Anaemia is one of the most common clinical findings. 🩸 It often requires detective work to uncover the underlying cause. Remember: anaemia is a sign, not a diagnosis.

🔍 Definition

Men: Hb < 13 g/dL
Women: Hb < 11 g/dL

📊 Causes by MCV

Microcytic (MCV < 80 fL): Iron deficiency anaemia, Thalassaemia, AOCD, Sideroblastic anaemia.
Macrocytic (MCV > 96 fL): Megaloblastic: B12 deficiency, Folate deficiency Normoblastic: Alcoholism, liver disease, hypothyroidism, marrow disorders, drugs (e.g. azathioprine).
Normocytic (MCV 80–96 fL): Acute blood loss, haemolysis, marrow infiltration/fibrosis, CKD, endocrine disease, AOCD.

📑 Classification of Anaemia

Category	Examples
Microcytic (MCV < 80 fL)	Iron deficiency anaemia (IDA) Thalassaemia Anaemia of chronic disease (AOCD) Sideroblastic anaemia
Macrocytic (MCV > 96 fL)	Megaloblastic B12 deficiency (pernicious anaemia, Crohn’s/ileal disease, dietary) Folate deficiency (nutrition, alcoholism, pregnancy) Normoblastic Alcoholism Reticulocytosis (bleeding or haemolysis) Liver disease Hypothyroidism Azathioprine and other drugs Myelodysplasia / acute leukaemia Aplastic anaemia
Normocytic (MCV 80–96 fL)	Acute blood loss Haemolysis Marrow infiltration/fibrosis Anaemia of chronic disease (AOCD) Endocrine disease (e.g. hypothyroidism, adrenal insufficiency) Chronic kidney disease Autoimmune disease

🩺 Clinical Features

Fatigue, pallor, exertional dyspnoea
Angina or heart failure if severe
Pica (ice, soil, paper) in iron deficiency
Neurological: peripheral neuropathy, ataxia in B12 deficiency

🧪 Investigations

FBC + film: Hb, MCV, morphology, WCC, platelets (pancytopenia → marrow disease).
U&E: CKD common cause of normocytic anaemia.
Iron studies: Ferritin low in IDA, but ↑ with inflammation.
Hb electrophoresis: β-thalassaemia trait → raised HbA₂.
B12 & folate: Detect macrocytosis; intrinsic factor Abs for pernicious anaemia.
Autoimmune screen if systemic cause suspected.
TTG/biopsy: Coeliac malabsorption if suspected.

💊 Management

IDA: Oral ferrous sulphate — always investigate source (e.g. GI bleed in older adults).
B12 deficiency: IM hydroxocobalamin (lifelong in pernicious anaemia).
Folate deficiency: Oral folic acid (exclude B12 deficiency first).
Thalassaemia trait: Stable microcytosis — do not give iron unless deficiency co-exists.
CKD: Consider erythropoiesis-stimulating agents.
Treat underlying causes (e.g. malignancy, autoimmune, chronic inflammation).

📚 References

💡 Clinical Pearl: MCV is the quickest way to classify:

Microcytic → "TICS" (Thalassaemia, Iron deficiency, Chronic disease, Sideroblastic)
Macrocytic → B12/folate vs alcohol/liver
Normocytic → blood loss, CKD, marrow disease

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Anaemia: Assessment