A computed tomography scan (CT scan) is a commonly used medical imaging exam to view different parts of the body. Whether it is being done to assess pain, monitor a condition, or support a diagnosis, it is normal to have questions about how to prepare for a CT scan.

This article covers the main information to help you better understand how to prepare for a CT scan, especially if you have an upcoming exam at a medical imaging clinic in Montreal.

Why is preparation sometimes necessary for a CT scan?

Preparation for a CT scan may vary depending on:

  • the area of the body being examined (abdomen, chest, brain, etc.)
  • whether or not contrast material will be used
  • your health condition

Its purpose is to:

  • optimize image quality
  • make certain structures easier to visualize
  • ensure the exam is performed safely

👉 At Radimed, information and instructions tailored to your situation are provided when you book your appointment, based on the exam you are scheduled to have.

How to prepare for a CT scan in Montreal

Before your medical imaging appointment, you may be given certain instructions to help ensure the exam goes smoothly and the images are of high quality.

Do you need to fast before a CT scan?

In some cases, you may be asked to avoid eating or drinking for about 3 hours before the exam, especially:

  • if contrast material will be used
  • for certain abdominal or pelvic exams

In other situations, no specific dietary restrictions are required.

Is a blood test required?

In some situations, a recent blood test may be requested before a CT scan.

Why?

It is used to assess kidney function (estimated glomerular filtration rate), particularly if contrast material is planned.

In which cases?

A blood test may be requested if you:

  • are over 60 years old
  • have diabetes
  • have a history of kidney disease
  • take certain medications

👉 Results generally need to be recent, according to current recommendations.

Contrast material: specific preparation

Some CT scans are performed with iodinated contrast material, given intravenously or sometimes orally.

This material helps improve visualization of:

  • organs
  • blood vessels
  • certain conditions

Before the exam, certain checks may be carried out, particularly regarding:

  • allergies
  • kidney function
  • the use of certain medications
  • pregnancy or the possibility of pregnancy

In some cases, you may also be asked to drink a contrast liquid before the exam.

Medications: do they need to be adjusted?

In most cases, your medications can be taken as usual.

If you are asked to change or temporarily stop a medication, it is recommended that you confirm this instruction with the doctor who prescribed it.

On the day of the exam: details not to forget

Documents to bring

  • valid health insurance card
  • medical prescription
  • previous imaging results (if available)
  • blood test results (if requested)

What to wear

  • choose comfortable clothing
  • avoid metal objects (jewelry, watches, accessories)

👉 You may be asked to wear a gown to reduce interference with the images and help the exam proceed smoothly.

Arrive early

It is generally recommended that you arrive 15 to 30 minutes before your appointment in order to:

  • complete a questionnaire
  • confirm your medical information
  • ask your questions

How the exam works (helpful overview)

Before beginning, the medical imaging technologist:

  • reviews your history and allergies
  • explains how the exam will proceed

If contrast material is required:

  • a small catheter may be inserted into a vein in your forearm
  • it is removed at the end of the exam

During the exam:

  • you will usually lie on your back
  • the table moves through the scanner while images are taken

Possible sensations

When contrast material is injected, you may experience certain sensations:

  • a feeling of warmth
  • a metallic taste in your mouth
  • a temporary sensation of needing to urinate

These effects are usually short-lived and go away quickly.

Length of the exam

A CT scan usually takes between 15 and 30 minutes, depending on the exam.

After the exam: are there any instructions?

After the exam:

  • it is often recommended to stay well hydrated, preferably by drinking water, as this may help flush out the contrast material.

You can generally resume your usual activities.

In summary: key preparation points

  • You may be asked to avoid eating or drinking before the exam
  • A blood test may be required in some cases
  • The contrast material requires certain precautions
  • Your medications should be reviewed if needed
  • Practical details (documents, clothing, arrival time) make your experience easier

Guided preparation at Radimed

At Radimed, every patient receives preparation instructions when booking their appointment, to ensure that the exam takes place under optimal conditions.

To better understand what to expect on the day of your appointment, you can read our article on the CT scan procedure.

To learn more about our services, visit our page dedicated to CT scans at Radimed in Montreal.

Sources

  • INESSS
  • Health Canada
  • OTIMROEPMQ