What Is Iron? Identity, Source and Supplement Use

1. Direct Answer

Iron is an essential mineral your body needs to make hemoglobin, the protein in red blood cells that carries oxygen. It also supports energy production, growth and immune function. You get it from foods such as meat, beans and fortified cereals, and from supplements such as ferrous sulfate or ferrous bisglycinate, which are best used when a blood test shows a need.

2. Key Facts Box

Fact	Detail
Name	Iron (chemical symbol Fe)
Type	Essential trace mineral
Main role	Oxygen transport, energy metabolism, DNA synthesis
Body content	About 3–4 g in an adult
Main food sources	Red meat, liver, shellfish, lentils, beans, tofu, fortified cereals
Daily need (US RDA)	Men 8 mg; women 19–50 years 18 mg; pregnancy 27 mg
Upper limit (US)	45 mg per day for adults
Common supplement forms	Ferrous sulfate, ferrous fumarate, ferrous bisglycinate, carbonyl iron
Best known for	Preventing and treating iron deficiency anemia
Key caution	Too much iron is harmful, and overdose is dangerous for children

 

3. Scientific and Common Names

The scientific name of the element is iron, from the Latin word ferrum, which gives the chemical symbol Fe and the atomic number 26. In everyday language it is simply called iron, and on supplement labels it appears as "elemental iron" or as the name of a specific compound.

You may see these names on products:

•       Ferrous sulfate, ferrous fumarate, ferrous gluconate: iron in its ferrous (Fe2+) state, bound to sulfate, fumaric acid or gluconic acid.

•       Ferrous bisglycinate or iron bisglycinate chelate: iron bound to two glycine molecules.

•       Ferric pyrophosphate or ferric citrate: iron in its ferric (Fe3+) state.

•       Heme iron polypeptide: iron from animal hemoglobin.

The word "ferrous" means iron in the Fe2+ state and "ferric" means Fe3+. Both can be absorbed, although ferrous forms are usually absorbed better.

4. Ingredient Category

Iron is a mineral, which means it is an inorganic element and not a vitamin, herb or amino acid. Within minerals it is a trace mineral (also called a microelement), because the body needs it in milligrams per day rather than grams. It is also a transition metal in chemistry, which explains why it moves easily between two charge states and can carry oxygen and transfer electrons.

In nutrition, iron is classed as an essential micronutrient. Essential means the body cannot make it and must obtain it from outside. In regulation, it is a nutrient in foods and supplements, and a medicine when given by injection.

5. Natural Source, Plant Part and Nutrient Form

Iron is not a plant extract, so there is no plant part, leaf, root or seed that defines it. Plants contain iron because they take it up from soil, and animals contain it in their blood and muscle. The nutrient form depends on where it comes from.

Heme iron is part of hemoglobin and myoglobin, so it is found in meat, poultry and fish. The body absorbs about 15–35% of it, and absorption is not greatly affected by other foods.

Non-heme iron is found in plants, eggs, dairy, fortified foods and most supplements. Absorption is lower and more variable, from under 2% to about 20%, depending on how much iron your body has stored and what else is in the meal.

Good plant sources include lentils, chickpeas, beans, tofu, pumpkin seeds, spinach and quinoa. Good animal sources include liver, oysters, clams, sardines and beef. Many breakfast cereals, flours and rice products are fortified with iron as well.

6. Where It Comes From

Iron is formed inside stars and spread through space when massive stars explode. On Earth it is extremely common: the planet is about one third iron by mass, mostly in the core, and iron makes up roughly 5% of the crust, which makes it the fourth most abundant element there. It is mined as ores such as hematite and magnetite.

Iron reaches your plate through soil. Plant roots absorb it, animals eat the plants, and the iron concentrates in seeds, leaves, blood and muscle.

Supplement iron is made industrially. Ferrous sulfate is often a by-product of steel and titanium dioxide production and is then purified. Carbonyl iron is made by decomposing a compound called iron pentacarbonyl. Bisglycinate is made by reacting an iron salt with the amino acid glycine. Heme iron products are made from animal blood.

