Blood tests for acute lymphoblastic leukaemia (ALL)

Blood tests can:

  • check your general health, including how well your liver and kidneys are working
  • check numbers of blood cells
  • help diagnose cancer and other conditions

Your blood sample is sent to the laboratory. A specialist doctor called a pathologist looks at your sample under a microscope. They can see the different types of cells and can count the different blood cells. They can also test for different kinds of chemicals and proteins in the blood.

Preparing for your blood tests

You can eat and drink normally before most blood tests. For fasting blood tests you need to stop eating and drinking beforehand. Your doctor will tell you for how long.

What happens?

You sit or lie down to have the test.

A doctor, nurse or phlebotomist (person specialised in taking blood) chooses the best vein to use. This is usually from your arm or hand. Let them know if you are afraid of needles, get unwell with the sight of blood or are allergic to plasters or latex. 

They put a tight band (tourniquet) around your arm above the area where they take the sample. You may need to clench your fist to make it easier to find a vein.

They clean your skin and then put a small needle into your vein. Next, they attach a small bottle or syringe to the needle to draw out some blood. They might fill several small bottles.

Once they have all the samples, they release the band around your arm. They then take the needle out and put pressure on the area with a cotton wool ball or small piece of gauze for a few minutes. This helps to stop bleeding and bruising.

Look away when they’re taking the blood if you prefer. Tell your doctor, nurse or phlebotomist if you feel unwell.

Photograph of a blood test

Getting your results

Ask the phlebotomist, doctor or nurse when and how you will get your results. Some results might be available very quickly, such as a full blood count and kidney and liver function tests. Other tests might take several weeks.

Possible risks

Blood sampling (phlebotomy) is a safe test. There is a possibility of:

  • bleeding and bruising - pressing hard when the needle is removed can help to stop it
  • pain - this is normally mild and can last for a few minutes
  • swelling (oedema) - ask your nurse, doctor or phlebotomist to avoid an arm that is swollen or has a risk of swelling
  • feeling faint or fainting - tell the person doing your blood test if you're feeling lightheaded or dizzy at any time
  • infection - this is very rare

Types of blood tests

Full blood count

A full blood count (FBC) measures the number of red cells, white cells and platelets in your blood.

  • Red cells carry oxygen around our bodies. Haemoglobin is the part of the cell that carries oxygen. If you have a low red cell count, your doctor might say you’re anaemic (pronounced a-nee-mic). This can make you feel tired, short of breath and dizzy.
  • White cells fight infections. There are several different types of white cells, including neutrophils and lymphocytes.
  • Platelets help clot the blood, for example after a cut. Symptoms of a low platelet count include abnormal bleeding, such as bleeding gums and nosebleeds.

There is a range of normal for blood counts. The range of figures quoted as normal varies slightly between laboratories and also differs between men and women. 

Diagram of table showing the normal values of men and women

Urea and electrolytes

These blood tests show how well your kidneys are working. Waste chemicals called urea and creatinine are produced by the body. Our kidneys remove them from our blood and get rid of them in our urine.

Electrolytes are substances such as sodium, potassium, chloride and bicarbonate.

Liver function tests (LFTs)

Liver function tests (LFTs) check how well your liver is working. LFTs look for levels of enzymes and proteins made by the liver or which are cleared by the liver. They include:

  • alanine aminotransferase (ALT)
  • aspartate aminotransferase (AST)
  • alkaline phosphatase (ALP)
  • gamma-glutamyl transferase (Gamma GT)

They might be raised if you have a blockage in your liver or bile duct, or if you drink a lot of alcohol.

LFTs also look at the amount of bilirubin in the blood. This is a chemical in bile Open a glossary item. Bilirubin can be raised if you have a problem with your liver or gallbladder. Bilirubin can cause yellowing of your skin and eyes (jaundice). 

LFTs also measure albumin. This is a protein in the blood that can be low when you have some types of cancer. You can also have low albumin if you’ve been eating small amounts and are malnourished.


This is an important test to tell your doctor what type of leukaemia you have. For example, if it’s acute lymphoblastic leukaemia (ALL) or acute myeloid leukaemia (AML). It also gives further information about the sub type of ALL you have such as B cell or T cell ALL. This test also tells your doctor how well your treatment is working. This test is carried out on your blood or bone marrow cells.

