If you are going to have surgery and expect to need a blood transfusion, you may want to bank your own blood a few weeks before the surgery. If you do need a transfusion, doctors can use your own blood.

Many people consider this choice to protect themselves from the risks of disease or mismatched blood that are linked to blood transfusion.

One risk of getting a blood transfusion is a transfusion reaction.

Transfusion reactions occur when the blood you are given does not match your blood type. This matching error is rare. The lab may mislabel a unit of blood. A doctor, nurse, or technician may misread the label before the blood is given to you.

Getting the wrong blood type happens rarely, up to 4 times for every 1 million units of blood transfused.^{footnote 1} A transfusion reaction may be mild or severe. A severe reaction can be life-threatening.^{footnote 2}

It's possible to have a mild transfusion reaction even if your blood and the blood you are given are matched correctly.

Some people, especially those who have had many blood transfusions, make antibodies against the blood they receive. Their immune system mistakes the new blood as harmful and tries to destroy it. Careful testing helps lower the risk for these problems.

The risk for an error in reading or labelling is the same whether you bank your own blood before surgery or receive a transfusion of donor blood. An error in reading or labelling may also mean that you receive the correct blood type during your surgery but not the blood you banked.

Getting a viral infection, such as hepatitis or HIV, from a blood transfusion is very rare in Canada. Guidelines enforced by Health Canada's Therapeutic Products Directorate (TPD) guard the collection, testing, storage, and use of blood. The risk of disease from a blood transfusion is higher in less developed countries.

It's possible for blood to become contaminated with bacteria during or after donation. Getting a transfusion with blood that contains bacteria can lead to a bacterial infection that affects your whole body. You face the same risk for bacterial infection whether you bank your own blood before surgery or receive a blood transfusion of donor blood.

Because blood can't be stored very long, you must bank your blood a few weeks before your surgery. This may not allow enough time for your body to make enough new blood to replace what you banked before surgery. You may have less blood than normal at the time of surgery, so your body may not be able to lose much more blood before needing a transfusion. In some cases, it's possible that you would not have needed a transfusion at all if you hadn't banked blood before surgery.

You may not be able to bank enough blood for your surgery. Most people are able to safely bank 2 to 4 units of blood before surgery. If you are having major surgery that may require more blood than this, you may need more than you can safely bank.

Talk with your surgeon about how much blood you might need for your surgery.