CT scanning is a minimal-risk procedure. The amount of X-ray radiation that you are exposed to is minimal and well within the safe range. If contrast material is to be administered you will be asked several questions in order to ensure that you will not be harmed by the dye.
You must report any allergies, especially to shellfish or to iodine-containing compounds (most contrast agents are iodine-based). Most people do not have an allergy to contrast material and it is likely that you will tolerate the dye without any difficulties. Some people, however, develop an allergic reaction which may include itching, nausea, vomiting, a rash and respiratory difficulties. Immediately notify your CT technologist should you experience any of these symptoms. In rare cases an anaphylactic reaction may occur. This is a severe reaction and requires immediate medical attention.
Patients who are dehydrated or suffer from diabetes mellitus are at an increased risk for kidney damage. Likewise patients with underlying kidney disease risk further damage to their kidneys. If you have any of these conditions you need to inform your physician.
If you are pregnant or suspect that you may be pregnant, you must inform your physician, the radiologist and/or the CT technician. X-rays may cause harm to the fetus especially during the first three months of the pregnancy. Sometimes a shielding device may be used in order to minimize the amount of exposure if the CT has to be performed despite your being pregnant.