GPAtlas🧭 When to suspect
Suspect iron deficiency anaemia (IDA) – the commonest cause of a microcytic, hypochromic anaemia – in anyone presenting with:
• Fatigue
• Reduced exercise tolerance
• Exertional breathlessness
It is defined by a low haemoglobin together with a low serum ferritin, with red cells that are typically microcytic (low mean cell volume, MCV) and hypochromic.
Raise suspicion where there is a plausible mechanism:
• Dietary insufficiency
• A source of blood loss (menorrhagia or gastrointestinal (GI) loss)
• Malabsorption
• Increased physiological demand such as pregnancy
Classic clinical signs – pallor, koilonychia, angular stomatitis – support the diagnosis but their absence does not exclude it.
The key caveat in primary care is that chronic, slow blood loss is often well tolerated: symptoms and signs may be entirely absent even at a very low haemoglobin, so the diagnosis is frequently made on bloods alone.
Confirm and treat the iron deficiency, and identify the underlying cause.
| Group | Haemoglobin threshold for anaemia |
|---|---|
| Men (over 15 years) | < 130 g/L |
| Non-pregnant women (over 15 years) and children 12–14 years | < 120 g/L |
| Pregnancy – first trimester | < 110 g/L |
| Pregnancy – second and third trimester | < 105 g/L |
| Postpartum | < 100 g/L |
|
⚠️ Common pitfall • A normal MCV does not exclude iron deficiency. • Microcytosis is a late feature. • A coexisting cause of macrocytosis (B12 or folate deficiency, alcohol, chronic disease) can pull the MCV back into range. • If iron deficiency is plausible, check ferritin rather than waiting for the red cells to turn microcytic. |
Source: BSG · World Health Organization
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