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Iron deficiency anemia

What is iron deficiency anemia?

Iron deficiency anemia (IDA) is the most common form of anemia worldwide and occurs when the body lacks sufficient iron to produce healthy red blood cells.1,2 Red blood cells contain hemoglobin—a protein that depends on iron to carry oxygen from the lungs to tissues and organs throughout the body.1,2 Without enough iron, hemoglobin production drops, reducing the blood’s capacity to transport oxygen efficiently. According to the World Health Organization (WHO), non-pregnant adult women with a hemoglobin level below 12 g/dL and adult men with levels below 13 g/dL are considered anemic.3

Iron is essential not only for oxygen transport, but also for storing oxygen, producing energy, and supporting cell growth.1,2 The human body contains approximately 3 to 4 grams of iron—most of which is used in the production of hemoglobin.4 When iron stores are depleted or iron is not adequately absorbed or utilized, the result can be fewer red blood cells in circulation, leading to symptoms such as fatigue, weakness, and shortness of breath.1

Iron deficiency is believed to be the leading cause of anemia globally, though other causes include deficiencies in folic acid or vitamin B12, chronic inflammation, parasitic infections, or disorders affecting red blood cell production.1,2 It’s estimated that more than 2 billion people worldwide are anemic, with over 1 billion affected by iron deficiency anemia.5

  1. Miller JL. Iron deficiency anemia: a common and curable disease. Cold Spring Harb Perspect Med. 2013;3(7):a011866. Published 2013 Jul 1. doi:10.1101/cshperspect.a011866

  2. Camaschella C. Iron deficiency: new insights into diagnosis and treatment. Hematology Am Soc Hematol Educ Program. 2015;2015:8-13. doi:10.1182/asheducation-2015.1.8

  3. World Health Organization. WHO Guideline on Use of Ferritin Concentrations to Assess Iron Status in Individuals and Populations. World Health Organization; 2020.

  4. Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021 Jan 16;397(10270):233-248.

  5. Global Burden of Disease Collaborative Network. Global Burden of Disease Study 2019 (GBD 2019) Results. Seattle, United States: Institute for Health Metrics and Evaluation (IHME); 2020. Available from http://ghdx.healthdata.org/gbd-results-tool.

Facts

An estimated 10 million people in the United States are iron deficient, with 5 million of them living with IDA.1 Globally, anemia impacts roughly one-third of all women of reproductive age, making it the most common and widespread nutritional disorder in the world.2 

While iron deficiency can begin silently, once it advances to IDA, it can have measurable effects on physical and mental health. IDA may contribute to:3-8

  • Increased risk of premature birth during pregnancy

  • Higher incidence of stroke

  • Delayed cognitive and physical development in children

  • Fatigue, poor concentration, and mood changes in adults

  • Cognitive decline and higher dementia risk in older populations

  • Reduced quality of life due to decreased energy and endurance

  • Greater risk of infections due to weakened immune defenses

Because symptoms of iron deficiency anemia often overlap with those of chronic conditions like chronic kidney disease, inflammatory bowel disease, or heart failure, it is frequently overlooked or misattributed to the underlying disease.4

  1. Miller JL. Iron deficiency anemia: a common and curable disease. Cold Spring Harb Perspect Med. 2013;3(7):a011866. Published 2013 Jul 1. doi:10.1101/cshperspect.a011866

  2. World Health Organization. Iron Deficiency Anaemia: Assessment, Prevention and Control. 2001

  3. Doom JR, Georgieff MK, Gunnar MR. Institutional care and iron deficiency increase ADHD symptomology and lower IQ 2.5-5 years post-adoption. Dev Sci. 2015;18(3):484-494. doi:10.1111/desc.12223

  4. Camaschella C. Iron deficiency: new insights into diagnosis and treatment. Hematology Am Soc Hematol Educ Program. 2015;2015:8-13. doi:10.1182/asheducation-2015.1.8

  5. Sachdev H, Gera T, Nestel P. Effect of iron supplementation on mental and motor development in children: systematic review of randomised controlled trials. Public Health Nutr. 2005;8(2):117-132. doi:10.1079/phn2004677

  6. Zage AU, Nas FS, Ali M, Aliyu S. Maternal Anemia and Risk of Neonatal Mortality: A Review. Neonatal. 2024;4(1):16. doi:10.35702/neo.10016

  7. Andro M, Le Squere P, Estivin S, Gentric A. Anaemia and cognitive performances in the elderly: a systematic review. Eur J Neurol. 2013;20(9):1234-1240. doi:10.1111/ene.12175

  8. Thein M, Ershler WB, Artz AS, et al. Diminished quality of life and physical function in community-dwelling elderly with anemia. Medicine (Baltimore). 2009;88(2):107-114. doi:10.1097/MD.0b013e31819d89d5

Symptoms

The most common symptom of iron deficiency anemia (IDA) is fatigue, which can interfere with daily activities and overall functioning.1 Other symptoms include dizziness, shortness of breath, headaches, irregular heartbeat, and cognitive difficulties such as poor concentration and memory.2-4 Because these symptoms are non-specific, they are often mistaken for signs of other conditions—leading to delays in diagnosis and treatment of IDA.

