Synopsis
Assess anaemia by physiological impact, cell size and marrow response, identify bleeding or haemolysis promptly and reach an aetiological diagnosis rather than treating haemoglobin alone.
- Confirm anaemia against the laboratory's age-, sex- and pregnancy-appropriate reference interval, then compare prior haemoglobin and ask whether the change is acute, chronic or acute on chronic.
- Grade urgency from symptoms, haemodynamics, ongoing bleeding, cardiac or respiratory reserve and speed of fall rather than using a universal transfusion trigger for every patient.
- Use mean cell volume as an organising clue, not a diagnosis. Mixed iron and B12 deficiency, transfusion, reticulocytosis or thalassaemia can make the average cell size deceptively normal.
Key red flags
Resting dyspnoea, chest pain, syncope, heart failure, shock or neurological symptoms with a rapid haemoglobin fall indicate compromised oxygen delivery and urgent support needs.
Investigation priorities
Confirm anaemia, identify mixed populations and detect urgent marrow or haemolytic morphology.
Management branches
Anaemia accompanies shock, active bleeding, ischaemic symptoms, syncope, heart failure or rapid clinical deterioration.
- Use ABCDE, identify and control bleeding, obtain FBC, coagulation, group and screen or crossmatch, renal, liver, blood gas and cause-directed samples, and activate major-haemorrhage support when indicated.
- Preferred transfusion practice is individualised, component appropriate and reassessed after each step; alternatives such as haemostasis, iron or B12 cannot replace immediate red-cell support when oxygen delivery is failing.
Anaemia is confirmed and the patient is stable enough for a structured causal assessment.