Child development
Iron-deficiency anemia is associated with poor neurological development, including decreased learning ability and altered motor functions. This is because iron deficiency impacts the development of the cells of the brain called neurons. When the body is low on iron, the red blood cells get priority on iron, and it is shifted away from the neurons of the brain. Exact causation has not been established, but there is a possible long-term impact from these neurological issues. Increased iron demand often occurs during periods of growth, such as in children and pregnant women. For example, during stages of rapid growth, babies and adolescents may outpace their dietary intake of iron, which can result in deficiency in the absence of disease or a grossly abnormal diet. The World Health Organization estimates that approximately two billion people are infected with soil-transmitted helminths worldwide. Parasitic worms cause both inflammation and chronic blood loss by binding to a human's small-intestinal mucosa, and through their means of feeding and degradation, they can ultimately cause iron-deficiency anemia. The bleeding may occur quickly or slowly. Slow, chronic blood loss within the body – such as from a peptic ulcer, angiodysplasia, inflammatory bowel disease, a colon polyp or gastrointestinal cancer (e.g., colon cancer) – can cause iron-deficiency anemia.
Menstrual bleeding
Menstrual bleeding is a common cause of iron deficiency anemia in women of childbearing age.
Gastrointestinal bleeding
The most common cause of iron deficiency anemia in men and post-menopausal women is gastrointestinal bleeding. In addition, some bleeding disorders, such as von Willebrand disease and polycythemia vera, can cause gastrointestinal bleeding. When whole blood is donated, approximately 200 mg of iron is lost from the body.]]
The body normally gets the iron it requires from food. If a person consumes too little iron, or iron that is poorly absorbed (non-heme iron), they can become iron-deficient over time. Examples of iron-rich foods include meat, eggs, leafy green vegetables and iron-fortified foods. For proper growth and development, infants and children need dietary iron. For children, a high intake of cow's milk is associated with an increased risk of iron-deficiency anemia.
The National Academy of Medicine updated Estimated Average Requirements (EAR) and Recommended Dietary Allowances (RDA) in 2001. The current EAR for iron for women ages 14–18 is 7.9 mg/day, 8.1 for ages 19–50, and 5.0 thereafter (post menopause). For men, the EAR is 6.0 mg/day for ages 19 and up. The RDA is 15.0 mg/day for women ages 15–18, 18.0 for 19–50, and 8.0 thereafter; for men, 8.0 mg/day for ages 19 and up. (Recommended Dietary Allowances are higher than Estimated Average Requirements so as to cover people with higher than average requirements.) The RDA for pregnancy is 27 mg/day, and during lactation, 9 mg/day. For children ages 1–3 years, it is 7 mg/day, 10 for ages 4–8, and 8 for ages 9–13. The European Food Safety Authority refers to the collective set of information as Dietary Reference Values, with Population Reference Intakes instead of RDAs, and Average Requirements instead of EARs. For women, the Population Reference Intake is 13 mg/day for ages 15–17 years, 16 mg/day for women ages 18 and up who are premenopausal, and 11 mg/day postmenopausal; for pregnancy and lactation, 16 mg/day. For men, the Population Reference Intake is 11 mg/day for ages 15 and older. For children ages 1 to 14, the Population Reference Intake increases from 7 to 11 mg/day. The Population Reference Intakes are higher than the US RDAs, with the exception of pregnancy.
Iron malabsorption
Iron from food is absorbed into the bloodstream in the small intestine, primarily in the duodenum. Iron malabsorption is a less common cause of iron-deficiency anemia, but many gastrointestinal disorders can reduce the body's ability to absorb iron. Different mechanisms may be present.
In celiac disease, abnormal structural changes in the duodenum can decrease iron absorption. Abnormalities or surgical removal of the stomach can also lead to malabsorption by altering the acidic environment needed for iron to be converted into its absorbable form.
Pregnant women
Without iron supplementation, iron-deficiency anemia occurs in many pregnant women because their iron stores need to serve their own increased blood volume and be a source of hemoglobin for the growing baby and placental development.
Iron deficiency affects maternal well-being by increasing the risk of infections and complications during pregnancy. Oral iron supplementation during the early stages of pregnancy, specifically the first trimester, is suggested to decrease the adverse effects of iron-deficiency anemia throughout pregnancy and to decrease the negative impact that iron deficiency has on fetal growth. Iron deficiency can lead to premature labor and to problems with neural functioning, including delays in language and motor development in the infant.
- Preterm infants
- Low birth weight infants
- Infants fed with cow's milk under 12 months of age
- Breastfed infants who have not received iron supplementation after age 6 months, or those receiving non-iron-fortified formulas
- Children between the ages of 1 and 5 years old who receive more than 24 ounces (700 mL) of cow milk per day
- Children with low socioeconomic status
- Children with special health care needs
- Children of Hispanic ethnicity Hepcidin concentrations are also connected to the complex relationship between malaria and iron deficiency.
Mechanism
Anemia can result from significant iron deficiency. Conditions such as high levels of erythropoesis, iron deficiency and tissue hypoxia inhibit hepcidin expression. However, with the availability of reliable blood tests that can be more readily collected for iron-deficiency anemia diagnosis, a bone marrow aspiration is usually not obtained. Once iron deficiency anemia is confirmed, gastrointestinal blood loss is presumed to be the cause until proven otherwise since it can be caused by an otherwise asymptomatic colon cancer. The initial evaluation must include esophagogastroduodenoscopy and colonoscopy to evaluate for cancer or bleeding of the gastrointestinal tract. A travel history to areas in which hookworms and whipworms are endemic may also help guide certain stool tests for parasites or their eggs. Although symptoms can play a role in identifying iron-deficiency anemia, they are often vague, which may limit their contribution to determining the diagnosis.
