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Blood Transfusions

Medically reviewed by: Larissa Hirsch, MD

What Is a Blood Transfusion?

A blood transfusion is when a donor's blood is given to a patient. Blood transfusions save lives every day. Hospitals use them to help people who are injured, having surgery, getting cancer treatments, or being treated for other diseases that affect the blood, like sickle cell anemia.

What Is Blood Made of?

Blood is a mixture of cells and liquid, and each part has a specific job:

  • Red blood cells carry oxygen to the body's tissues and remove carbon dioxide. These cells are the ones that are most commonly transfused.
  • White blood cells help the body fight infection.
  • Platelets, the smallest blood cells, help blood to clot and control bleeding.
  • Plasma, the pale yellow liquid part of blood, is a mix of water, proteins, electrolytes, carbohydrates, cholesterol, hormones, and vitamins.