7. How It Is Used in Supplements

Iron is used in supplements for three main purposes.

1. Treating deficiency. Doctors recommend iron when tests show low ferritin or anemia. This is the best-supported use.

2. Preventing deficiency. Prenatal vitamins, infant drops, and products for people with heavy periods or plant-based diets help meet higher needs.

3. Fortification. Iron is added to flour, rice, salt and cereals to protect whole populations.

Doses on labels are given as elemental iron, meaning the weight of the iron itself. A 325 mg ferrous sulfate tablet, for example, supplies about 65 mg of elemental iron. WHO suggests 30–60 mg of elemental iron per day for prevention in pregnancy and in some high-risk groups, and treatment doses are set by a clinician.

Iron is usually taken in the morning, with water or a vitamin C-rich drink. Tea, coffee, milk and calcium supplements should be kept one to two hours away.

8. Main Active Constituents

Iron has no group of plant compounds to measure. Its activity comes from the iron atom and the molecules that carry or use it.

•       Ferrous iron (Fe2+): the form that crosses the gut wall most easily.

•       Heme: an iron atom inside a ring-shaped molecule, found in hemoglobin and myoglobin.

•       Hemoglobin and myoglobin: carry and store oxygen. About two thirds of body iron sits in hemoglobin.

•       Ferritin: the storage protein. Blood ferritin is the most useful test for body iron stores.

•       Iron-containing enzymes: cytochromes and others that produce cellular energy, make DNA and build neurotransmitters.

•       Hepcidin: a hormone from the liver that controls how much iron the gut absorbs and releases.

9. Why People Research It

People look up iron for practical reasons, and most of them trace back to deficiency, which is the most common nutrient shortfall in the world.

•       Tiredness and weakness. Fatigue, pale skin, breathlessness, cold hands and feet, headaches and brittle nails can all occur with low iron, though they are not specific to it.

•       Heavy periods and pregnancy. Blood loss and the demands of a growing baby raise iron needs sharply.

•       Plant-based diets. Non-heme iron is absorbed less well, so vegetarians are advised to aim for about 1.8 times the usual intake.

•       Sports and training. Endurance athletes can lose iron through sweat, gut bleeding and the effects of hard exercise on hepcidin.

•       Children and teenagers. Rapid growth and brain development make adequate iron especially important.

The strongest evidence supports iron for treating iron deficiency anemia and for preventing anemia in pregnancy and infancy. Taking iron without a deficiency has not been shown to give extra energy.

10. Common Supplement Forms

Form	What it is	Typical features
Ferrous sulfate	Iron salt, about 20% iron	Most studied and affordable; more stomach upset
Ferrous fumarate	Iron salt, about 33% iron	High iron per tablet; similar tolerance to sulfate
Ferrous gluconate	Iron salt, about 12% iron	Often milder; low iron per tablet
Ferrous bisglycinate	Iron bound to glycine	Often better tolerated; good absorption
Carbonyl iron	Fine elemental iron powder	Slow release; lower risk in accidental overdose
Heme iron polypeptide	From animal hemoglobin	Well absorbed; not vegetarian
Liquids, gummies, chewables	Various salts	Check the label; iron content varies
Intravenous iron	Given in a clinic	For severe deficiency or when tablets fail; prescription only

 

Always compare products by elemental iron per serving and not by the tablet weight. Enteric-coated or slow-release products may upset the stomach less but can deliver less absorbed iron.

11. What It Is Not / Common Confusion

•       Iron is not a vitamin. It is a mineral. Vitamin C helps you absorb it, and vitamins B12 and folate help make blood, but they are separate nutrients.

•       Iron on a label is not the same as elemental iron. "Ferrous sulfate 325 mg" does not mean 325 mg of iron.

•       Low hemoglobin is not always low iron. Anemia can come from low vitamin B12, folate, chronic disease or inherited conditions such as thalassemia.

