01Purpose and principlesWhat the treatment does and how it fits into care.
Anaemia reduces arterial oxygen content, but clinical harm depends on more than haemoglobin. Compensatory tachycardia, increased stroke volume and oxygen extraction may maintain delivery in gradual anaemia; abrupt haemorrhage also removes circulating volume and can cause shock before laboratory equilibration reveals the true red-cell loss. Review symptoms at rest and exertion, rate of change, bleeding, cardiac or respiratory disease, sepsis, fever and anticipated procedures. Transfusion is justified when likely oxygen-delivery benefit exceeds immunological, infectious, circulatory and administrative risk.
The UK default for most stable adults is restrictive practice. NICE recommends considering a threshold of 70 g/L with a target of 70–90 g/L after transfusion when the patient does not have major haemorrhage, acute coronary syndrome or a condition requiring regular transfusions. This is a decision point, not an automatic trigger. At 68 g/L a comfortable, stable patient with correctable iron deficiency may reasonably receive iron and observation; a breathless patient with poor reserve may benefit from a unit after assessment. Equally, transfusing to a normal population haemoglobin is rarely necessary.
Acute coronary syndrome is treated differently because coronary oxygen supply may be critically limited. NICE advises considering a threshold of 80 g/L and target 80–100 g/L. Confirm that symptoms represent active acute coronary syndrome rather than using the threshold for stable historical coronary disease. Discuss persistent ischaemia, heart failure and competing TACO risk with cardiology and transfusion specialists. Do not extrapolate this target automatically to every patient with vascular risk or a raised troponin from sepsis.
Patients on planned long-term red-cell support need disease-specific goals. In transfusion-dependent thalassaemia, marrow-failure syndromes, sickle-cell exchange programmes or selected myelodysplasia, thresholds reflect symptoms, suppression of ineffective erythropoiesis, HbS percentage, quality of life and iron burden. Use an agreed individual plan, extended antigen matching where indicated and longitudinal surveillance for alloantibodies and iron overload. A one-off ward threshold can disrupt a carefully designed programme.
Dose is part of the indication. In a stable adult without active bleeding, prescribe one unit and reassess before deciding on another. Document the clinical question: relief of limiting dyspnoea, correction before a defined procedure or support while urgent treatment takes effect. Measure the haemoglobin after equilibration according to urgency and local practice and compare the actual increment with expectation. Failure to rise suggests ongoing loss, haemolysis, sampling timing, dilution or an incorrect assumption about the starting value.
Before ordering blood, identify and treat the cause. Check indices and film, reticulocytes, ferritin and iron studies, vitamin B12 and folate, renal and liver function and haemolysis tests as directed by the presentation. Look actively for gastrointestinal, menstrual, obstetric, operative or urinary blood loss. Oral iron is appropriate first-line for many stable iron-deficiency states; intravenous iron is useful when oral therapy is not tolerated, absorbed or fast enough. Vitamin replacement and disease-specific treatment provide durable recovery, whereas donor cells last only weeks.
Risk reduction begins before issue. Review past reactions and antibodies, pregnancy and transfusion history, cardiac and renal status, body weight, fluid balance and special-component requirements. Obtain valid consent and a correctly labelled sample. Prescribe a rate and observation schedule rather than merely a unit count. For TACO-prone patients, use the minimum dose, slower administration compatible with product limits, reassessment and an individually justified diuretic plan; prophylactic furosemide is not a substitute for avoiding unnecessary blood.
Assess effectiveness clinically as well as numerically. Improvement in symptoms, heart rate, perfusion or exercise tolerance should match the stated aim. Fever, rigors, pain, dyspnoea, wheeze, hypotension, hypertension, dark urine or distress during transfusion requires stopping the component, keeping intravenous access with compatible fluid, urgent ABCDE review, identity checks and contact with the transfusion laboratory. Resume only if a trained clinician and local reaction protocol establish that doing so is safe.
Key points
- 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.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
No active bleeding or acute coronary syndrome, stable observations and haemoglobin around or below 70 g/L prompt symptom-led consideration rather than automatic transfusion.
Active myocardial ischaemia changes the considered threshold to 80 g/L and target to 80–100 g/L, balanced against overload risk.
Tachycardia, hypotension, poor perfusion or ongoing bleeding makes physiology and haemorrhage control more important than an initially preserved haemoglobin.
Gradual fatigue with stable physiology permits cause-directed treatment and an individual decision; tolerance of a low value does not remove the need for investigation.
A smaller-than-expected rise suggests ongoing haemorrhage, haemolysis, dilution, mistimed sampling or an inaccurately measured baseline.
Heart or kidney dysfunction, positive balance, low weight or severe chronic anaemia supports one-unit dosing, slower rate and close respiratory review.
03Assessment before treatmentTests and checks that guide safe selection.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
First-line: full blood count and trendFirst stepFirst line - Why
- Confirm anaemia, define indices and establish rate of change.
- Interpretation and limitations
- Interpret haemoglobin with baseline, volume state and bleeding; microcytosis, macrocytosis, other cytopenias and an unexpected fall direct cause-specific testing.
- 02
First-line: clinical oxygen-delivery assessmentFirst line - Why
- Determine whether anaemia is causing current physiological compromise.
- Interpretation and limitations
- Record symptoms, observations, perfusion, bleeding, cardiopulmonary reserve and ECG when ischaemia is possible; a stable number alone does not establish benefit.
- 03
Group, antibody screen and compatibility testing - Why
- Provide safely matched units and detect alloantibodies before transfusion.
- Interpretation and limitations
- Historical antibodies remain binding; inform the laboratory of urgency, transfusion history and irradiation, washing or other component requirements.
