The Dangers of CT Scans and X-rays

A CT scan can lead to a diagnosis of your symptoms, but can it also do more harm than good? Learn about common medical imaging tests and your risks of radiation exposure.

Sanaz Majd, MD
5-minute read
Episode #127

Are There Any Good Studies on This Topic?

I should add that there is no good research that shows a direct cause-and-effect relationship between cancer and radiation exposure from tests, partly because it’s not very ethical to perform research on patients by giving them radiation to simply “see what happens.” Also, patients would have to be followed over many decades to see if something were to develop – that would take a lot of time. But most medical communities agree that there is a real risk. That’s why radiation exposure through imaging tests is a potentially big issue.

“Doctor, all I want is a full body scan to tell me if I have ‘anything bad’ going on?”

Did you know that one abdominal CT scan that takes just a few minutes is equal to receiving about 500 x-rays? And that’s just the abdomen. CT scans carry the greatest risk from ionizing radiation exposure. If your doctor suggests getting a CT scan, make sure you find out:

  • What they are looking for exactly? Is it a pocket of pus/abscess, appendicitis, a tumor, etc.

  • How likely is it that a CT will actually show what they are looking for? Sometimes CTs aren’t the best at showing some anatomical structures, such as gall bladder stones.

  • How important is it to find what they are looking for? If you’ve had diverticulitis before, and your symptoms are exactly the same and mild this time around, is it necessary to do another CT scan?

Always be sure to discuss these questions with your doctor in advance.

You may be wondering about ultrasounds and MRIs? They actually don’t use ionizing radiation. MRIs use magnetic and radio waves, and ultrasounds use sound waves. And routine mammograms? Like I mentioned, a single x-ray, even if you get yearly ones starting at age 40, doesn’t amount to 500 by the time you reach 100 years old. So the radiation risk from x-rays is low, although not zero, of course. But medical societies recommend mammogram screening since they have shown to decrease risk of death from breast cancer when caught early. It’s all about weighing the risks and benefits. The risk of breast cancer development is higher than the potential harm that routine mammograms can present for most patients. 

Amount of Radiation per Diagnostic Test

Here are some common tests, and how many chest x-ray equivalents they may represent:


Diagnostic Test
Effective Dose of Radiation
(in Millisieverts)
Chest X-ray Equivalents
Chest X-ray
Low Back X-ray
Arm or Leg X-ray
Screening Mammogram
Head CT
Abdominal CT
Chest CT
1,000 – 2,000


See also: What Is Radiation?


Please note that all content here is strictly for informational purposes only. This content does not substitute any medical advice, and does not replace any medical judgment or reasoning by your own personal health provider. Please always seek a licensed physician in your area regarding all health related questions and issues.

About the Author

Sanaz Majd, MD

Dr. Sanaz Majd is a board-certified Family Medicine physician who graduated from Drexel University College of Medicine in Philadelphia. Her special interests are women's health and patient education.