Medical Imaging

Intravenous Contrast

Some scans will require oral or intravenous contrast. Intravenous contrast is a clear fluid which highlights the blood vessels and therefore visualise the flow of blood to various part of the body. This fluid is generally injected into a vein in the arm. You may be required to consume 3x drinks of contrast before the examination commences. The contrast is injected to highlight the blood vessels allowing us to see the blood flow to the organs and vessels within the body.


If intravenous contrast is required for your examination then follow the instructions below:

  • You may be required to fast prior to your appointment time so ensure you check with the staff when making an appointment.
  • Take all medications with sips of water (unless otherwise instructed), including blood pressure medications.
  • A recent blood test will need to be completed to assess the function of your kidneys prior to your appointment. If your blood test was taken outside the hospital then you will need to obtain a copy of the results and bring it to your examination.

If you require an interpreter, please inform the booking clerk at the time of booking.

  During the Procedure

The CT examination bed will move in and out of the CT scanner multiple times as the image is set up ready for the injection of contrast.

There are a few mild side effects to expect during the injection of contrast. The most common being:

  • A sensation of heat (hot flush),
  • An unusual taste (metallic) in your mouth and
  • A sensation in your bladder (of going to the toilet)

These sensations are considered normal when the IV contrast is being injected and do not last long after the injection.

  After the Procedure

If you have had an examination with intravenous contrast then it is important to help flush the contrast out of your body by drinking plenty of fluids after the scan.

If you are currently taking oral hypoglycaemic such as Metformin, Diabex or Janumet for diabetes and have had the injection of contrast then it is advised to stop this medication for 48hrs after your scan. This is to prevent a build up of this medication in your system. If you are unsure whether this applies to you then please brings a list of medications to your appointment so we can advise you.

  Contrast Extravasation

In rare occasions the cannula (needle) that is inserted into your vein for the examination dislodges from the vein during the injection of contrast. This results in the contrast being injected into the surrounding tissues instead of the vein. This causes redness, swelling and pain at the insertion site.

Post care instructions to help with the swelling and pain involve: 

R = rest
I = ice or heat
C = compression
E = elevate

If you experience numbness or tingling, loss of sensation seek medical advice or GP 


The main risks involved with any CT scan are associated with the contrast injection. Patient safety is our first priority and for this reason we use the safest non-ionic contrast available.

If you have an allergy to iodine then please inform the receptionist when booking an appointment. This will need to be discussed with the doctor to advise the best option to deal with your allergy. In some cases a course of medication may be required prior to your examination to alleviate any symptoms of an allergic reaction. Your scan could be performed without the use of contrast or the doctor might suggest a different type of examination.

Contrast can affect patients who are identified as having renal impairment. Contrast can cause further kidney damage and may cause the kidneys to stop working properly. This is why it is extremely important for the staff to have access to your recent blood results prior to having the injection.




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Page last updated: 19 November, 2014