CT Scan or (Computed Tomography)  Frequently Asked Questions

Should I Be Worried About The Radiation From My Scan?

The short answer to the question is.... a little. CT studies require ionizing radiation to produce images. Any time you are exposed to this type of energy cell break down will occur and your chances of getting a radiation induced condition, like cancer, is increased. In theory any amount of ionizing radiation can alter cells and cause them to turn cancerous. In reality this is highly debated. Most dose relationship studies have focused on exposure to large amount of radiation. The chances of actually getting cancer or some other radiation induced process from a couple CTs or XRay studies is extremely improbable.

The patients at greatest risk are those who have quarterly, biannual, or annual CT studies to follow conditions like the progression of cancer (ironically), bowel disease, or other conditions which are well seen in CT. Don't worry about it so much if you need a diagnosis and CT is your best option. In many disease processes early detection far outweighs the possible effects of radiation based studies.

Additionally, many newer CT scanners utilize what is referred to as "Care Dose". This new feature automatically selects the minimum amount of radiation necessary to get a quality scan based on patient demographics and other information once the scan starts. 

Any radiation based study has to be evaluated in a risk benefit analysis. This is best done with your ordering doctor. If he or she does not feel comfortable discussing this call a radiologist at your local imaging facility. Most of them are extremely knowledgeable about radiation safety and wouldn't mind taking a minute to ease your fears.

How Should I Prepare For My CT Scan?

Wear clothing with as little metal as possible and leave removable metal items like jewelry, pocket change, etc at home. This is true across the board for most CT studies. Other than that there is no standard prep. CT studies of the abdomen and pelvis frequently require oral contrast and require the patient to arrive 1-2 hours before the start time to drink. Some CT studies of the heart may require beta blockers to be taken just before the study. CT virtual colonoscopy studies require the patient to have nothing to eat or drink but clear liquids for 24 hours prior.

Some CT studies of the heart may require beta blockers to be taken just before the study. CT virtual colonoscopy studies require the patient to have nothing to eat or drink but clear liquids for 24 hours prior.

Many studies require an intravenous contrast injection (through an IV). If this is the case most institutions require that the patient have nothing to eat or drink 2- 4 hours prior to the study. 

Is The CT Contrast Safe?

CT contrast is an iodine based dye that is intravenously injected into the body. If your doctor requests the study to be performed with contrast the technologist will give you a small IV and inject it just prior to or during the scan while you are on the table. The contrast is generally regarded as a very safe and reactions rare but it is a drug and, just like any other drug you've ever taken, you could be allergic to it.

There are some patients who are at a higher risk of having an allergic reaction to the contrast. These include: asthmatics, patients who have severe cardiovascular disease, and patients who have other sever allergies. If you have concerns speak with your doctor or consider calling the radiologist at the site you plan on having your study at. They may consider other imaging options or even "pre- medicate" you to prevent an allergic reaction with steroids, diphenhydramine (Benadyl), or a combination of both. Due to adverse effects of steroids you and your doctor would have to talk about the risks and benefits of either choice.


Another group of patients who need to be screened before a CT contrast injection are those who have compromised renal function. The contrast can cause severe damage to patients whose kidneys are not working well in the first place. Each institution has their own policies but typically those great than 60, who have diabetes, who've had a recent spike in blood pressure or uncontrolled hypertension, who have or have had a history of kidney disease, or those on dialysis will need blood work to check their creatinine level before an injection. High creatinine levels indicate poor kidney function and may prohibit a patient from having contrast. Your doctor should provide you with a script for blood work when they order the CT study. That way your results can be sent to the imaging center before you arrive for your scan. You don't want to waste your time if you can't get scanned. Many centers now have their own creatinine machines to test your blood on site. It couldn't hurt to call the center you plan on having your study at to see if they provide this service. It may save you a trip!

How Long Is A CT Scan?

CT scans are normally extremely quick. You can expect the scan itself to take between 5-10 minutes. Unfortunately if you need to drink oral contrast before your study you may have to arrive onsite 60- 120 minutes beforehand to give the contrast time to make it's way through your bowel before the scan. Insiders tip... many centers will let you pick up the oral contrast beforehand. This way you can run errands for an hour or so an not have to be in a crowded waiting room!

Can I Have A CT Scan If I Am Pregnant?

Ideally no. Although the damage to an unborn child is difficult to measure fetal abnormalities, damage, and brain malformation  are legitimate risks; this increases with the amount of radiation exposure. There are other imaging modalities that do not utilize radiation like MRI or ultrasound that should be considered before exposing a pregnant mother.


In some rare cases, typically in an emergency situation, CT may be the only option to properly diagnose a life threatening condition in the mother. If If the mother is unconscious this decision may be made by whomever has power of attorney or emergency physicians.


If you do happen to have a CT scan while pregnant your baby will most likely be fine. With this being said there is a risk and this should be discussed in conversation involving your OB and the Radiologist. 

Can I Take My Medications Before & After The CT Scan?

For a non IV contrast CT study all medication is fine to take as usual. If IV contrast is going to be administered all medication is fine to take as usual with the exception of your diabetes medicine (not including insulin). It all goes back to the kidneys again. If your kidneys are not functioning well and you take some diabetes medications like glucophage or metformin after your scan you can put your kidneys in a state of acidosis; this could cause some serious damage. If you are having a CT study with contrast and taking drugs like these consult with your ordering doctor beforehand. If you have compromised renal function in the first place the doctor may request blood work to check your kidney function before you start your diabetes medicine again. 


Consider that those at risk of kidney disease are aggressively screened by radiology centers before administration of CT contrast. These policies and procedures typically make this a mute issue but many centers recommend ceasing your diabetes medication for 48 hours after your exam to be on the safe side. 

Am I Radioactive After The CT Scan?

No, not in the least!