Blood tests for neuroendocrine tumours (NETs)

Blood tests can help to diagnose some types of neuroendocrine tumours. You might also have one to check your general health.

Why you might have a blood test

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 can look 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.

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 of having a blood test

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. 

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 . 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.

Hormone levels

Blood tests can show if there is a higher than normal level of hormones in the blood.

If your doctor suspects a neuroendocrine tumour they might look at the levels of:

• gastrin

• glucagon

• insulin

• serotonin

• vasoactive intestinal peptide

Chromogranin (CgA test)

The chromogranin A (CgA) test measures the amount of CgA in the blood. CgA is a protein that many neuroendocrine cells produce. But CgA can also be raised for other reasons that are not related to cancer. So, the test is not used on its own to diagnose a NET.

You might have a blood test to check for the level of the protein chromogranin B (CgB) in the blood. This is less common than having a CgA test.

Long fasting test for insulinoma

You might have a long fasting test to help your doctor to diagnose a type of pancreatic NET called insulinoma. It is to check if your blood sugar levels go down if you don’t eat. 

Your nurse might put a small tube (cannula) into your vein. Your nurse takes regular blood samples to check your blood sugar. You can drink water but not eat or drink anything else for up to 72 hours.

You stay in hospital for this test. This is so your nurses can give you something to eat or drink if your blood sugar gets very low.

Other tests

Most people have several tests to diagnose a neuroendocrine cancer. You can find out what other tests you might have in your specific neuroendocrine cancer section.

This page is due for review. We will update this as soon as possible.