What are the risks of CT scans?
A CT scan is a very low-risk procedure. However, during a CT scan you're briefly exposed to much more radiation than during a normal X-ray. Radiation exposure potentially increases your risk of developing cancer, but doctors and other scientists believe that CT scans provide enough valuable information to outweigh their potential risks.
The most common problem arising from a CT scan is a reaction to the intravenous contrast material some CT scans require. Most reactions are mild and result in hives or itchiness. In rare instances, an allergic reaction can be serious and potentially life-threatening. Some have put the chance of a fatal reaction to the contrast at about 1 in 100,000. Make sure to tell your doctor if you've ever had a prior reaction to contrast material during medical tests.
Be sure to inform your doctor if you're pregnant. He or she may recommend another type of exam, such as ultrasound or magnetic resonance imaging (MRI), to avoid the risk of exposing your fetus to the radiation.
A person who is very large may not fit into the opening of a conventional CT scanner or may be over the weight limit for the moving table which is usually about 450 pounds.
There is a slight risk that the CT scan can interfere with implanted or external medical devices.
Your risk of having a problem due to IV contrast may increase if you have a history of heart disease, asthma, diabetes, kidney disease or thyroid disorders. Nursing mothers should wait for 24 hours after contrast material injection before resuming breast-feeding. Because children are more sensitive to radiation, they should have a CT study only if it is essential for making a diagnosis and many doctors recommend not doing repeated CT studies unless absolutely necessary.
Reactions to the contrast are almost always immediate, so it is very rare to have a reaction after you leave the facility. However, if you think you are having a delayed reaction to the contrast, call the facility where you had the exam. Symptoms can include itching and difficulty breathing or swallowing. If contrast has leaked under the skin, you may see or feel increased redness, swelling, or pain. You will often be asked to come back the next day so your skin can be checked.