In some cases, individuals may experience cravings for non-food substances like ice or clay—a condition known as pica—which can be a sign of IDA.5

These symptoms result from reduced oxygen delivery to body tissues.6

  1. Haas JD, et al. Maternal anemia and risk of neonatal mortality: a review. J Nutr. 2001;131(2S-2):676S-688S; discussion 688S-690S.

  2. Mayo Clinic. Iron deficiency anemia - Symptoms & causes. Accessed August 6, 2024. https://www.mayoclinic.org/diseases-conditions/iron-deficiency-anemia/symptoms-causes/syc-20355034

  3. Mayo Clinic. Anemia - Symptoms and causes. Accessed August 6, 2024. https://www.mayoclinic.org/diseases-conditions/anemia/symptoms-causes/syc-20351360

  4. Cleveland Clinic. Anemia: Symptoms, Causes & Treatment. Accessed August 6, 2024. https://my.clevelandclinic.org/health/diseases/3929-anemia

  5. Miller JL. Iron deficiency anemia: a common and curable disease. Cold Spring Harb Perspect Med. 2013;3(7):a011866. Published 2013 Jul 1. doi:10.1101/cshperspect.a011866

  6. Ebner N, von Haehling S. Iron deficiency in heart failure: a practical guide. Card Fail Rev. 2019;5(3):173–175.

Causes

Iron deficiency anemia (IDA) is most often the result of untreated or unrecognized iron deficiency.¹ It can arise from several underlying causes, typically involving inadequate iron intake, impaired absorption, or excessive iron loss.

There are two main types of iron deficiency that may lead to anemia:2

  • Absolute iron deficiency, when iron stores are depleted.

  • Functional iron deficiency, when iron stores are present but cannot be properly mobilized for use. 

Common underlying causes of IDA include:2-5

  • Heavy menstrual bleeding

  • Pregnancy, both during and after childbirth

  • Chronic inflammatory diseases, such as heart failure, inflammatory bowel disease, and chronic kidney disease

  • Cancer or cancer-related treatments (e.g., chemotherapy, surgery)

  • Surgical or traumatic blood loss

  • Frequent blood donation

  • Poor dietary iron intake or malabsorption due to gastrointestinal disorders

  1. Miller JL. Iron deficiency anemia: a common and curable disease. Cold Spring Harb Perspect Med. 2013;3(7):a011866.

  2. Dignass A, Farrag K, Stein J. Limitations of serum ferritin in diagnosing iron deficiency in inflammatory conditions. Int J Chronic Dis. 2018;2018:9394060.

  3. Camaschella C. Iron-deficiency anemia. N Engl J Med. 2015;372(19):1832–1843.

  4. Busti F, Campostrini N, Martinelli N, Girelli D. Iron deficiency in the elderly: ready for prime time? Pharmaceuticals (Basel). 2018;11(4):94.

  5. Lopez A, Cacoub P, Macdougall IC, Peyrin-Biroulet L. Iron deficiency anaemia. Lancet. 2016;387(10021):907–916.

Treatment

The primary goal of treating iron deficiency anemia (IDA) is to replenish iron stores and restore hemoglobin to normal levels.1 Appropriate treatment can relieve symptoms such as fatigue, cognitive decline, and poor physical performance, significantly improving a patient’s quality of life.1,2 Successful management depends not only on iron repletion but also on identifying and addressing the underlying cause of iron loss. In patients with chronic conditions, ongoing or repeated iron therapy may be necessary.3-5

Oral iron supplements are commonly used as first-line treatment, particularly in patients with mild or moderate IDA and no signs of malabsorption or ongoing blood loss.6 Oral iron is typically inexpensive and accessible, but:

  • It may take several months to restore iron levels.

  • Gastrointestinal side effects (e.g., constipation, nausea, abdominal discomfort) are common and may limit adherence.

  • Inflammatory conditions can reduce absorption, making oral iron less effective.

IV iron is often used when:1-2

  • Oral iron is poorly tolerated or ineffective.

  • There is a need for rapid correction of anemia.

  • The patient has a chronic inflammatory condition (e.g., IBD, CKD, heart failure) that impairs iron absorption or mobilization.

IV iron bypasses the gastrointestinal tract and allows for direct replenishment of iron stores, often with fewer administrations and faster improvement in hemoglobin levels.1-2

  1. Jimenez K, Kulnigg-Dabsch S, Gasche C. Management of iron deficiency anemia. Gastroenterol Hepatol (N Y). 2015;11(4):241–250.

  2. Strauss WE, Auerbach M. Safety and efficacy of intravenous iron therapy in patients with iron-deficiency anemia: a systematic review. Patient Relat Outcome Meas. 2018;9:285–298.

  3. Johns Hopkins Medicine. Iron-deficiency anemia. Johns Hopkins Medicine; [cited 2024 Aug 6]. Available from: https://www.hopkinsmedicine.org/health/conditions-and-diseases/irondeficiency-anemia

  4. Gasche C, Lomer MCE, Cavill I, Weiss G. Iron, anaemia, and inflammatory bowel diseases. Gut. 2004;53(8):1190–1197. doi:10.1136/gut.2003.035758

  5. Weiss G, Goodnough LT. Anemia of chronic disease. N Engl J Med. 2005 Mar 10;352(10):1011-23. doi: 10.1056/NEJMra041809.

  6. Pasricha SR, Tye-Din J, Muckenthaler MU, Swinkels DW. Iron deficiency. Lancet. 2021;397(10270):233–248.

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