Anaemia

Severity

Range

Mild
Hb 100–119 (F) / 100–129 (M)
Moderate
Hb 80–99
Severe
Hb < 80 or symptomatic / active bleed

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GI / blood loss Causes

Upper GI bleed (ulcer, varices, Mallory-Weiss)Lower GI bleed (diverticular, colorectal Ca, angiodysplasia)Occult colon cancer in any iron-deficient older patientMenorrhagia, post-partum haemorrhageTrauma, surgical / retroperitoneal bleed

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Nutritional / GI absorption Causes

Iron deficiency — poor diet, coeliac, gastrectomy, H. pyloriB12 deficiency — pernicious anaemia, ileal disease, metforminFolate — alcohol, pregnancy, anti-folates (methotrexate)Chronic alcoholism (mixed picture)

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Chronic disease / renal Causes

Anaemia of chronic disease (infection, RA, malignancy)CKD (low erythropoietin)Hypothyroidism

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Haematological / marrow Causes

Myelodysplasia, aplastic anaemia, leukaemia infiltrationMultiple myelomaThalassaemia, sickle cell

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Haemolysis Causes

Autoimmune (warm / cold AIHA)Hereditary (G6PD, spherocytosis, sickle)MAHA (TTP, HUS, DIC, mechanical valve)Drug-induced (penicillins, cephalosporins, methyldopa)

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Drugs Causes

NSAIDs, aspirin, anticoagulants (GI bleed)Methotrexate, trimethoprim, phenytoin (folate / marrow)Chemotherapy, linezolid (marrow suppression)PPI (long-term — B12)