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 Haemoglobin (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:

  • 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, particularly if the patient is asymptomatic.
  • Seek to maintain Hb above 70g/L with a target range of 70-90g/L post transfusion (consideration of above 80g/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 aiming for a target range of 80 - 100g/L). Always reassess indications for any further transfusions after each unit is administered. 

Anaemia in active myocardial infarction

Hb <80g/L – Transfusion to an Hb of 80 - 100g/L is desirable. Evaluate effect of each unit as it is given. In patients who may have impaired cardiac function, be particularly aware of the risk of Transfusion associated Circulatory Overload (TACO). Investigation of the cause of anaemia is required. 

Anaemia in other patients

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

Hb <70g/L – Consider transfusion but evaluate after each unit.

Hb 70– 90g/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. 70 - 90g/L in symptomless patients (80 - 100g/L in acute MI).

Further Information

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


Guideline reviewed: October 2022

Page last updated: December 2022