Anaemia is one of the most common findings in medicine – but it’s a sign, not a diagnosis. Here’s what every UK medical student needs to know.
Anaemia is defined as a reduction in haemoglobin concentration below the normal range for age and sex, leading to impaired oxygen delivery to tissues.
| Group | WHO Definition of Anaemia |
|---|---|
| Men | Hb < 130 g/L |
| Women (non-pregnant) | Hb < 120 g/L |
| Children (6 mo – 5 yrs) | Hb < 110 g/L |
| Pregnant women | Hb < 110 g/L |
💡 Always investigate the underlying cause — anaemia is rarely a diagnosis in itself.
| Type | MCV | Common Causes |
|---|---|---|
| Microcytic | < 80 fL | Iron deficiency, thalassaemia, sideroblastic anaemia, late-stage chronic disease |
| Normocytic | 80–100 fL | Acute blood loss, haemolysis, CKD, marrow failure, early chronic disease |
| Macrocytic | > 100 fL | B12 or folate deficiency, alcohol, liver disease, hypothyroidism, myelodysplasia |
🚨 MCV is a starting point — use clinical context and blood film to guide further tests.
Anaemia arises through one or more of the following mechanisms:
Decreased production: e.g. iron/B12/folate deficiency, marrow suppression
Increased destruction: e.g. haemolysis (autoimmune, hereditary)
Blood loss: e.g. trauma, GI bleeding, menorrhagia
Symptoms:
Fatigue
Dizziness or syncope
Breathlessness
Palpitations
Headache, poor concentration
Signs:
Pallor (especially conjunctivae)
Tachycardia, flow murmurs
Postural hypotension
Glossitis, koilonychia, angular stomatitis
Neurological signs (if B12 deficient)
🚨 Always examine for signs of chronic blood loss or haemolysis.
| Test | Purpose |
|---|---|
| FBC, MCV, MCH | Establish anaemia and classify |
| Reticulocyte count | Bone marrow activity |
| Blood film | Morphology clues (e.g. spherocytes, target cells) |
| Ferritin | Iron stores (note: acute phase reactant) |
| B12 & Folate | Macrocytic screen |
| CRP/ESR | Chronic disease/inflammation |
| U&Es, LFTs, TSH | Look for secondary causes |
| Haemolysis screen | LDH, haptoglobin, bilirubin, Coombs test |
💡 Ferritin is the best initial test for suspected iron deficiency — but can be falsely normal in inflammation.
| Type | Hallmarks | Typical Triggers |
|---|---|---|
| Iron Deficiency Anaemia | Microcytic, ↓ ferritin | Chronic GI blood loss, menstruation, malabsorption |
| Anaemia of Chronic Disease | Normocytic/microcytic, ↑ ferritin | IBD, RA, chronic infection or malignancy |
| B12 Deficiency | Macrocytic, glossitis, neuropathy | Pernicious anaemia, gastrectomy, veganism |
| Folate Deficiency | Macrocytic, no neurology | Alcoholism, pregnancy, methotrexate |
| Haemolytic Anaemia | ↑ LDH, ↓ haptoglobin, jaundice | AIHA, G6PD, sickle cell |
| CKD | Normocytic, ↓ EPO | Stage 3+ CKD |
🚨 Unexplained anaemia in older adults should raise concern for GI malignancy.
| Cause | Key Focus |
|---|---|
| Iron deficiency | Iron replacement + source investigation |
| B12 deficiency | IM replacement (monitor for neuro signs) |
| Folate deficiency | Oral folate after B12 correction |
| ACD | Control underlying disease ± EPO (in CKD) |
| Haemolysis | Identify and treat cause (e.g. steroids, folate) |
| CKD-related | Iron + EPO (if iron replete) |
💡 Never give folate before correcting B12 — this can mask and worsen neurological damage.
Microcytic anaemia? Think TICS: Thalassaemia, Iron deficiency, Chronic disease (late), Sideroblastic
Macrocytic? Think B12, folate, alcohol, liver disease, hypothyroidism, myelodysplasia
Always check ferritin before labelling someone as iron deficient
Reticulocyte count = 🔑 for distinguishing underproduction vs haemolysis
Anaemia + jaundice = consider haemolysis
Fatigue + glossitis + neuropathy = think B12
This is just the clinical summary. The full Medifries textbook chapter includes:
Full drug regimens, routes, and safety tips
Investigation trees (IDA vs ACD vs haemolysis vs macrocytic)
Management algorithms by cause
Lab pattern tables for haematology differentials
SBA-style practice questions
Active recall flashcards
