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Health condition · Clinically reviewed

Iron deficiency anaemia, finding the cause and putting the iron back.

The commonest anaemia in the world - and the one where tests, endoscopy and the right iron plan turn tired into well.

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Why trust this guide

  • 01

    Clinically reviewed

    Written by our editorial team and reviewed by a registered UK clinician before publication.

  • 02

    Sourced from guidance

    Checked against NICE NG8, BSG, BSH and WHO guidance you can see at the end.

  • 03

    Current for 2026

    Reflects modern UK practice including alternate-day oral iron and newer IV iron formulations.

Key facts

Iron deficiency anaemia at a glance.

The essentials in plain English - what it is, what causes it, and how it is investigated and treated in the UK.

  • What it is

    The most common anaemia worldwide - a shortage of iron limits red-cell production, giving a microcytic hypochromic picture on the blood film.

  • Main drivers

    Blood loss (usually gastrointestinal or menstrual in adults), poor dietary intake, malabsorption and periods of increased demand.

  • Key test

    Ferritin below 30 micrograms per litre confirms iron deficiency in most adults, alongside a full blood count and film.

  • Adults over 50

    Men and postmenopausal women without a clear cause need upper and lower GI endoscopy per BSG guidance.

  • Foundation therapy

    Oral iron - ferrous sulphate 200mg daily or alternate-day dosing, which is better tolerated and often absorbed as well.

  • IV iron

    For intolerance, malabsorption, chronic disease or a rapid response - ferric carboxymaltose and ferric derisomaltose are the modern options.

Why this guide matters

Iron replacement is only half the answer.

The three points below shape everything else on this page - find the source of iron loss, replace stores fully, and follow up until ferritin is stable.

  • Find the source of the loss

    GI blood loss is the leading cause in men and postmenopausal women. Endoscopy pathways matter as much as the tablet.

  • Replace stores, not just Hb

    Ferritin lags behind haemoglobin. Stopping iron the moment blood counts normalise sets up relapse in months.

  • Escalate to IV when it fits

    Intolerance, malabsorption, IBD, heart failure, chronic kidney disease and pre-surgery scenarios all favour a modern IV iron infusion.

How the diagnosis is made

From first blood test to a clear plan.

The steps a UK GP, gastroenterologist or haematologist will normally follow - so you know what to expect and why.

  1. 01

    Assessing

    History and red flags

    Diet, menstrual pattern, GI symptoms and any weight loss, rectal bleeding or dyspepsia that flags a cancer pathway.

  2. 02

    Assessing

    Full blood count and film

    Microcytic hypochromic anaemia with pencil cells and anisopoikilocytosis on the film is the classic pattern.

  3. 03

    Assessing

    Ferritin and CRP

    Ferritin under 30 confirms deficiency. CRP helps interpret a normal or raised ferritin against inflammation.

  4. 04

    Confirming

    Transferrin and CHr if needed

    Transferrin saturation under 20 percent, soluble transferrin receptor and reticulocyte haemoglobin help in complex cases.

  5. 05

    Confirming

    Coeliac screen

    Tissue transglutaminase antibodies with total IgA - coeliac disease is a common and treatable cause.

  6. 06

    Sourcing

    GI endoscopy pathway

    Upper GI gastroscopy and colonoscopy in men and postmenopausal women, and any adult over 50 without a clear alternative cause.

  7. 07

    Sourcing

    Menstrual and gynaecology review

    For premenopausal women with heavy periods - RCOG-led assessment before assuming a gynaecological cause is enough.

Typical timeline: from a first ferritin to a settled treatment plan in a few weeks.

Causes

Where the iron is going.

Iron deficiency is a symptom, not a diagnosis. The four buckets below cover almost every adult case.

  • Blood loss

    The main cause in adults - occult GI bleeding from colon cancer, peptic ulcers or angiodysplasia, plus heavy periods and recurrent nosebleeds.

