About Children's Cancer

Blood tests

Blood tests are important to help diagnose many types of cancer. Blood tests are also used to check for general health and organ function.

Some cancers produce substances (called cancer markers or tumour markers) that can be detected in the blood. If the blood tests show tumour markers, your child will have other tests to determine if they have cancer.

To do a blood test, the doctor will insert a small needle in your child’s arm (usually in a vein on the inside of their elbow). The doctor will collect a small amount of blood to be tested in a laboratory. The blood test shouldn’t be painful but might be cause a little discomfort to your child initially.

Your child may have several blood tests at different times. If your child does have cancer, they will need to have more blood tests during and after treatment.

Blood samples need to be sent to a special laboratory to check them. It can sometimes be a few days before you find out the results.

The most common blood tests are a full blood count and blood chemistry.

You can find links to further support and advice at our Find support and more information page.


Full blood count (FBC)

A full blood count (FBC) is sometimes called a complete blood count (CBC). This test measures the numbers of different cell types in the blood, including;

  • white blood cells
  • red blood cells
  • platelets.

Cell counts that are too high or too low can indicate cancer.

Blood chemistry

Blood chemistry tests measure the levels of different substances in your child’s body, including:

  • minerals
  • enzymes
  • hormones
  • waste products
  • tumour markers (sometimes called biomarkers).

Doctors use these tests to check whether organs are functioning properly. This could include the kidneys, liver, lungs and heart.