Guidelines on Blood Transfusion

This guideline promotes best practice regarding blood use. Further information on blood transfusion, including details regarding sampling, administration, blood products and management of reactions is available on NHSGGC StaffNet by searching 'Blood Transfusion Information'.

Indications for transfusion

Acute blood loss

An acute blood loss of greater than 20% of blood volume (about 1000ml blood) will often need a transfusion though it should be guided by measured Haemaglobin (Hb) levels when available. Do not delay ordering blood in situations where blood loss is acute and rapid. If blood loss is very rapid, follow the site specific protocol for dealing with major haemorrhage.

For surgical patients

Consider transfusion if:

  • Post-operative Hb falls below 80g/L.
  • Pre-operative Hb is less than 90g/L and the surgery is associated with the probability of significant blood loss, but see point below. If surgery cannot be delayed for investigation, the timing of any transfusion should be discussed with the anaesthetist concerned as they may prefer to transfuse intra-operatively. It is also essential to be aware of the risk of Transfusion Associated Cardiac Overload (TACO) in this setting. 
  • Pre-operative anaemia must be investigated, as medical management may be more appropriate than transfusion.
  • Seek to maintain Hb above 80g/L (consideration of above 100g/L in patients with significant comorbidity e.g. age over 70 years with co-morbidity, ischaemic heart disease, valvular heart disease and peripheral vascular disease). Always reassess indications for any further transfusions after each unit is administered. 

Anaemia in active myocardial infarction

Hb <100g/L – Transfusion to an Hb of 100g/L is desirable but to overshoot to 110g/L may be excessive. Evaluate effect of each unit as it is given.

Anaemia in other patients

Some anaemias will respond to treatment of deficiency e.g. iron, B12, folate. Always consider cause before transfusing.

Hb <80g/L – Consider transfusion, but evaluate after each unit.

Hb 80–100g/L and normovolaemic patients – Consider transfusion only if they have symptomatic anaemia or significant comorbidity.

Symptoms and signs of anaemia include:

  • Shortness of breath for no other reason
  • Angina
  • Syncope
  • ST depression on ECG
  • Tachycardia for no other reason

Transfusion to an Hb above 100g/L is rarely indicated and the reason must be documented. Transfusion when Hb is already >100g/L is seldom indicated. 

Important notes

  • Think before transfusion. Blood is a biological product and sometimes is in short supply. Transfusions come with the potential for known and unknown risks.
  • Reassess after each unit is given. Do you need to give more?
  • Stop if symptoms / signs of anaemia noted above resolve
  • Stop if you have reached an adequate Hb i.e. above 80g/L in symptomless patients (100g/L in acute MI).

Further Information

Further information, including educational links, is available on NHSGGC StaffNet by searching under 'Blood Transfusion'.


Content last reviewed July 2020