  • Malabsorption

    Coeliac disease, inflammatory bowel disease, H. pylori gastritis, autoimmune atrophic gastritis and post-bariatric surgery anatomy all reduce iron uptake.

  • Reduced intake

    Low dietary iron - particularly in restrictive vegetarian and vegan diets without careful planning, older adults with poor appetite and low-variety diets in childhood.

  • Increased demand

    Pregnancy, infancy and adolescence all raise iron needs. Endurance athletes lose iron through footstrike haemolysis and sweat and often need active supplementation.

Symptoms

What iron deficiency actually feels like.

Fatigue and breathlessness dominate. The specific mucosal, nail and craving features often point straight to iron.

  • Fatigue and breathlessness

    The commonest complaint - tiredness on effort, breathlessness climbing stairs and a general loss of stamina.

  • Palpitations and pallor

    A racing heart on mild exertion and pale skin, palms and conjunctivae as haemoglobin falls.

  • Angular cheilitis and glossitis

    Cracked corners of the mouth and a sore, smooth tongue - classic mucosal signs of long-standing deficiency.

  • Koilonychia and brittle nails

    Spoon-shaped nails and easy splitting - a late sign in chronic iron deficiency.

  • Hair loss

    Diffuse shedding of hair, often noticed months into low iron stores and slow to reverse after treatment.

  • Pica and pagophagia

    Cravings for non-food substances or, classically, ice - a specific pointer to iron deficiency.

  • Restless legs

    An urge to move the legs at rest, worse in the evenings - often improves once iron stores are restored.

  • Red flag - GI bleeding

    Rectal bleeding, black stools, unexplained weight loss or dyspepsia - a cancer pathway referral, not a supplement.

Treatment

How iron deficiency anaemia is treated in the UK.

Oral iron first, IV iron for intolerance or urgency, and a clear plan for the underlying cause. Transfusion is reserved for the severest end.

  • Oral ferrous sulphate

    Ferrous sulphate 200mg once daily, or 100 to 200mg on alternate days - modern evidence favours alternate-day dosing for tolerance and absorption.

  • Vitamin C and diet

    Take iron with vitamin C, avoid tea and coffee at the same time, and build in haem-iron sources where diet allows.

  • Treat the underlying cause

    A cancer, coeliac diagnosis or heavy menstrual bleed matters more than the tablet - specialist input is often needed.

  • H. pylori eradication

    If H. pylori is positive, eradication improves iron absorption and often the anaemia with it.

  • IV ferric carboxymaltose

    A single-visit option via a ferric carboxymaltose clinic - useful for intolerance, malabsorption or a rapid target.

  • IV ferric derisomaltose

    Another modern high-dose IV iron given through an IV iron therapy service, often in a single infusion.

  • IV iron for heart failure

    The IV iron heart failure clinic supports patients where iron deficiency worsens symptoms even without frank anaemia.

  • Transfusion in severe cases

    Reserved for severe symptomatic anaemia or bleeding - a bridge, not a substitute for iron replacement and treating the cause.

What this guide is based on

The sources behind every claim on this page.

UK national guidance and specialist society standards, current at the time of last review.

Key references

Guidelines and standards we relied on.

A quiet reminder

This guide is for information, not medical advice.

Your GP, gastroenterologist or haematologist knows your history and can tell you which parts apply to you. If in doubt, get seen.

  • NICE. Iron deficiency anaemia: assessment and management (NG8 and NICE CKS).

  • British Society of Gastroenterology. Guidelines for the management of iron deficiency anaemia in adults.

  • British Society for Haematology. UK guidelines on the diagnosis and management of iron deficiency.

  • World Health Organization. Nutritional anaemias - tools for effective prevention and control.

Red flags

When iron deficiency needs urgent attention.

Most iron deficiency is manageable in primary care - but these features change the pathway from GP to specialist.

  • Rectal bleeding or melaena

    Visible blood or black tarry stools with iron deficiency needs a two-week wait referral, not a supplement trial.

  • Unexplained weight loss

    Iron deficiency plus weight loss raises the risk of GI malignancy - urgent investigation of the bowel is mandatory.

