🩸  New patient guide: Iron Deficiency Anaemia — read it now  ·  New guides added regularly

Blood🩸Doctor
open
close
Uncategorised

Iron Deficiency Anaemia: Causes, Symptoms and Treatment

August 7, 2026 | by Dr Abdul Mannan FRCPath FCPS

Blood🩸Doctor · Patient guide

Iron deficiency anaemia:
causes, symptoms and treatment

Iron deficiency is the single most common cause of anaemia. This guide walks through why iron runs low, what it can feel like, and how clinicians decide between diet, tablets and iron infusions.

Ferritin firstThe usual starting point for iron stores.
Find the causeDiet, blood loss or absorption.
Then replace itDiet, tablets or infusion.

Iron deficiency anaemia means the body does not have enough iron to make healthy red blood cells. It is common and usually treatable, but replacing the iron is only half the job — the other half is working out why the level fell in the first place.

Iron is used by the bone marrow to build haemoglobin, the protein in red blood cells that carries oxygen. When iron stores run low, the marrow cannot keep up, red cells become smaller and paler than normal, and the blood carries less oxygen than it should.
“A ferritin result is a clue, not a diagnosis — the cause still needs finding.”

What it can feel like

Many people have no symptoms at all, especially when the deficiency develops slowly. Others notice tiredness, reduced exercise tolerance, breathlessness on exertion, palpitations, headaches, brittle nails, hair thinning, a sore or smooth tongue, or a craving to eat non-food items such as ice (a recognised feature called pica).

Do not wait for a routine appointment if there is new chest pain, collapse or fainting, black or bloody stools, vomiting blood, heavy ongoing bleeding, or rapid deterioration. In the UK, use urgent services such as 999/A&E when appropriate.

Why iron runs low

Iron deficiency has a cause. Finding it matters as much as replacing the iron, because treating the number without treating the reason means the deficiency often returns.

CategoryTypical examplesWhy it matters
Blood lossHeavy periods, gastrointestinal bleeding (including from ulcers, polyps or bowel cancer), regular blood donation.The most common cause in adults; gastrointestinal bleeding can be silent, so it needs actively excluding, not assuming.
Reduced absorptionCoeliac disease, previous gastric or bowel surgery, medicines that reduce stomach acid, Helicobacter pylori infection.Diet alone will not correct the deficiency if the gut cannot absorb the iron given.
Reduced intakeDiets low in iron-rich foods, restrictive eating patterns.Less common as a sole cause in adults than blood loss, but relevant, especially alongside other risk factors.
Increased demandPregnancy, rapid growth in childhood and adolescence.The body needs more iron than usual; a level that would be normal outside pregnancy may not be enough during it.
Important: in adults, especially those over 50 or with a change in bowel habit, new iron deficiency should prompt a search for gastrointestinal blood loss. This is a common and appropriate reason for referral, not an alarming one — most causes found are treatable.

Tests and the treatment approach

Ferritin and iron studies confirm depleted stores, though ferritin can rise with inflammation and needs interpreting in context. A full blood count and cell indices confirm the anaemia pattern; further tests (such as coeliac screening or gastrointestinal investigation) are chosen based on the clinical picture, not ordered as a blanket panel.

Diet

Iron-rich foods (red meat, oily fish, eggs, dark green leafy vegetables, pulses, fortified cereals) help maintain iron stores and support recovery, but diet alone rarely corrects an established deficiency quickly.

supports recoveryrarely enough alone

Oral iron

Iron tablets are usually the first-line treatment once a cause is being investigated. Side effects such as constipation, nausea or dark stools are common and dose or timing can often be adjusted. Response is checked with a repeat blood count after some weeks, not assumed.

first-line for most peopleresponse is checked, not assumed

Intravenous iron

IV iron infusion is considered when oral iron is not tolerated, not absorbed (for example in coeliac disease or after certain gut surgery), the deficiency is severe, or correction is needed quickly (for example in later pregnancy or before surgery). It is given in a monitored healthcare setting.

for intolerance, malabsorption or urgencymonitored setting

Questions to bring to an appointment

  • Has a likely cause been identified, or is it still being investigated?
  • Is there anything to suggest gastrointestinal blood loss that needs further assessment?
  • Would tablets, a change in diet, or an iron infusion suit my situation best?
  • When should the blood count be rechecked to confirm the treatment is working?
  • Are there any medicines or conditions I have that could affect iron absorption?
“Replace the iron, but don’t stop at the number — ask why it was low.”

A final word

Iron deficiency anaemia is common and, once the cause is found, usually straightforward to treat. The combination of a full blood count, ferritin and iron studies, and a clear look for the underlying cause is what turns a low number into a proper diagnosis.

Educational note: This article is for general education and cannot diagnose an individual. Laboratory ranges, test choices and treatment decisions vary between adults, children, pregnancy and clinical settings. Discuss your own results with an appropriate clinician and follow local guidance.

Reliable further reading

Reviewed: August 2026  |  Audience: adults, families and learners