There are many reasons you may need a blood transfusion:

• After knee or hip replacement surgery, or other major surgery that results in blood loss
• After a serious injury that causes a lot of bleeding
• When your body cannot make enough blood

A blood transfusion is a safe and common procedure during which you receive blood through an intravenous (IV) line placed in one of your veins. It takes 1 to 4 hours to receive the blood, depending on how much you need.

There are several sources of blood, which are described below.

The most common source of blood is from volunteers in the general public. This kind of donation is also called homologous blood donation.

Many communities have a blood bank at which any healthy person can donate blood. This blood is tested to see if it matches yours.

You may have read about the danger of becoming infected with hepatitis, HIV, or other viruses after a blood transfusion. Blood transfusions are not 100% safe. But the current blood supply is thought to be safer now than ever. Donated blood is tested for many different infections. Also, blood centers keep a list of unsafe donors.

Donors answer a detailed list of questions about their health before they are allowed to donate. Questions include risk factors for infections that can be passed on through their blood, such as sexual habits, drug use, and current and past travel history. This blood is then tested for infectious diseases before it is allowed to be used.

This method involves a family member or friend donating blood before a planned surgery. This blood is then set aside and held only for you if you need a blood transfusion after surgery.

Blood from these donors must be collected at least a few days before it is needed. The blood is tested to see if it matches yours. It is also screened for infection.

Most of the time, you need to arrange with your hospital or local blood bank before your surgery to have directed donor blood.

It is important to note that there is no evidence that receiving blood from family members or friends is any safer than receiving blood from the general public. In very rare cases, though, blood from family members can cause a condition called graft-versus-host disease. For this reason, the blood needs to be treated with radiation before it can be transfused.

Although blood donated by the general public and used for most people is thought to be very safe, some people choose a method called autologous blood donation.

Autologous blood is blood donated by you, which you later receive if you need a transfusion during or after surgery.

• You can have blood taken from 6 weeks to 5 days before your surgery.
• Your blood is stored and is good for a few weeks from the day it is collected.
• If your blood is not used during or after surgery, it will be thrown away.

DeSimone RA, Ness PM, Cushing MM. Principles of red blood cell transfusion. In: Hoffman R, Benz EJ, Silberstein LE, et al, eds. Hematology: Basic Principles and Practice. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 112.

Shimabukuro D, Miller RD. Blood therapy. In: Pardo M, ed. Miller's Basics of Anesthesia. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 25.

US Food and Drug Administration website. Blood and blood products. www.fda.gov/vaccines-blood-biologics/blood-blood-products. Updated March 7, 2023. Accessed September 15, 2023.