The bone marrow

Stem cells are cells at a very early stage of development. All the blood cells in the body develop from stem cells. A type of stem cell called a myeloid stem cell can make:

• red blood cells, which carry oxygen to all cells in the body
• white blood cells called granulocytes, which are essential for fighting infection
• platelets, which help the blood to clot and control bleeding.

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:

The figures might look complicated when they’re written down, but in practice they are used in a straightforward way. For example, you’ll hear doctors or nurses saying things like: ‘your haemoglobin is 14’ or ‘your neutrophils are 4’. Many people with AML soon get used to these figures and what they mean.

The figures can vary a little from hospital to hospital. They can also be slightly different in people from African-Caribbean and Middle Eastern origin.

White blood cells

There are different types of white blood cell. The two main types are granulocytes and lymphocytes and these work together to fight infection.

Blood cells go through various stages of development before they are fully mature and able to work. Normally, while blood cells are developing, they stay inside the bone marrow. Once they are mature, they leave the bone marrow and enter the bloodstream.

Some types of blood cells only live for a few hours or a few days, so the bone marrow is constantly making new cells. The bone marrow normally makes millions of blood cells every day. This process is usually controlled with cells dividing to produce new cells as they are needed.