•       Ferritin can mislead. Infection and inflammation raise it, so a normal ferritin does not always rule out deficiency.

•       Iron is not a general energy booster. It helps only if you are short of it.

•       "Natural" does not mean safe at any dose. Iron from food or from supplements can still accumulate in people with hemochromatosis.

12. Safety Note

Iron is safe and helpful when used for a confirmed need, but it has real risks.

•       Test first. Ask a clinician for a blood count and ferritin before starting, and again after about two months of treatment.

•       Keep it away from children. Iron is a leading cause of fatal poisoning in children under six. Store all iron products, including prenatal vitamins and gummies, out of reach. If a child swallows any, call poison control or emergency services at once.

•       Do not exceed the upper limit. The US upper limit is 45 mg per day for adults, unless a doctor directs more.

•       Avoid it if you have iron overload. People with hemochromatosis, thalassemia major or repeated transfusions should not take iron unless a specialist advises it.

•       Expect mild side effects. Nausea, constipation, diarrhea and stomach pain are common. Lower doses, alternate-day dosing or taking it with food often help.

•       Mind the medicines. Iron can reduce absorption of levothyroxine, some antibiotics and other drugs, so separate them as your pharmacist advises.

This page is educational and does not replace medical advice.

13. Frequently Asked Questions

What does iron do in the body?

Iron builds hemoglobin so red blood cells can carry oxygen, supports muscle oxygen storage, powers energy production in cells, and is needed for DNA synthesis, brain development and immune function.

How much iron do I need each day?

The US recommended intake is 8 mg for men and for women over 50, 18 mg for women aged 19–50 and 27 mg during pregnancy. Vegetarians may need about 1.8 times as much.

What foods are high in iron?

Liver, oysters, clams, red meat, sardines, lentils, beans, tofu, pumpkin seeds, spinach and fortified cereals. Pairing plant sources with vitamin C foods improves absorption.

What is the difference between heme and non-heme iron?

Heme iron comes from animal foods and is absorbed more efficiently. Non-heme iron comes from plants, dairy, eggs, fortified foods and most supplements, and its absorption varies more.

Which iron supplement form is best?

Ferrous salts are the most studied and are usually first choice. Ferrous bisglycinate is often better tolerated. Intravenous iron is used when tablets fail. The best option depends on your test results, tolerance and clinician advice.

Can I take too much iron?

Yes. Excess iron can cause poisoning in the short term and organ damage over time, especially in people with hemochromatosis.

14. References

1. National Institutes of Health, Office of Dietary Supplements. Iron: fact sheet for health professionals.

2. Institute of Medicine. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academies Press; 2001.

3. Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;372:1832–1843.

4. Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021;397:233–248.

5. Ganz T. Systemic iron homeostasis. Physiol Rev. 2013;93:1721–1741.

6. Hurrell R, Egli I. Iron bioavailability and dietary reference values. Am J Clin Nutr. 2010;91:1461S–1467S.

7. Stoffel NU, Cercamondi CI, Brittenham G, et al. Iron absorption from oral iron supplements given on consecutive versus alternate days. Lancet Haematol. 2017;4:e524–e533.

8. Peña-Rosas JP, De-Regil LM, Garcia-Casal MN, Dowswell T. Daily oral iron supplementation during pregnancy. Cochrane Database Syst Rev. 2015;(7):CD004736.

9. World Health Organization. Guideline on use of ferritin concentrations to assess iron status in individuals and populations. 2020.

10. World Health Organization. Guideline: daily iron supplementation in adult women and adolescent girls. 2016.

11. Saper RB, et al. Lead, mercury, and arsenic in US- and Indian-manufactured Ayurvedic medicines sold via the Internet. JAMA. 2008;300:915–923.

12. Kowdley KV, et al. ACG clinical guideline: hereditary hemochromatosis. Am J Gastroenterol. 2019;114:1202–1218.

13. US FDA. 21 CFR 101.17(e) and 21 CFR 310.518 (iron warning statement and unit-dose packaging).