia. Int J Gynaecol Obstet 2002;79:93-100. [PubMed abstract] [↩]
35. Allen LH. Pregnancy and iron deficiency: unresolved issues. Nutr Rev 1997;55:91-101. [PubMed abstract] [↩]
36. Iron deficiency anemia: recommended guidelines for the prevention, detection, and management among U.S. children and women of childbearing age. Washington, DC: Institute of Medicine. Food and Nutrition Board.National Academy Press, 1993. [↩]
37. Cogswell ME, Kettel-Khan L, Ramakrishnan U. Iron supplement use among women in the United States: science, policy and practice. J Nutr 2003:133:1974S-7S. [PubMed abstract] [↩]
38. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]
39. CDC Recommendations to prevent and control iron deficiency in the United States. Centers for Disease Control and Prevention. MMWR Recomm Rep 1998;47:1-29. [↩]
40. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium and Zinc. Washington, DC: National Academy Press, 2001. [↩]