The blood

To help you understand CML and its treatment, it is useful to know a bit about your blood, how it’s made and what it does.

Blood is made up of blood cells, which move around in a liquid called plasma. Blood cells are made in the bone marrow. This is a spongy material in the middle of our bones – particularly in our pelvis and backbone (spine). Normally, millions of new blood cells are made every day to to keep the body healthy.

Bone marrow
Bone marrow

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Bone marrow

All blood cells are made from cells called blood stem cells.

There are two types of blood stem cell:

  • lymphoid stem cells, which make a type of white blood cell called lymphocytes
  • myeloid stem cells, which make all the other types of blood cell: red blood cells, platelets, and white blood cells.

Blood stem cells in the bone marrow divide and grow to make new blood cells. The new, developing blood cells are called blast cells. They don’t look like fully developed cells and they can’t do the jobs that fully developed cells do. Usually, blast cells stay in the bone marrow until they have developed into red blood cells, platelets or white blood cells.

How blood cells divide

Blood cells
Blood cells

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The mature cells are then released into your blood to carry out different functions: 

  • Red blood cells contain haemoglobin (Hb), which carries oxygen from your lungs to all the cells in your body. 
  • Platelets are very small cells that help blood to clot, and prevent bleeding and bruising.
  • White blood cells fight and prevent infection. There are several types of white blood cell. The two most important types are neutrophils and lymphocytes.
The levels of these cells in your blood are measured in a blood test called a full blood count (FBC). The figures below are a guide to the levels usually found in a healthy person.
Type of blood cellLevels found in a healthy person
Red blood cells (measured in haemoglobin Hb levels)130–180g/l (men)
115–165g/l (women)
Platelets150–400 x 109/l
White blood cells (WBC)4.0–11.0 x 109/l
Neutrophils2.0–7.5 x 109/l
Lymphocytes1.5–4.5 x 109/l

These figures vary from hospital to hospital. Your doctor or nurse will be able to tell you which levels they use. They can also vary slightly between people from different ethnic groups. The figures might look difficult, but they’re used in a straightforward way. For example, you will hear doctors or nurses saying things like: ‘your platelets are 150,’ or ‘your neutrophils are 4’. You will probably find you get used to these figures and what they mean. Remember, you can always ask your doctor or nurse if you are unsure.

Back to Understanding chronic myeloid leukaemia (CML)

What is CML?

Chronic myeloid leukaemia (CML) is a rare type of cancer. It causes the body to make too many white blood cells.

Symptoms of CML

Not everyone has symptoms. Any symptoms that occur are usually mild and similar to common illnesses such as flu.