What to Expect During a CT Scan

A CT (computed tomography) scan, also called a CAT (computed axial tomography) scan, is a diagnostic exam used to detect tumors, determine the stage and location of a cancer, and find out about the effectiveness of cancer treatment. The CT scan may also be used to guide a doctor who is performing a biopsy (the removal of a small amount of tissue for examination).

The CT scan obtains multiple cross-sectional images of your body by using special x-rays and computer enhancement, creating an image many times more sensitive than the image from a simple x-ray. The visit will generally last 1 to 1 ½ hours, although the scanning itself takes only 10 to 15 minutes. When the scan is finished, you may be asked to remain on the exam table while a radiologist reviews the images to determine if additional images are needed.

Preparing for Your CT Scan

  • Tell the doctor if you previously had an allergic reaction to intravenous (IV) dye or any other allergies, especially iodine.
  • When your doctor schedules a CT scan, let him or her know if you have diabetes (sugar in the blood) and take a drug called Glucophage® (metformin). You may be asked not to take this medication the day of your CT scan, and 2 days following the scan. Check with your doctor for your specific instructions.
  • Tell your doctor/nurse about all your medications, including over-the-counter products, vitamins, and herbal supplements.
  • Check with your doctor/nurse if you should take your regular medications that day.
  • Women  please tell your doctor if you may be pregnant or are breast-feeding.
  • Do not eat anything for 6 hours before your scan.
  • Do not drink anything for 2 hours before your scan.


The day of your CT scan

  • If you have been instructed to take medications on the day of your scan, you may take them with a small sip of water.
  • Wear loose, comfortable clothing to your appointment. When you arrive for your CT scan, you may need to change into a gown.
  • You will be asked to remove any item that contains metal (including jewelry, eyeglasses, dentures and hairpins) because metal objects may affect the CT images. You may also be asked to remove hearing aids and removable dental work.
  • Tell the technologist if you have: – any allergies to IV dye, iodine – asthma – multiple myeloma– diabetes– any disorder of the heart, kidneys or thyroid gland
  • You may receive a contrast agent before the scan, which may be a drink, an intravenous (IV) injection, or both. The contrast helps create a clearer picture of the parts of the body being scanned.
  • Intravenous contrast may cause you to feel hot or get a metallic taste in your mouth; both sensations should disappear after a few minutes. If you experience a more serious reaction, tell the technologist immediately.
  • If you have a liquid contrast drink, you will need to wait up to 1 hour before your scan can begin.
  • A technologist will help position you on the table and then monitor the procedure from an adjoining control room. You can communicate through an intercom system.The CT scan resembles a large donut. The exam table will slide back and forth through the large hole in the center of the machine as the scanner rotates around you. You will hear whirring or clicking sounds from the machine; some machines are noisier than others.
  • CT scans are not painful. You will need to lie still for the entire scan, which may become uncomfortable. You may be asked to hold your breath during part of the scan because the motion created by breathing can blur the images. The exam table may be raised, lowered, or tilted to create the correct angle for the x-rays. Ask the technologist performing the scan to tell you when the table will move.

After the Procedure

  • You can expect to resume your normal activities immediately after your CT scan, including driving.
  • If you received a contrast agent for the scan, you may be asked to drink a lot of water to help flush it out of your body.