Iron is present in all cells in the human body and has several vital functions, such as carrying oxygen to the tissues from the lungs as a key component of the hemoglobin protein, acting as a transport medium for electrons within the cells in the form of cytochromes, and facilitating oxygen enzyme reactions in various tissues.

A primary cause of iron deficiency in non-pregnant women is menstrual bleeding, which accounts for their comparatively higher risk than men.

[3] If not treated can cause problems like an irregular heartbeat, pregnancy complications, and delayed growth in infants and children that could affect their cognitive development and their behavior.

Haematuria in athletes is most likely to occur in those that undergo repetitive impacts on the body, particularly affecting the feet (such as running on a hard road, or Kendo) and hands (e.g. Conga or Candombe drumming).

[18] Consumption data were updated in a 2014 U.S. government survey and reported that for men and women ages 20 and older the average iron intakes were, respectively, 16.6 and 12.6 mg/day.

[20] Iron is needed for bacterial growth making its bioavailability an important factor in controlling infection.

[22] Lactoferrin is also concentrated in tears, saliva, and wounds to bind iron to limit bacterial growth.

The underlying inflammation can be caused by fever,[24] inflammatory bowel disease, infections, chronic heart failure (CHF), carcinomas, or following surgery.

A moderate iron deficiency, in contrast, can protect against acute infection, especially against organisms that reside within hepatocytes and macrophages, such as malaria and tuberculosis.

[citation needed] Before commencing treatment, there should be a definitive diagnosis of the underlying cause of iron deficiency.

In adults, 60% of patients with iron-deficiency anemia may have underlying gastrointestinal disorders leading to chronic blood loss.

The choice of the supplement will depend upon both the severity of the condition, the required speed of improvement (e.g. if awaiting elective surgery), and the likelihood of treatment being effective (e.g. if the patient has underlying IBD, is undergoing dialysis, or is having ESA therapy).

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.

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

[28] 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 the 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.

[33] For example, oxalates and phytic acid form insoluble complexes which bind iron in the gut before it can be absorbed.

[34] Legumes and dark-green leafy vegetables like broccoli, kale and Asian greens are especially good sources of iron for vegetarians and vegans.

[43] Current evidence is limited to base any recommendations that intravenous iron therapy is beneficial for treating non-anemic, iron-deficient adults.

The presence of Helicobacter pylori in the stomach can cause inflammation and can lower the threshold for the development of gastric cancer.

In the setting of iron deficiency, H. pylori causes more severe inflammation and the development of premalignant lesions.