Iron Deficiency Anaemia
What iron deficiency anaemia is, which blood tests identify it, and why the cause always needs finding.
Last revised
Too little iron to make enough haemoglobin, so blood carries less oxygen. It causes fatigue, breathlessness and poor concentration, and it is a finding rather than a diagnosis: the reason for the deficiency always needs establishing.
The two tests
A full blood count shows haemoglobin and red cell size; in iron deficiency the cells are typically small and pale. Ferritin measures stored iron and falls before haemoglobin does, so it identifies deficiency earlier. Ferritin rises with inflammation, so a normal value in someone with an inflammatory condition does not reliably exclude deficiency, and other tests may be needed.
Why the cause matters more than the number
Iron deficiency has a reason. In women of reproductive age, menstrual loss is much the most common. Otherwise the priority is excluding gastrointestinal blood loss, which can be the first sign of a bowel cancer. Coeliac disease impairs absorption and is routinely tested for. In men, and in women past menopause, unexplained iron deficiency anaemia is a recognised indication for urgent investigation of the gut.
Treatment
Oral iron, typically ferrous sulfate, ferrous fumarate or ferrous gluconate. Absorption improves taken on an empty stomach with a source of vitamin C, and is reduced by tea, coffee, calcium and some medicines. Side effects — constipation, dark stools, nausea — are common; taking it on alternate days is often as effective and better tolerated. Treatment continues for around three months after haemoglobin normalises, to refill stores.
Diet alone is rarely enough
Once anaemia is established, diet cannot usually correct it at a useful rate, which is why supplements are prescribed. Diet matters for prevention and maintenance: haem iron from meat and fish is far better absorbed than non-haem iron from pulses, fortified cereals, tofu and greens, which benefit from vitamin C taken alongside.
At a glance
| Term | Detail |
|---|---|
| Test for stored iron | serum ferritin |
| Test for anaemia | full blood count, haemoglobin |
| Typical red cell picture | small (low MCV) and pale (low MCH) |
| Most common cause, women of reproductive age | menstrual blood loss |
| Always excluded in men and postmenopausal women | gastrointestinal blood loss |
| Routinely tested alongside | coeliac disease |
| Treatment duration | about 3 months beyond normal haemoglobin, to refill stores |
| Improves absorption | vitamin C; alternate-day dosing often better tolerated |
When to get help
See a GP for unexplained fatigue with breathlessness or palpitations. Iron deficiency in a man, or in a woman who has been through menopause, requires investigation of the gut and should never simply be supplemented. Seek urgent advice for black tarry stools, visible blood in stool, vomiting blood, chest pain, or breathlessness at rest.
Where to go next
Where this comes from
- NICE - Anaemia, iron deficiency clinical knowledge summary
- NHS - Iron deficiency anaemia
- British Society of Gastroenterology - iron deficiency anaemia guidelines
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
