[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Red cells and bleeding disorders](https://durgical.com/en/general-pathology/areas/red-cells/) › Iron deficiency anaemia

# Iron deficiency anaemia

- Lesion

The commonest anaemia in the world: iron stores empty first, then cells become small and pale. Chronic bleeding is the usual cause in adults.

Updated Nov 12, 2026

## Key points

- Stages: storage iron depleted (low ferritin) → low serum iron and transferrin saturation → anaemia.
- Labs: low ferritin, low serum iron, high total iron-binding capacity, transferrin saturation under about 15%, low hepcidin.
- In an adult man or a postmenopausal woman, iron deficiency means GI bleeding until proven otherwise (colon cancer, ulcer).
- Smear: microcytic hypochromic cells with a thin rim of haemoglobin, pencil cells; reactive thrombocytosis is common.
- Pica, koilonychia, atrophic glossitis; Plummer–Vinson syndrome adds oesophageal webs.

## What it is

Iron deficiency is the most common nutritional disorder worldwide. Iron is absorbed in the duodenum (DMT1 at the apical membrane, ferroportin at the basolateral), carried by transferrin and stored as ferritin and haemosiderin; hepcidin from the liver limits absorption and macrophage release. Deficiency results from poor intake (infants, vegans), poor absorption (coeliac disease, gastrectomy), increased needs (growth, pregnancy) or, most often in adults, chronic blood loss. Stores empty first, then transport iron falls, and finally microcytic hypochromic anaemia appears.

## Structure

- Marrow: mild erythroid hyperplasia with small, ragged normoblasts; no stainable iron in macrophages (Prussian blue).
- Blood: microcytosis, hypochromia, anisocytosis (high RDW), elongated pencil cells.

## Step by step

- Iron loss or poor intake exceeds absorption.
- Ferritin stores in macrophages and liver are used up first.
- Hepcidin falls, maximizing absorption, but supply is still insufficient.
- Serum iron and transferrin saturation fall; erythroid precursors cannot fill with haemoglobin.
- Extra divisions produce small, pale red cells; iron-containing enzymes elsewhere also suffer.

## Telling the microcytic anaemias apart

| Disorder | Ferritin | Serum iron / TIBC | Other clue |
| --- | --- | --- | --- |
| [Iron deficiency](https://durgical.com/en/conditions/iron-deficiency-anaemia/) | Low | Low iron, high TIBC | High RDW, pencil cells, absent marrow iron |
| [Thalassaemia trait](https://durgical.com/en/conditions/thalassemias/) | Normal | Normal | Red cell count normal or high, target cells, HbA2 high in β trait |
| [Anaemia of inflammation](https://durgical.com/en/conditions/anaemia-of-chronic-disease/) | Normal or high | Low iron, low TIBC | Iron trapped in marrow macrophages, hepcidin high |
| [Sideroblastic anaemia](https://durgical.com/en/conditions/sideroblastic-anaemia/) | High | High iron | Ring sideroblasts in the marrow |

## Clinical notes

- In Colombia and Latin America iron deficiency is the main cause of anaemia in children and pregnant women; hookworm adds blood loss in rural tropical areas.
- Response to iron therapy starts with a reticulocyte rise.

## Memory aid

Ferritin falls first, TIBC climbs, cells shrink and fade; in an adult, find the bleed.

## Test yourself

Think of the answer, then tap the question to see it.

## Which laboratory value falls first in developing iron deficiency?

Serum ferritin, reflecting depleted storage iron.

## How do you tell iron deficiency from anaemia of inflammation using TIBC?

TIBC is high in iron deficiency and low or normal in anaemia of inflammation.

## Which syndrome combines iron deficiency, atrophic glossitis and oesophageal webs?

Plummer–Vinson syndrome.

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## Elsewhere in DurgiPedia

- [Iron metabolism](https://durgical.com/en/biochemistry/topics/iron-metabolism/)
- [Body iron balance](https://durgical.com/en/physiology/body-iron-balance/)
- [Absorption of iron, calcium and vitamin B12](https://durgical.com/en/physiology/absorption-of-iron-calcium-and-vitamin-b12/)

## Connections

## Related 5

- [Anaemia of chronic inflammation: IL-6, hepcidin and locked-away iron](https://durgical.com/en/general-pathology/anaemia-of-chronic-inflammation-il-6-hepcidin-and-locked-away-iron/)
- [Thalassaemias: β and α](https://durgical.com/en/general-pathology/thalassaemias-and/)
- [Oesophageal obstruction: stenosis, webs, rings, diverticula](https://durgical.com/en/general-pathology/oesophageal-obstruction-stenosis-webs-rings-diverticula/)
- [Intestinal helminths](https://durgical.com/en/general-pathology/intestinal-helminths/)
- [Peptic ulcer](https://durgical.com/en/general-pathology/peptic-ulcer/)

## Related conditions 9

- [Iron deficiency anaemia](https://durgical.com/en/conditions/iron-deficiency-anaemia/)
- [Upper gastrointestinal bleeding](https://durgical.com/en/conditions/upper-gastrointestinal-bleeding/)
- [Lower gastrointestinal bleeding](https://durgical.com/en/conditions/lower-gastrointestinal-bleeding/)
- [Thalassemias (α and β)](https://durgical.com/en/conditions/thalassemias/)
- [Sideroblastic anaemia](https://durgical.com/en/conditions/sideroblastic-anaemia/)
- [Anaemia of chronic disease (anaemia of inflammation)](https://durgical.com/en/conditions/anaemia-of-chronic-disease/)
- [Coeliac disease](https://durgical.com/en/conditions/coeliac-disease/)
- [Abnormal uterine bleeding](https://durgical.com/en/conditions/abnormal-uterine-bleeding/)
- [Lead poisoning](https://durgical.com/en/conditions/lead-poisoning/)

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Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [Iron deficiency anemia: MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/000584.htm) (MedlinePlus, US National Library of Medicine, 2026); [Prevalence of Anemia in Children from Latin America and the Caribbean and Effectiveness of Nutritional Interventions: Systematic Review and Meta⁻Analysis](https://europepmc.org/article/PMC/PMC6356363) (Nutrients, 2019).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/iron-deficiency-anaemia/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/iron-deficiency-anaemia/