Medical Encyclopaedia › Iron deficiency (short definition)
In brief: Iron deficiency is the most common nutrient deficiency worldwide. The body needs iron above all to form the red blood pigment haemoglobin; if it is lacking over a longer period, iron deficiency anaemia develops.
Causes
The most common cause is blood loss, for example through heavy menstruation or unnoticed bleeding in the gastrointestinal tract. Increased requirements during pregnancy, breastfeeding and growth, a low-iron diet and impaired absorption, for example in coeliac disease, chronic inflammatory bowel disease or long-term use of acid blockers, are further causes.
Symptoms
Typical symptoms are tiredness, reduced performance, pallor, headache, shortness of breath on exertion, brittle nails, hair loss and cracked corners of the mouth. Some of those affected feel a craving for ice or unusual substances (pica) or have restless legs.
Diagnosis
The most important laboratory value is ferritin, which reflects the iron stores. As it can be raised in inflammation, transferrin saturation, CRP and a blood count are often measured in addition. In adults, the cause should always be investigated – in men and in women after the menopause in particular, a gastroscopy and colonoscopy are often recommended.
Treatment
The cause is treated and iron is supplemented, usually as tablets or syrup. Newer data suggest that taking it every other day is similarly effective and often better tolerated. Common side effects are stomach complaints and constipation; the stool turns dark. In the case of intolerance, absorption disorders or severe deficiency, iron can be given as an infusion. Iron preparations should not be taken without a proven deficiency, as an excess can be harmful.
Related terms in the encyclopaedia
Anaemia, Ferritin, Haemoglobin, Transferrin saturation, Blood count, Coeliac disease, Haemochromatosis, Tiredness
Sources
- Deutsche Gesellschaft für Hämatologie und Medizinische Onkologie (DGHO): Onkopedia-Leitlinie Eisenmangel und Eisenmangelanämie
- IQWiG: gesundheitsinformation.de – Gesundheitsinformationen des Instituts für Qualität und Wirtschaftlichkeit im Gesundheitswesen
Note: This article is for general information and does not replace advice, diagnosis or treatment from a doctor or pharmacist. Last updated: October 2026.