  • New dyspepsia over 55

    Persistent upper GI symptoms in an older adult with iron deficiency needs urgent upper GI endoscopy.

  • Postmenopausal bleeding

    Any bleeding after the menopause with anaemia needs urgent gynaecology assessment alongside GI investigation.

  • Severe symptomatic anaemia

    Chest pain, severe breathlessness or collapse with a low haemoglobin needs same-day assessment and possible transfusion.

  • Pregnancy with iron deficiency

    Anaemia in pregnancy increases risk to mother and baby - obstetric-led replacement, sometimes IV, is standard.

  • Failure to respond to oral iron

    No rise in haemoglobin after 4 to 6 weeks of a tolerated oral dose suggests malabsorption, ongoing loss or a wrong diagnosis.

  • Recurrent iron deficiency

    Repeated episodes need a firm cause - inflammatory bowel disease, angiodysplasia or HHT are all worth considering.

  • Recurrent epistaxis

    Frequent nosebleeds can drain iron stores - see epistaxis and nosebleeds for the ENT pathway.

Living with it

A treatable condition, with a clear plan.

Four things make the biggest difference day to day - the timing of your tablets, what you take them with, patience with recovery, and finishing the diagnostic job.

A quiet reminder

Consistency beats intensity, every time.

A steady dose over months does more than a heroic week that ends in nausea and abandoned tablets.

  1. 01 Timing

    Alternate-day iron works

    A single dose every other day is often absorbed as well as daily dosing, with fewer side effects. It is now a mainstream option.

  2. 02 With

    Take with vitamin C, not tea

    A glass of orange juice helps absorption. Tea, coffee and calcium blunt it, so keep them a couple of hours away from your iron.

  3. 03 Patience

    Give it 4 to 6 weeks

    Haemoglobin rises steadily and ferritin lags behind. Rechecking too early can mislead - stick with a plan for at least a month.

  4. 04 Follow-up

    Find and fix the cause

    Replacing iron without finding the cause is only half the job. Endoscopy, coeliac screening and gynaecology input matter as much as the tablet.

Frequently asked

Everything we get asked about iron deficiency.

Quick answers on ferritin thresholds, endoscopy, oral iron dosing and IV iron infusions.

  • What is iron deficiency anaemia?

    The most common anaemia worldwide - a shortage of iron limits red-cell production and gives a microcytic, hypochromic picture. In adults it usually reflects blood loss, malabsorption, low intake or increased demand rather than a simple dietary problem.

  • How is iron deficiency diagnosed in the UK?

    A full blood count and film, ferritin and CRP are the core tests. Ferritin under 30 micrograms per litre confirms deficiency in most people. Transferrin saturation, soluble transferrin receptor and reticulocyte haemoglobin help in complex or inflammatory settings.

  • Why do I need an endoscopy?

    BSG guidance recommends upper and lower GI endoscopy in men, postmenopausal women and any adult over 50 with unexplained iron deficiency, because occult GI bleeding - including bowel and stomach cancer - is a leading cause. Finding a source matters as much as replacing the iron.

  • What is the best way to take oral iron?

    Ferrous sulphate 200mg once daily, or 100 to 200mg on alternate days. Alternate-day dosing is often better tolerated and absorbs as well or better. Take it with vitamin C, away from tea, coffee, calcium and thyroid medication.

  • When is IV iron used instead of tablets?

    When oral iron is not tolerated, not absorbed or not fast enough - for example in inflammatory bowel disease, after bariatric surgery, in chronic kidney disease or heart failure, or when a rapid rise in haemoglobin is needed before surgery or pregnancy. Ferric carboxymaltose and ferric derisomaltose are the usual choices.

  • How long does it take to feel better?

    Most people notice more energy in 2 to 4 weeks. Haemoglobin normalises in 2 to 3 months, but ferritin - the iron store - can take 3 to 6 months longer to refill. Stopping iron too early is the most common reason for relapse.

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