The FOB and FIT tests

The faecal occult blood (FOB) test and faecal immunochemical test (FIT) both check for hidden blood in your poo. These tests come as home screening kits. There are different screening programmes in the four countries of the UK.

Once you reach the bowel screening age for where you live, you will be sent a home screening kit. The main difference between the two tests is that you only need to send one sample of poo for the FIT test. The FOB test needs three samples to get a complete result.

It can take up to 2 weeks to get the results of your bowel screening test. There are three possible test results:

  • Normal – no blood has been found and you do not need more tests.
  • Abnormal – blood was found. Blood in your test result does not mean you have cancer, but you may need more tests.
  • Unclear – some blood was found, but not enough for an abnormal result. You may be asked to do the screening test again.

If you feel anxious when waiting for your results, it may help to talk to someone. You can choose whether to take part in bowel cancer screening.

What are the FOB and FIT tests?

The FOB and FIT tests can detect tiny amounts of blood in your poo.

Blood in your poo does not mean you have cancer, but bowel cancers and polyps sometimes bleed. There can be other causes for blood in poo. If your test finds blood, you will be offered another test to find the cause of the bleeding. This will usually be a test called a colonoscopy.

Using the test kits

You will get a home screening kit when you reach the age that bowel cancer screening starts in your country.

The main difference between FOB and FIT tests are the number of samples you need to take:

  • For the FOB test, you need to take three different poo samples, each on different days.
  • For the FIT test, you only need to take one sample.

You return the samples to the test centre in a pre-paid envelope. The test kit comes with a set of instructions. Before you take a sample, it is helpful to:

  • read through all the instructions
  • get everything you need ready
  • write any details on the test kit, for example the date.

If you have any questions about the sample collection, or have a disability that makes using the kit difficult, call your country’s screening helpline. If you need a new test kit, they can send you one. These are the helpline numbers:

  • In England, call 0800 707 6060, Monday to Friday, 9am to 5pm.
  • In Scotland, call 0800 0121 833, Monday to Friday, 8am to 5pm.
  • In Wales, call 0800 294 3370, Monday to Friday, 8am to 5pm.
  • In Northern Ireland, call 0800 015 2514, Monday to Friday, 9am to 5pm.

If you live in England, you have 14 days to return the test card after taking the first sample.

In the rest of the UK, you have 10 days to return the test card after taking the first sample. You will get a reminder after about 4 weeks if you do not return the test kit.

If you decide not to take part in the screening programme, you can choose not to respond. Or you can contact your country’s helpline to say you will not be sending your kit back.

I read it through and made sure I had everything prepared. It told you exactly what to do and how to set it up. I thought it was very straightforward.


Test results

Waiting for your results can be an anxious time. It may help to talk things over with a relative or close friend. Or talk to one of our cancer support specialists on 0808 808 00 00.

You should get a letter with the results of your home screening test within 2 weeks. Your GP will also get a letter.

With the FOB test, there are three possible test results:

  • normal
  • abnormal
  • unclear.

The FIT test gives only a normal or abnormal test result.

Normal result

Around 98 out of 100 people (about 98%) have a normal result. This means no blood was found.

2 years after your test, you will be sent another test kit if you are still within the age range.

If you have any symptoms before your next screening test, it is important to go to see your GP. Do not wait for your next test kit.

Symptoms of bowel cancer include:

  • an unexplained change in bowel habit, such as diarrhoea, constipation or both, that does not go away
  • bleeding from the back passage (rectum) or blood in your poo
  • looser poo or diarrhoea that lasts for 3 weeks or more
  • a feeling of not having emptied your bowel properly after going to the toilet
  • a pain or lump in your tummy or back passage
  • loss of weight or appetite
  • feeling more tired than usual for 2 to 3 weeks, with no obvious reason.

Abnormal result

About 2 in 100 people (around 2%) have an abnormal result.

If you have this result, it means blood was found in your test. Blood in your test result does not mean you have bowel cancer. Only about 1 in 10 people with an abnormal result (about 10%) have cancer.

Blood in poo can be caused by other conditions. Some people may have bleeding from small, non-cancerous growths in the bowel called polyps. Or it may be something less worrying, such as piles (haemorrhoids).

If you have an abnormal result, you will be offered an assessment and probably a bowel test called a colonoscopy.

Unclear result

A small number of people may have an unclear result. This means there was some blood detected, but not enough to give an abnormal result.

Having an unclear result does not mean you have bowel cancer. It just means you need to do a second test to check for blood in your poo. You will be sent another home screening kit. Most people who do the second test get a normal result. If the result of your second test is normal, you may be sent another kit to confirm the result.

If the result of the second test is unclear or abnormal, you will usually be offered a colonoscopy.

Sometimes you may be asked to repeat the test. This may be because of the following reasons:

  • A technical failure. This means there was a problem when your samples were tested in the laboratory. If this happens, you will be sent a letter and another test kit to collect more samples.
  • A spoilt kit. This means the test kit cannot be tested in the laboratory, because it has not been used properly or has been damaged. If this happens, you will be sent a letter and another test kit to try again.

Back to Bowel screening

Bowel scope screening

This test looks at the lower part of your large bowel. It can help find cancer at an early stage.


A colonoscopy is a test that looks at the inside of the large bowel.

Virtual colonoscopy

This test is also called a CT colonography. It uses a CT scanner to build a picture of the bowel.

Be bowel aware

It is good to be aware of the symptoms of bowel cancer and ways to reduce your risk.