Synopsis
Decide when red-cell transfusion is justified, apply UK restrictive thresholds safely, prescribe an appropriate dose and reassess benefit while treating the cause of anaemia.
- Red cells improve oxygen-carrying capacity; they do not replace iron, stop haemorrhage or treat the mechanism causing anaemia.
- First-line decision-making combines haemoglobin, symptoms, bleeding trajectory, cardiopulmonary reserve and the likelihood that a reversible cause can be treated safely without transfusion.
- For stable adults without major haemorrhage, acute coronary syndrome or a chronic transfusion programme, NICE recommends a restrictive threshold of 70 g/L and a post-transfusion target of 70–90 g/L.
- For acute coronary syndrome, consider a threshold of 80 g/L and a target of 80–100 g/L; evidence is less certain, so integrate ongoing ischaemia and specialist advice.
- For chronic transfusion-dependent anaemia, set an individual threshold and target with the specialist team rather than repeatedly applying 70 g/L.
- First-line dose for a stable, non-bleeding adult is one unit, followed by clinical reassessment and a haemoglobin measurement before another unit is prescribed.
- One adult unit commonly raises haemoglobin by about 10 g/L in a 70 kg non-bleeding adult, but size, ongoing loss, haemolysis and fluid balance alter the increment.
- Use weight-adjusted or paediatric-volume prescribing for low-body-weight adults and children; a fixed unit can cause circulatory overload.
- Do not transfuse a number in isolation: well-compensated chronic anaemia may tolerate a low value, whereas acute blood loss can be dangerous before haemoglobin has fallen.
- Treat iron, vitamin B12 or folate deficiency and investigate bleeding; transfusion is a bridge when the deficit is urgent, severe or cannot wait for haematinic response.
- Explain indication, expected benefit, material risks, alternatives and the option to refuse, and document valid consent unless an immediate emergency prevents it.
- Every unit needs positive bedside identification, an authorised prescription, observations before and during transfusion and a documented assessment of response.
Key red flags
Active major haemorrhage, haemodynamic instability or ongoing rapid blood loss invalidates routine restrictive-threshold algorithms and requires a haemorrhage protocol.
Chest pain, ischaemic ECG change, syncope, resting dyspnoea, heart failure, shock, rising lactate or altered consciousness may indicate inadequate oxygen delivery requiring urgent individual assessment.
A falling haemoglobin without visible bleeding suggests occult gastrointestinal, retroperitoneal, obstetric or surgical loss, haemolysis, haemodilution or repeated sampling and demands cause-finding.
A previous severe reaction, clinically significant antibody, IgA-related reaction risk or irradiation requirement must be communicated before issue; complex compatible units may take time.
Transfusion-associated circulatory overload risk is increased by cardiac or renal impairment, low body weight, positive fluid balance and severe chronic anaemia; prescribe slowly and reassess.
Investigation priorities
Confirm anaemia, define indices and establish rate of change.
Determine whether anaemia is causing current physiological compromise.
Management branches
Haemoglobin approaches 70 g/L without major haemorrhage, ACS or a chronic programme.
- Assess symptoms, trajectory, reserve, reversible cause and patient preference rather than transfusing automatically.
- If transfusion is justified, prescribe one appropriately selected unit at a safe rate with consent and baseline observations.
- Reassess symptoms and haemoglobin after the unit; prescribe another only if the original indication remains and the target has not been met.
Iron, vitamin B12 or folate deficiency explains stable anaemia.
- Assess severity, symptoms, ongoing loss and the time available for haematological response.
- Start appropriate replacement and investigate the source, using intravenous iron when oral treatment is unsuitable or too slow under NICE criteria.
- Use red cells only when clinical urgency or inadequate reserve makes waiting unsafe; continue replacement after transfusion.