CT scan

A CT scan uses x-rays to build a detailed picture of the inside of the body. You may be given either a drink or injection of dye.

What is a CT scan?

A CT scan makes a detailed picture of the inside of the body. The picture is built up using x-rays taken by the CT scanner. The scan uses radiation, but this is very unlikely to harm you. It will not harm anyone you come into contact with.

CT scan
Image: CT scan


Before a CT scan

You will get an appointment letter telling you whether you need to do anything before the scan. You may be asked not to eat or drink for a few hours before the scan. This depends on the part of the body being scanned. If this is a problem for you, call the number on your appointment letter.

You should tell the radiographer if you are pregnant or think you could be.

When you arrive at the hospital, you may be asked to put on a hospital gown. You may also be asked to remove any jewellery or objects containing metal from your body. This includes:

  • piercings
  • hair clips
  • zips
  • your bra.

This is because the metal in these objects can affect the picture made by the scanner.

You may have a drink or injection of a dye. This is called a contrast. It helps show certain areas of the body more clearly. The contrast may make you feel hot all over for a few minutes. Tell your doctor if you are allergic to iodine or have asthma. This is because you could have a more serious reaction to the injection.

Having a CT scan

You have the scan in the x-ray department at the hospital. The person who works the scanner is called a radiographer. The scan takes 5 to 10 minutes, but you may be in the department for longer. The scanner looks like a large, thick ring. You lie still on a narrow bed which moves slowly backwards and forwards through the ring. The scan is painless.

You can usually go home after the scan. If you had a contrast, the radiographer may suggest you drink plenty of water for the rest of the day. This will help flush it out.

Booklets and resources

Types of CT scan

There are some specialised types of CT scan. These may be used to help diagnose some types of cancer. They may also be used to check how well treatment is working. These include the following:

  • CT urogram

    A CT urogram looks in more detail at the bladder, kidneys and ureters (tubes that drain urine from the kidneys to bladder).

  • Virtual colonoscopy (CT colonography)

    A virtual colonoscopy looks at the bowel in more detail.

You can read more about specialised types of CT scan in our information about different cancer types.

Date reviewed

Reviewed: 24 January 2022
Next review: 24 July 2024
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