Blood transfusion risks

Understand the risks involved in a blood transfusion.

Overall, a blood transfusion is very safe. Our stringent screening and testing of donated blood limit the risks involved. However, some small risks still exist.

Transmitted infections risk

In Singapore, the current estimated risk for contracting a major infection through blood transfusions is small:

  • One per 110,000 donations for Hepatitis B
  • One per 1,300,000 donations for Hepatitis C
  • One per 1,100,000 donations for HIV

Such infections could be due to the blood being tested during the early stages of infection (infectious window period), when the levels of virus are too low to be detected.

Not all infections can be detected. For example, screening tests for malaria, variant Creutzfeld Jakob Disease (vCJD) and dengue are either not available or not sensitive enough.

Similarly, there are no available tests for new and unknown infectious agents.


Mild reactions may include:

  • Rashes or hives – about 1-3% of transfusions
  • Fever – about 0.1-1% of transfusions

These usually subsidise quickly after the transfusion is stopped and are easily treated with medication.

These could be due to an allergy to the donated blood, or being given the wrong blood type. Hospital staff are trained to recognise and manage such reactions.

Severe reactions to blood transfusions are rare.


Serious complications following a transfusion are very rare.

  • Excessive fluid in the body and lungs (less than 1% of transfusions)
    • Leads to shortness of breath
    • Patients with heart or kidney problems may be at greater risk
  • Transfusion Related Acute Lung Injury (TRALI) (less than 0.02% of transfusions)
    • Leads to difficulty in breathing
  • Life-threatening complications (less than 0.02% of transfusions)
    • Due to incompatible blood group products
  • Potentially life-threatening severe allergic reactions (less than 0.005% of transfusions)
  • Potentially life-threatening bacterial infections (less than 0.002% of transfusions)
    • These may be unavoidable despite stringent precautions