CT scan (CAT scan)

CT scan

This is a type of X-ray that gives a very accurate picture of the location and size of any tumours. It takes X-rays from different angles to give a detailed 3D picture of the tissues inside your body.

Before the test

For some CT scans you may be asked to fast (not eat) for 4 hours beforehand. For others you may be given a special drink or injection which helps show up parts of your body on the scan. This is a kind of dye called a contrast medium. Let the radiographer know if you’re allergic to iodine or have asthma.

During the test

You lie on a table that passes through a large doughnut-shaped machine. You will have to lie as still as possible.
The table will move forwards and backwards through scanner until all the pictures are taken.
You will be on your own in the room but the radiographer can see you and hear you and will be able to talk to you through an intercom. If you need anything you can talk to the radiographer or just raise your hand, or you may have a buzzer to press.

Does it hurt?

No, but it can be a bit uncomfortable because you have to lie very still. Some people feel claustrophobic during the scan. Tell the radiographer if you’re worried about this before the test or if you feel uncomfortable during it. The injection can make you feel hot all over for a few minutes.

How long does it take?

The scan itself usually takes about 10-30 minutes. You may have to wait an hour before having the test if you are having the contrast medium (dye).

After the test

Most people can go straight home after the test.

Are there any side-effects or risks?

Allergic reaction

Some people are allergic to the contrast medium (dye). If you feel weak, sweaty, breathless or unwell in any way tell your radiographer immediately.


Being exposed to radiation slightly increases your risk of cancer in the future. Normally pregnant women only have a CT in an emergency situation. Tell the radiographer if you’re pregnant or there’s a chance you might be.

CT scan (CAT scan) video

Cancer Research UK has a very helpful video on this.

For more information

Icon: Phone


1800 200 700

Icon: Email