CT scans and other x-rays are strictly monitored and controlled to make sure they use the least amount of radiation. The risk associated with any individual scan is very low. The risk increases as numerous additional studies are performed.
In some cases, a CT scan may still be done if the benefits greatly outweigh the risks. For example, it can be more risky not to have the exam, especially if your health care provider thinks you might have cancer.
The most common type of contrast given into a vein contains iodine. If a person with an iodine allergy is given this type of contrast, nausea, sneezing, vomiting, itching, or hives may occur.
If you absolutely must be given such contrast, your doctor may choose to treat you with antihistamines (such as Benadryl) or steroids before the test.
The kidneys help filter the iodine out of the body. If you have kidney disease or diabetes, you should be closely monitored for kidney problems after this test. If you have diabetes or have kidney disease, talk to your health care provider before the test about your risks.
Before receiving the contrast, tell your health care provider if you take the diabetes medication metformin (Glucophage) because you may need to take extra precautions and stop the medication for 48 hours after the test.
In rare cases, the dye can cause a life-threatening allergic response called anaphylaxis. If you have any trouble breathing during the test, you should tell the scanner operator right away. Scanners come with an intercom and speakers, so the operator can hear you at all times.