Blood tests
{| class=wikitable floatright
|+ Change in lab values in iron deficiency anemia
|-
! Change
! Parameter
|-
| ↓
| ferritin, hemoglobin, mean corpuscular volume, mean corpuscular hemoglobin
|-
| ↑
| total iron-binding capacity, transferrin, red blood cell distribution width
|}
Routine blood tests often discover anemia. A sufficiently low hemoglobin by definition makes the diagnosis of anemia, and a low hematocrit value is also characteristic of anemia. Further studies will be undertaken to determine the cause of anemia. If the anemia is due to iron deficiency, one of the first abnormal values to be noted on a complete blood count, as the body's iron stores begin to be depleted, will be a high red blood cell distribution width, reflecting an increased variability in the size of red blood cells. With more severe iron-deficiency anemia, the peripheral blood smear may show hypochromic, pencil-shaped cells and, occasionally, small numbers of nucleated red blood cells. The platelet count may be slightly above the high limit of normal in iron-deficiency anemia (termed a mild thrombocytosis), but severe cases can present with thrombocytopenia (low platelet count).
Iron-deficiency anemia is confirmed by tests that include serum ferritin, serum iron level, serum transferrin, and total iron binding capacity. A low serum ferritin is most commonly found. However, serum ferritin can be elevated by any chronic inflammation and thus is not consistently decreased in iron-deficiency anemia. The percentage of iron saturation (or transferrin saturation index or percent) can be measured by dividing the level of serum iron by total iron binding capacity and is a value that can help to confirm the diagnosis of iron-deficiency anemia; however, other conditions must also be considered, including other types of anemia. During haemoglobin synthesis, trace amounts of zinc will be incorporated into protoporphyrin in the place of iron which is lacking. Protoporphyrin can be separated from its zinc moiety and measured as free erythrocyte protoporphyrin, providing an indirect measurement of the zinc-protoporphyrin complex. The level of free erythrocyte protoporphyrin is expressed in either μg/dl of whole blood or μg/dl of red blood cells. An iron insufficiency in the bone marrow can be detected very early by a rise in free erythrocyte protoporphyrin.
Further testing may be necessary to differentiate iron-deficiency anemia from other disorders, such as thalassemia minor. It is very important not to treat people with thalassemia with an iron supplement, as this can lead to hemochromatosis. A hemoglobin electrophoresis provides useful evidence for distinguishing these two conditions, along with iron studies.
Screening
It is unclear if screening pregnant women for iron-deficiency anemia during pregnancy improves outcomes in the United States. The same holds for screening children who are 6 to 24 months old. Even so, screening is a Level B recommendation suggested by the US Preventive Services Task Force in pregnant women without symptoms and in infants considered high risk. Screening is done with either a hemoglobin or hematocrit lab test. In severe acute cases, treatment measures are taken for immediate management in the interim, such as blood transfusions or intravenous iron. Two options are intravenous iron injections and blood transfusion. For patients with severe anemia, such as from blood loss, or who have severe symptoms such as cardiovascular instability, a blood transfusion may be considered. The type of iron preparation may be an important determinant of clinical benefit. Moderate-certainty evidence suggests response to treatment may be higher when IV ferric carboxymaltose, rather than IV iron sucrose preparation is used, despite very-low certainty evidence of increased adverse effects, including bleeding, in those receiving ferric carboxymaltose treatment.
A Cochrane review of controlled trials comparing intravenous (IV) iron therapy with oral iron supplements in people with chronic kidney disease, found low-certainty evidence that people receiving IV-iron treatment were 1.71 times as likely to reach their target hemoglobin levels. Overall, hemoglobin was 0.71g/dl higher than those treated with oral iron supplements. Iron stores in the liver, estimated by serum ferritin, were also 224.84 μg/L higher in those receiving IV-iron.
Epidemiology
thumb|upright=1.3|Deaths due to iron-deficiency anaemia per million persons in 2012:
thumb|upright=1.3|[[Disability-adjusted life year for iron-deficiency anemia per 100,000 inhabitants in 2004:
]]
A moderate degree of iron-deficiency anemia affects approximately 610 million people worldwide or 8.8% of the population. It is slightly more common in females (9.9%) than males (7.8%). Mild iron deficiency anemia affects another 375 million.
The prevalence of iron deficiency as a cause of anemia varies among countries; in the groups in which anemia is most common, including young children and a subset of non-pregnant women, iron deficiency accounts for a fraction of anemia cases in these groups (25% and 37%, respectively). Iron deficiency is common in pregnant women.
Within the United States, iron-deficiency anemia affects about 2% of adult males, 10.5% of White women, and 20% of African-American and Mexican-American women. A study in 2024 suggests that nearly 1 in 3 Americans may have undiagnosed iron deficiency, which can cause fatigue, brain fog, and concentration problems. The analysis of data from over 8,000 U.S. adults found that 14% had low iron levels, known as absolute iron deficiency; 15% had normal iron levels but their bodies couldn't effectively use the mineral, a condition called functional iron deficiency.
A map provides a country-by-country listing of what nutrients are fortified into specified foods. Some of the Sub-Saharan countries shown in the deaths from iron-deficiency anemia map from 2012 are, as of 2018, fortifying foods with iron.