Blood components

Blood is often separated into its individual components, so patients can be given what they need, for example red blood cells or platelets.

This is called blood component therapy. It means we make the most of every blood donation, as the components in one unit of blood (or one donation) can be used to treat different patients.

Red blood cells

Red blood cells contain haemoglobin, which distributes oxygen to body tissues, and carries waste carbon dioxide back to the lungs.

Red blood cells are used to treat all kinds of anaemia (where people have low haemoglobin levels) including:

  • as a result of rheumatoid arthritis or cancer
  • when red cells break down in newborn babies
  • sickle cell disorder

Red blood cell transfusions replace the heavy blood loss that can occur in an accident, during surgery or in childbirth.

White blood cells

White blood cells fight infection and are part of the body's defence system. White cell transfusions may be given to patients suffering from life-threatening infections whose normal defence mechanisms don't seem to be responding to antibiotics.


Platelets are crucial in helping blood to clot: they do this by clumping together to stop bleeding after an injury. They can be used:

  • to treat cases of bone marrow failure
  • following a transplant or chemotherapy treatments
  • to treat leukaemia

Find out about switching from giving blood to platelets


Plasma is the fluid that carries all blood cells and components. Plasma contains a large number of proteins and substances which are often important ingredients in medicinal products.