The endoscopist (doctor or nurse carrying out the test) will explain what is going to happen, and will answer any questions you have. S/he will ask you to sign a consent form to say that you agree to have the test done. S/he will also complete a health checklist with you.

You may need to change into a hospital gown. Alternatively you can wear loose, comfortable clothing.

You will go to a treatment room and lie on a couch, on your left hand side.

A sedative will be injected into a vein to make sure you don't feel too much discomfort. You may be sleepy.

When you are ready, the doctor or nurse will pass the colonoscope through the rectum and into the large bowel. Some air is put into the bowel. This expands the lining slightly, to give a clear view of the inside of the bowel. The pressure of the air may give you stomach pains or cramps.

The doctor or nurse may also take some samples of tissue (biopsies) from the lining of the bowel. These will go to the laboratory later.

Once your doctor or nurse has finished the examination s/he will gently remove the colonoscope, and the test is over.

Most tests take around 30 minutes, but some last a bit longer.