- 04
Cause-directed haematinics and reticulocytes - Why
- Identify iron, vitamin B12 or folate deficiency and assess marrow response.
- Interpretation and limitations
- Low ferritin supports iron deficiency, but inflammation can elevate ferritin; interpret transferrin saturation, indices and clinical context together.
- 05
Haemolysis screen when indicated - Why
- Detect shortened red-cell survival causing anaemia or poor transfusion increment.
- Interpretation and limitations
- Reticulocytosis, unconjugated bilirubin and LDH elevation with low haptoglobin support haemolysis; DAT and film help distinguish immune and mechanical causes.
- 06
Post-transfusion haemoglobin - Why
- Quantify response before prescribing another unit in a stable non-bleeding patient.
- Interpretation and limitations
- Expect roughly 10 g/L per adult unit in a 70 kg patient; assess timing, size, fluid, bleeding and haemolysis if the result differs.
04Treatment approachPreparation, options, escalation and aftercare.
01Stable non-bleeding anaemiaUse a restrictive, one-unit strategyFirst stepHaemoglobin approaches 70 g/L without major haemorrhage, ACS or a chronic programme.+
- 1Assess symptoms, trajectory, reserve, reversible cause and patient preference rather than transfusing automatically.
- 2If transfusion is justified, prescribe one appropriately selected unit at a safe rate with consent and baseline observations.
- 3Reassess symptoms and haemoglobin after the unit; prescribe another only if the original indication remains and the target has not been met.
02Acute coronary syndromeUse the ACS-specific decision pointActive ACS coexists with anaemia near or below 80 g/L.+
- 1Confirm ongoing ischaemic context and assess heart failure, bleeding and TACO risk.
- 2Consider one unit with a target of 80–100 g/L, using cardiology or transfusion advice where benefit and overload compete.
- 3Reassess pain, ECG, haemoglobin and respiratory status before any further unit.
03Major haemorrhagePrioritise haemostasis and protocolised resuscitationActive bleeding causes shock or threatens rapid circulatory collapse.+
- 1Activate the local major-haemorrhage protocol and achieve procedural, surgical, endoscopic or obstetric haemorrhage control.
- 2Use emergency red cells and balanced components according to the clinical pathway; do not wait for a threshold haemoglobin.
- 3Change from empirical packs to laboratory or viscoelastic-guided therapy early and prevent hypothermia, acidosis and hypocalcaemia.
04Treatable deficiencyCorrect the cause and reserve blood for urgencyIron, vitamin B12 or folate deficiency explains stable anaemia.+
- 1Assess severity, symptoms, ongoing loss and the time available for haematological response.
- 2Start appropriate replacement and investigate the source, using intravenous iron when oral treatment is unsuitable or too slow under NICE criteria.
- 3Use red cells only when clinical urgency or inadequate reserve makes waiting unsafe; continue replacement after transfusion.
05High overload riskMinimise dose and rateCardiac or renal dysfunction, low weight, positive balance or severe chronic anaemia increases TACO probability.+
- 1Verify that transfusion is necessary and prescribe one unit or a weight-adjusted volume.
- 2Use a slower rate within component and local limits, monitor closely and consider diuretic only after individual volume assessment.
- 3Stop and assess immediately if breathlessness, hypoxia, hypertension, raised JVP or pulmonary oedema develops.
05Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- Record temperature, pulse, blood pressure, respiratory rate and oxygen saturation immediately before transfusion and at the locally required intervals, including an early observation after starting.
- Remain alert for fever, rigors, pain, rash, wheeze, dyspnoea, hypotension, hypertension, dark urine or anxiety throughout and after the unit.
- For stable non-bleeding adults, check haemoglobin and clinical response after each unit before authorising another.
- Track fluid input, urine output, weight and respiratory findings in patients at risk of TACO; escalation may require oxygen, imaging and diuresis.
- Document the donation number, start and completion time, staff checks, adverse events and whether the intended symptom or target improved.
- Continue investigation and treatment of the cause, including response to haematinics, bleeding control and long-term iron burden in chronically transfused patients.
06Special situationsVariants, exceptions and circumstances that change the usual approach.
A threshold is a prompt
NICE values support consideration and targets; they do not replace symptoms, bleeding rate, reserve or informed preference.
Acute loss can hide
Haemoglobin concentration may remain initially normal after whole-blood loss until redistribution or fluid replacement changes plasma volume.
One unit is an active review point
Single-unit prescribing works only if clinical and laboratory reassessment occurs before another component is released.
The target is not normality
Restrictive targets aim for adequate oxygen delivery while limiting exposure, not restoration to a healthy reference interval.
Small patients receive a larger dose
A standard adult unit produces a greater circulating-volume and haemoglobin effect in low-body-weight patients, increasing overload risk.
Transfusion can obscure diagnosis
Donor cells change indices, film, haemoglobin electrophoresis and some haemolysis results; obtain essential diagnostic samples first when safe.
07Common pitfallsFrequent interpretation and management errors.
- 01
Do not transfuse solely because haemoglobin is below a round number.
- 02
Do not apply the 70 g/L threshold during major haemorrhage or active acute coronary syndrome.
- 03
Do not routinely prescribe two units before observing the effect of one in a stable non-bleeding adult.
- 04
Do not use red cells as definitive treatment for uncomplicated iron, vitamin B12 or folate deficiency.
- 05
Do not aim for a normal haemoglobin when the evidence-based target is lower.
- 06
Do not forget low body weight, cardiac function, renal function and fluid balance when choosing volume and rate.
- 07
Do not allow an urgent request to bypass correct patient identification and sample labelling.
- 08
Do not ignore a poor post-unit increment; investigate bleeding, haemolysis, dilution and sampling timing.
- 09
Do not omit consent, alternatives and documentation because transfusion is familiar.