There are two different types of stem-cell transplant:

• high-dose treatment with stem-cell support
• allogenic (donor) stem-cell transplant

To understand these treatments, it helps to first understand how bone marrow and stem cells work.

Stem cells are blood cells in their earliest stage of development. All blood cells develop from stem cells. The full name of stem cells in the blood and bone marrow is hematopoietic stem cells.

Bone marrow is a spongelike material found inside bones, especially those of the pelvis. The bone marrow is the place where stem cells are made.

Most of the time, almost all of the stem cells can be found in the bone marrow. There is usually a low number of these in the blood. Stem cells remain in the bone marrow while they develop into blood cells. Then, once they have matured completely, they are released into the bloodstream.

The three main types of blood cells are:

Red blood cells – These contain hemoglobin (Hb), which transports oxygen to all the cells in the body.

White blood cells – These fight against infection. There are several types of white blood cell. The two most important are neutrophils and lymphocytes.

Platelets – these help blood to clot and prevent bleeding.

The levels of blood cells in the blood are measured using a test called a blood count.

The figures below are a guide to the levels normally found in healthy individuals.

These figures can change from hospital to hospital. Your doctor or nurse can tell you what levels they use. They can also vary slightly between people from different ethnic groups.

Most people with cancer or leukemia quickly get used to these levels and what they mean. But you should always ask your medical team if you aren't sure.