Blood tests

There are many different types of blood test. You may have blood samples taken to check your general health and how well your liver and kidneys are working.

What is a blood test?

There are many different types of blood test. Your doctor will decide which tests you need. Blood tests can check:

  • the number of different blood cells – white blood cells, red blood cells and platelets you have in your blood (blood count)
  • how organs such as your liver and kidneys are working
  • for abnormal levels of proteins, called tumour markers
  • the levels of other substances in the blood that may be linked with certain types of cancer.

A phlebotomist, nurse or doctor will take a sample of blood, usually from a vein in your arm. This will then be tested in a laboratory.

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Full blood count (FBC)

Blood is made up of blood cells, which float in a liquid called plasma. Each type of blood cell has an important role in the body.

A full blood count (FBC) test measures the level of these cells:

  • Red blood cells

    Red blood cells contain haemoglobin (Hb), which carries oxygen from your lungs to all the cells in your body.

  • Platelets

    Platelets are very small cells that help blood to clot, and prevent bleeding and bruising.

  • White blood cells

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

Measuring your full blood count

The levels of these cells in your blood can be measured with a blood test called a full blood count (FBC). The figures below are a guide to the levels usually found in a healthy person.

These numbers can vary from hospital to hospital. Your doctor or nurse will tell you which levels they use. They also vary slightly between people from different ethnic backgrounds.

The numbers might look complicated when they are written down, but doctors and nurses often use them in a simple way. For example, you may hear them saying things like, ‘your haemoglobin is 140’ or ‘your neutrophils are 4’.

If you would like to know more you can always ask your medical team to explain in more detail.


 Type of cell  Levels found in a healthy person
 Red blood cells – measured in haemoglobin (Hb) levels 130-180g/l (men)
115-165g/l (women)
 Platelets 150-400 x 109/l 
 White blood cells (WBC) 4.0-11.0 x 109/l 
 Neutrophils 2.0-7.5 x 109/l 
 Lymphocytes 1.5-4.5 x 109/l 


Liver function tests (LFTs)

Blood tests called liver function tests (LFTs) check how well your liver is working. A sample of blood is taken and the level of different substances is measured.

Tumour markers

Some cancers produce chemicals that can be measured in the blood called tumour markers. These can also be raised in conditions other than cancer, so they are not always reliable.

Your specialist may use different tumour markers to help them make a diagnosis or to see how the cancer is responding to the treatment:

  • PSA (prostate specific antigen) to check for prostate cancer.
  • Human chorionic gonadotrophin (HCG) to check for germ cell tumours – a rare type of cancer that can start in the testicles or ovaries.
  • Alpha-fetoprotein (AFP) to check for some types of germ cell tumour and some types of primary liver cancer.
  • CA125 to check for ovarian cancer.
  • CA15-3 to check for breast cancer.
  • CA19-9 to check for cancer in the pancreas or bile ducts.
  • Carcinoembryonic antigen (CEA) to check for bowel cancer.
  • Chromogranin A (CgA) to check for neuroendocrine cancers – rare cancers affecting the neuroendocrine system that produces the body’s hormones.

Other blood tests

Blood tests can check for substances that may be associated with a particular type of cancer. These substances might include certain proteins or hormones.

There are also blood tests which look at the chromosomes, the structures which are made up of our genes.

Your doctor will be able to tell you more about which blood tests you might need. You can read more about specific blood tests in the information about your type of cancer.

Kidney function tests – urea and electrolytes (U+E)

These blood tests check how well your kidneys are working.