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.
- Absolute reticulocytes provide the crucial production branch: an appropriate rise suggests bleeding or haemolysis, while a low response suggests nutrient, renal, inflammatory, endocrine or marrow limitation.
- Microcytosis most often reflects iron restriction or haemoglobinopathy; macrocytosis directs B12, folate, alcohol, liver, thyroid, reticulocyte, medicine and marrow assessment; normocytosis includes early forms of both.
- Prove iron deficiency and seek its cause. In adult men and postmenopausal women, gastrointestinal blood loss and cancer require explicit consideration rather than indefinite iron without investigation.
- Confirm haemolysis through a concordant pattern of reticulocytes, bilirubin, LDH, haptoglobin and film, then use the direct antiglobulin test and morphology to separate immune, enzyme, membrane and mechanical causes.
- Transfusion treats oxygen-delivery risk but does not diagnose or correct the underlying process. Record the reason, alternatives, target and reassessment after each transfusion decision.
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.
Low reticulocytes, additional cytopenias, blasts, teardrops, dysplasia, constitutional symptoms or organ enlargement raises aplasia, infiltration, myelodysplasia or leukaemia.
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.
- Escalate ongoing bleeding, cardiovascular compromise, severe haemolysis or pregnancy-related instability to the relevant surgical, obstetric, haematology and critical-care teams.
Anaemia is confirmed and the patient is stable enough for a structured causal assessment.
- Review tempo, blood loss, diet, medicines, alcohol, family and ethnic history and all lineages, then obtain film, absolute reticulocytes, ferritin, transferrin saturation, B12 and folate.
- For low reticulocytes, the first-line pathway is substrate, renal, inflammatory, thyroid and marrow assessment; for high reticulocytes, the preferred route is bleeding and haemolysis testing.