What Is Iron?

Benefits, Side Effects, Dosage, and Interactions

Iron is one of the minerals most vital to human health. While all human cells contain iron, it is mostly found in red blood cells. The health benefits of managing iron levels include eliminating fatigue and many of its sources. Iron also plays a vital role in immune system function, treating anemia, boosting hemoglobin, and much more. 

Iron overdoses are rare. Most of the time, if there is more iron in the body than necessary, the body will save it for future use. Most people get all the iron they need from their diets, but certain illnesses may make it necessary to use iron supplements. 

Health benefits of iron
Verywell / JR Bee 

What Is Iron Used For?

Treats Anemia

Iron is helpful for treating anemia, one of the most common nutritional deficiencies in the world. Anemia results when hemoglobin is below normal ranges. Symptoms of anemia include fatigue, dizziness, shortness of breath, fast heart rate, and an overall feeling of sickness and weakness.  

Boosts Hemoglobin 

The chief function of iron is to form hemoglobin, a red blood cell protein whose main purpose is to transport oxygen in the blood. Additional hemoglobin is important, because humans lose blood in many ways, especially from injuries. Women lose blood every month during their menstrual cycles, which is one of the reasons women may be more likely to suffer from anemia.

Reduces Fatigue 

Iron may help manage unexplained fatigue, which can affect both men and women. Even in someone who isn’t anemic, low iron can still reduce energy levels. This is especially common in women during their reproductive years.

Fatigue from iron deficiency involves more than just a normal level of sleepiness. It causes tiredness that interferes with a person's daily routine, and activities may feel exhausting and less enjoyable.

People with low iron experience fatigue lasting several weeks or longer. Iron-rich foods and supplements can help raise iron levels and eliminate feelings of tiredness and exhaustion. Cooking on cast iron can also add to increased dietary intake.

Improves Muscle Endurance

Muscle metabolism and low iron are linked. Adequate levels of iron help provide the necessary oxygen for muscle contraction and endurance. (Muscle weakness is one of the most common signs of anemia.)

Low iron also makes muscles fatigue easier. A lack of iron will leave muscle tissues inflamed, causing pain. Iron-rich hemoglobin helps to reduce pain, because it repairs affected tissues.

Boosts Immunity 

Iron plays an important role in strengthening the immune system. It promotes hemoglobin, which provides oxygen to damaged cells, tissues, and organs and is necessary for the body's ability to fight diseases and infections. Therefore, low iron status can impair immune function and the healing process.

Improves Concentration             

Research shows that cognitive levels drop with iron deficiency. When iron levels in the blood drop, concentration and attentiveness are affected almost immediately. Getting iron levels restored to a normal range can improve concentration and boost cognitive performance.

Reduces Bruising

People who bruise easily may be suffering from low iron or an actual iron deficiency. This is because hemoglobin affects the production and function of platelets, which control blood-clotting. Frequent bruising is an indication that internal clotting isn’t working as it should. If low iron is the cause of easy and frequent bruising, then iron supplementation can help.

Restores Sleep 

Research published in 2015 shows a connection between low iron stores and sleep issues, including restless sleep, sleep apnea, and insomnia. Research from 2007 found restless sleep in autistic children can be improved with iron therapy.

Possible Side Effects

Upset stomach is the most common side effect of iron supplements. Constipation is another very common side effect with some forms of iron. The risk of iron overload in a diet is low in most healthy adults. People with certain genetic disorders are at risk for an iron overload if their conditions cause them to absorb more iron from food. 

Iron overload may cause a buildup of iron in the liver and other organs as well as the creation of free radicals that damage cells and tissues. This increases the risk for certain cancers. 

Taking high doses of iron supplements can cause nausea, vomiting, and stomach pains. There are very rare cases of iron overdoses leading to internal bleeding, seizure, coma, and even death. 

Iron supplements can decrease the effects of certain medications, including those for treating restless leg syndrome and thyroid problems. Reflux disease medications can reduce the amount of iron that the body absorbs from food and supplements. It is always important to discuss with a healthcare provider whether you should take an iron supplement, especially if you take any prescription medication.

Dosage and Preparation 

The recommended doses for oral iron supplementation for most adults range from 8 milligrams (mg) to 27 mg. The higher doses usually apply to pregnant women and people who are iron-deficient. Iron supplements should be taken with food.

Other Questions

What is the best way to achieve optimal levels of iron?

The best way to achieve optimal levels of iron is through diet rather than supplements. This minimizes the risk of overdose and ensures good iron intake along with other nutrients.  What you pair iron with also matters: vitamin C enhances iron absorption, while calcium and tannins (such as those found in tea and coffee) limit absorption.

Is it dangerous to take iron supplements if I am not anemic?

Anyone considering an iron supplement should talk to a healthcare provider. It is possible that a person could attribute symptoms to an iron deficiency when the symptoms are actually related to another health condition. Excess iron can be dangerous, and iron supplements are only recommended in cases of diagnosed deficiency or when someone is at high risk for a deficiency. 

A Word From Verywell 

Iron is an essential mineral in the human body. Regulating iron levels is important for reducing fatigue, treating anemia, and boosting immunity, among many other health benefits. However, it is important to not take an iron supplement unless you are iron-deficient—speak with your healthcare provider if you feel you are experiencing iron deficiency. Your symptoms could be related to another health condition.

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10 Sources
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  1. Abbaspour N, Hurrell R, Kelishadi R. Review on iron and its importance for human healthJ Res Med Sci. 2014;19(2):164–174.

  2. National Heart, Lung, and Blood Institute. Iron-Deficiency Anemia.

  3. Vaucher P, Druais PL, Waldvogel S, Favrat B. Effect of iron supplementation on fatigue in nonanemic menstruating women with low ferritin: a randomized controlled trial. CMAJ. 2012;184(11):1247-54. doi:10.1503/cmaj.110950

  4. Stugiewicz M, Tkaczyszyn M, Kasztura M, Banasiak W, Ponikowski P, Jankowska EA. The influence of iron deficiency on the functioning of skeletal muscles: experimental evidence and clinical implications. Eur J Heart Fail. 2016;18(7):762-73. doi:10.1002/ejhf.467

  5. Cherayil BJ. The role of iron in the immune response to bacterial infectionImmunol Res. 2011;50(1):1–9. doi:10.1007/s12026-010-8199-1

  6. Jáuregui-lobera I. Iron deficiency and cognitive functions. Neuropsychiatr Dis Treat. 2014;10:2087-95. doi:10.2147/NDT.S72491

  7. Cleveland Clinic. How to Tell If You Have Iron Deficiency Anemia. Updated October 30, 2017.

  8. Murat S, Ali U, Serdal K, et al. Assessment of subjective sleep quality in iron deficiency anaemiaAfr Health Sci. 2015;15(2):621–627. doi:10.4314/ahs.v15i2.40

  9. Dosman CF, Brian JA, Drmic IE, et al. Children with autism: effect of iron supplementation on sleep and ferritin. Pediatr Neurol. 2007;36(3):152-8. doi:10.1016/j.pediatrneurol.2006.11.004

  10. Office of Dietary Supplements. Iron Fact Sheet for Health Professionals. Updated October 16, 2019.