Tests on your leukaemia cells

Other laboratory tests may be carried out on the blood or bone marrow cells you've given. Your haematologist will order these tests to look for changes (abnormalities):

  • on the surface of your leukaemia cells
  • in the genes and chromosomes of your leukaemia cells

These are also sometimes called cytogenetic, molecular analysis or polymerase chain reaction (PCR) tests.


This is an important test to help find out what:

  • type of leukaemia you have such as if you have ALL or another type of leukaemia such as acute myeloid leukaemia (AML)
  • subtype of ALL you have such as B cell or T cell ALL

It can also help find out if your leukaemia has gone away after treatment.

Acute lymphoblastic leukaemia cells look very different on their surface from all other normal cells in the body. These can be easily picked up with another method called flow cytometry. This test helps tell your doctor how well your treatment is working. This test can be carried out on your blood if leukaemia cells are present but it is normally done on bone marrow samples.

FISH (fluorescence in situ hybridisation)

FISH is a test that looks for chromosome changes in cells. It can help your doctor to work out which treatment you need. Philadelphia positive ALL is the main subtype of ALL that is picked up by this method. But there are also many other chromosome changes that are important in helping your doctor understand more about your leukaemia.

Philadelphia chromosome

Some people with ALL have a change in the chromosomes of their leukaemia cells called the Philadelphia chromosome. This is called Philadelphia positive ALL. The name came about as it was first picked up in a laboratory in Philadelphia many years ago. This is when a gene called the ABL1 gene on chromosome 9 breaks off and sticks to a gene called the BCR gene on chromosome 22. It produces a new gene called BCR-ABL1. This gene causes the cell to make too much of a protein called tyrosine kinase. This protein encourages leukaemia cells to grow and multiply.

Watch this 2 minute video to explain what Philadelphia positive leukaemia is. 

Polymerase chain reaction (PCR)

PCR stands for polymerase chain reaction and is a test to pick up changes in genes and chromosomes to help diagnose cancer. It helps your doctor work out the treatment you need. In leukaemia your doctor can also use it to monitor how well your cancer treatment is working.

Other genetic tests:

Newer types of genetic testing are becoming more routine. Doctors are using these to understand more about the gene changes that happen in leukaemia. These tests are done at specialist laboratories that have been set up around the UK. The are called genomic laboratory hubs. 

You can find out more about genomics and these specialist laboratories on the NHS website. 

Tests to check for infections

ALL and its treatment can weaken your immune system. This is because it stops your bone marrow from making blood cells that help fight infection. This then increases your risk of getting an infection.

You’ll have blood tests to check if you have had or have specific viruses before you start treatment. 

This is to help your doctor understand your risk of developing these viruses during treatment or the risk of them flaring up.

Your doctor usually tests for:

  • human immunodeficiency virus (HIV)
  • hepatitis B virus (HBV)
  • hepatitis C virus (HCV)
  • herpes simplex virus (HSV)
  • Epstein-Barr virus (EBV)
  • Cytomegalovirus (CMV)
Last reviewed: 
21 May 2020
Next review due: 
21 May 2024
  • Oxford handbook of clinical medicine (10th edition)
    M Longmore, IB Wilkinson, A Baldwin and E Wallin
    Oxford University Press, 2017

  • Acute lymphoblastic leukaemia in adult patients: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow up
    D Hoezler and others
    Annals of Oncology, 2016. Volume 27, Supplement 5, Pages 69-82

  • The Royal Marsden Manuel of Clinical Nursing Procedures, Professional Edition (10th Edition)
    S Lister, J Hofland and H Grafton
    Wiley Blackwell, June 2020

  • Fluorescence In situ Hybridization: Cell-Based Genetic Diagnostic and Research Applications
    C Cui and others
    Frontiers in Cell and Developmental Biology, 2016. Vol 4, 89

  • BMJ Best Practice Acute lymphocytic leukaemia
    BMJ Publishing Group Ltd, last updated March 2021

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact with details of the particular issue you are interested in if you need additional references for this information.

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