Haematology & Oncology

Iron-Deficiency Anaemia

Iron-deficiency anaemia reflects depleted iron available for haemoglobin production; replace the iron, but always investigate the pattern of loss, demand or malabsorption that caused it.

In a nutshell

Confirm iron depletion, replace iron and find the cause. In adults without an obvious explanation, particularly men and postmenopausal women, use the current NICE colorectal FIT pathway and appropriate GI investigation rather than treating the haemoglobin result in isolation.

Classic presentation

Fatigue, reduced exercise tolerance and pallor with low haemoglobin, low MCV/MCH and depleted iron stores, with the source often being menstrual loss, gastrointestinal blood loss or malabsorption.

Key points

Ferritin is the most useful iron-store marker but can be falsely normal with inflammation; use transferrin saturation and context.
Microcytosis is not synonymous with iron deficiency: thalassaemia, inflammation and other disorders can mimic it.
The initial cause framework is loss, demand or reduced absorption; ask about menstrual, gastrointestinal, urinary, dietary, pregnancy and surgical factors.
Current NICE NG12 recommends offering quantitative FIT to adults with iron-deficiency anaemia; a result at or above the current NICE cut-off meets the suspected colorectal-cancer referral threshold.
A low or missing FIT does not overrule strong concern, persistent symptoms, an abdominal mass or unexplained ongoing anaemia.
BSG generally recommends gastroscopy and colonoscopy as first-line GI investigations in men and postmenopausal women with newly diagnosed iron-deficiency anaemia; CT colonography is an alternative when colonoscopy is unsuitable.
Screen for coeliac disease while the patient is eating gluten; request total IgA and IgA tissue-transglutaminase first.
Start oral iron promptly, monitor the haemoglobin response within 2 to 4 weeks and continue for around 3 months after haemoglobin normalises.
Use IV iron when oral treatment is contraindicated, ineffective, not tolerated, unlikely to work or correction is urgent.
Transfusion is selective and does not replace iron; use the current NICE threshold and target pathway with clinical reassessment.

First-line investigation

FBC and iron studies with ferritin and transferrin saturation, plus urinalysis and coeliac serology, followed by the current NICE FIT and specialist GI investigation pathway when indicated.

Management

Recognise severe anaemia and stabilise

Chest pain, syncope, breathlessness at rest, heart failure, haemodynamic instability or ongoing bleeding requires urgent assessment and source control, not routine oral iron alone.^6,1
If red-cell transfusion is required, use a restrictive, single-unit and reassessment approach when appropriate; restore iron afterwards because transfusion does not replete stores.^6,1

Confirm deficiency and start replacement

Confirm iron deficiency with ferritin and transferrin saturation, interpret ferritin alongside inflammation, and begin oral iron without usually waiting for the complete investigation pathway.¹
Request urinalysis, coeliac serology while the patient is eating gluten, and a directed history for menstrual, GI, urinary, dietary, medication, pregnancy and surgical causes.^1,2,3

Find gastrointestinal and other sources

Offer quantitative FIT to adults with iron-deficiency anaemia under current NICE NG12; refer on the suspected colorectal-cancer pathway when FIT reaches the current NICE cut-off, while safety-netting low or missing results.⁴
Use BSG’s specialist pathway of gastroscopy and colonoscopy generally first-line in men and postmenopausal women; use CT colonography when colonoscopy is unsuitable and investigate younger menstruating women when additional concern exists.^1,4

Escalate treatment failure or urgent correction

Consider IV iron when oral iron is contraindicated, ineffective, not tolerated, unlikely to work because of malabsorption or ongoing loss, or correction is particularly urgent.^1,5
If bidirectional endoscopy is negative but the haemoglobin response is inadequate or the anaemia recurs, investigate the small bowel and renal tract with specialist input; consider capsule endoscopy first for mucosal small-bowel disease.¹

Confirm recovery and prevent recurrence

Check response within 2 to 4 weeks, continue oral iron for around 3 months after haemoglobin normalises and monitor the blood count periodically for recurrence.¹
Act on every investigation result and safety-net for recurrent symptoms, overt GI bleeding, progressive weight loss, dysphagia, chest pain, syncope or breathlessness.^1,4

Exam traps

Do not label every microcytic anaemia as iron deficiency without iron studies; thalassaemia trait can have marked microcytosis with preserved iron.
Do not let a normal ferritin exclude iron deficiency in inflammatory disease.
Do not start a gluten-free diet before coeliac testing and specialist confirmation.
Do not let a low or missing FIT overrule strong clinical concern or ongoing unexplained symptoms.
Do not delay iron replacement while waiting for most investigations, unless colonoscopy is imminent.
A haemoglobin response supports iron deficiency, but failure to respond needs investigation rather than automatic escalation to indefinite oral iron.
Transfusion treats oxygen-carrying capacity temporarily, not the iron deficit; continue iron replacement after transfusion.
In men and postmenopausal women, an apparently asymptomatic presentation can still conceal gastrointestinal pathology.

Illustrations

Blood film in iron-deficiency anaemiaPeripheral blood film showing microcytic, hypochromic red cells with anisopoikilocytosis and pencil cells; correlate with iron studies because microcytosis is not specific.E. Uthman, MD, Wikimedia Commons · CC-BY-SA-2.0

KoilonychiaPhotograph of spoon-shaped, brittle fingernails associated with chronic iron deficiency; clinical signs are supportive rather than diagnostic.CHeitz, Wikimedia Commons · CC-BY-2.0

Mechanisms of iron deficiencyDiagram mapping chronic blood loss, increased demand, poor intake and impaired absorption to the clinical causes of iron-deficiency anaemia.PassFinals · original

Key sources

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.