[3] When onset is slow, symptoms are often vague such as feeling tired, weak, short of breath, or having decreased ability to exercise.

[1] Iron-deficiency anemia is caused by blood loss, insufficient dietary intake, or poor absorption of iron from food.

[3] Sources of blood loss can include heavy periods, childbirth, uterine fibroids, stomach ulcers, colon cancer, and urinary tract bleeding.

[15] If symptoms present, patients may present with the sign of pallor (reduced oxyhemoglobin in skin or mucous membranes),[16] and the symptoms of feeling tired, weak, dizziness, lightheadedness, poor physical exertion, headaches, decreased ability to concentrate, cold hands and feet, cold sensitivity, increased thirst and confusion.

[25] 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.

[23] In women of childbearing age, heavy menstrual periods can be a source of blood loss causing iron-deficiency anemia.

[23][26] The World Health Organization estimates that approximately two billion people are infected with soil-transmitted helminths worldwide.

Some birth control methods, such as pills and IUDs, may decrease the amount of blood and therefore iron lost during a menstrual cycle.

Gastrointestinal bleeding can result from regular use of some medications, such as non-steroidal anti-inflammatory drugs (e.g. aspirin), as well as antiplatelets such as clopidogrel and anticoagulants such as warfarin; however, these are required in some patients, especially those with states causing a tendency to form blood clots.

[35] The National Academy of Medicine updated Estimated Average Requirements (EAR) and Recommended Dietary Allowances (RDA) in 2001.

[40] 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.

[46] Iron deficiency can lead to premature labor and to problems with neural functioning, including delays in language and motor development in the infant.

[44] Some studies show that women pregnant during their teenage years can be at greater risk of iron-deficiency anemia due to an already increased need for iron and other nutrients during adolescent growth spurts.

In addition, infants who are given cow's milk too early can develop anemia due to gastrointestinal blood loss.

[25] Children who are at risk for iron-deficiency anemia include:[47] Decreased levels of serum and urine hepcidin are early indicators of iron deficiency.

[41] Hepcidin binds to and induces the degradation of ferroportin, which is responsible for exporting iron from cells and mobilizing it to the bloodstream.

[41] Conditions such as high levels of erythropoesis, iron deficiency and tissue hypoxia inhibit hepcidin expression.

[41] Whereas systemic infection or inflammation (especially involving the cytokine IL-6) or increased circulating iron levels stimulate hepcidin expression.

[51][52] 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.

[55] A travel history to areas in which hookworms and whipworms are endemic may also help guide certain stool tests for parasites or their eggs.

[56] Although symptoms can play a role in identifying iron-deficiency anemia, they are often vague, which may limit their contribution to determining the diagnosis.

[18][62] It is unclear if screening pregnant women for iron-deficiency anemia during pregnancy improves outcomes in the United States.

[64] Even so, screening is a Level B recommendation suggested by the US Preventative Services Task Force in pregnant women without symptoms and in infants considered high risk.

[65] In severe acute cases, treatment measures are taken for immediate management in the interim, such as blood transfusions or intravenous iron.

[66][67][41] Intravenous iron can induce an allergic response that can be as serious as anaphylaxis, although different formulations have decreased the likelihood of this adverse effect.

When used as a treatment for IBD-related anemia, very low certainty evidence suggests a marked benefit with oral ferric maltol compared with placebo.

[70] 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.

It was unclear whether type of iron therapy administration affects the risk of death from any cause, including cardiovascular, nor whether it may alter the number of people who may require a blood transfusion or dialysis.

[71] Ferric derisomaltose (Monoferric) was approved in the United States in January 2020, for the treatment of iron deficiency anemia.

[78] A new study in 2024 suggests that nearly 1 in 3 Americans may have undiagnosed iron deficiency, which can cause fatigue, brain fog, and concentration problems.