The short answer
Some imaging tests, like CT scans and x-rays, use ionizing radiation, which carries a small cancer risk. For most people the benefit of a needed scan far outweighs the risk. MRI and ultrasound use no ionizing radiation.
Medical imaging radiation is classified as a known human carcinogen (IARC Group 1).
People are mainly exposed by undergoing x-ray and CT imaging tests.
It is most strongly linked to a small added risk of leukemia and solid cancers.
A carcinogen classification describes hazard — whether something can cause cancer — not your personal risk at a given exposure.
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The full explanation.
The simple version
Medical imaging such as x-rays and CT scans uses small amounts of ionizing radiation to see inside the body. That radiation carries a very small added cancer risk. Still, a scan your doctor recommends usually brings benefits that far outweigh the risk. Some tests use no ionizing radiation at all, including MRI and ultrasound.
What medical imaging radiation is
X-rays and CT scans pass ionizing radiation through the body to make images. Doses are generally low, though CT delivers more than a plain x-ray. MRI and ultrasound do not use ionizing radiation. Doctors follow the principle of using the lowest reasonable dose.
How people are exposed
Common ways people come into contact with it:
- CT scans, x-rays, and some nuclear-medicine tests.
- Cumulative exposure builds up with many repeated scans.
- Children are more sensitive to radiation than adults.
The cancer connection
Ionizing radiation from imaging carries a small added lifetime risk of cancer. Leukemia and solid tumors are the main examples. The risk rises with dose and with the number of scans.
IARC places medical imaging radiation in Group 1, carcinogenic to humans. That is its strongest evidence category. It means there is enough evidence that this radiation can cause cancer in people. IARC is the cancer research agency of the World Health Organization. In the United States, the National Toxicology Program lists X-radiation and gamma radiation, the kinds used in medical imaging, in its Report on Carcinogens as known to be human carcinogens.
Hazard is not the same as risk
Two ideas are easy to mix up: hazard and risk. Calling imaging radiation a carcinogen speaks to hazard. Hazard is whether something can cause cancer under some conditions. That is not the same as your personal risk. Your risk depends on how much you are exposed to, for how long, and other factors. Group 1 covers agents whose everyday risks are nothing alike. The label says a thing can cause cancer. It does not say how likely that is for you.
How to lower your exposure
- Ask if a scan is needed, and whether MRI or ultrasound could work instead.
- Use facilities that follow child-appropriate, low-dose protocols.
- Keep a record of past imaging so tests are not repeated for no reason.
- Do not skip scans your doctor considers important out of fear.
Thinking about your overall cancer risk? Small, steady steps add up. To see where medical imaging radiation sits among all the things that affect cancer risk, read our overview of cancer prevention and what raises cancer risk.
The bottom line
Medical imaging radiation is a known human carcinogen (IARC Group 1). What helps most is knowing where exposure comes from. Take reasonable steps to limit it, and do not lose sleep over a single label. Put your energy into the biggest risks you can control.
Words to know
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Common questions
Does medical imaging radiation cause cancer?
Yes. Medical imaging radiation is classified as a known human carcinogen, which means there is strong evidence it can cause cancer in people. How much any one person's risk rises depends on how much they are exposed to and for how long.
How are people exposed to medical imaging radiation?
Most exposure happens by undergoing x-ray and CT imaging tests.
Which cancers are linked to medical imaging radiation?
It is most strongly linked to a small added risk of leukemia and solid cancers. For any single, medically needed scan, the risk is very small and usually outweighed by the benefit of a correct diagnosis.
How can I reduce my exposure to medical imaging radiation?
The main steps are using imaging only when needed and choosing lower-dose options.
Does a carcinogen label mean I will get cancer?
No. A classification is about hazard — whether medical imaging radiation can cause cancer under some conditions — not a prediction that any one exposed person will develop cancer. Your actual risk depends on the amount and length of exposure and other factors.
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Last updated: 2026-08-10Next planned review: 2028-07-05
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How this page was created
Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes. We do not employ clinicians and do not intend to — our work is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and checked line by line against the sources listed on it. That confirms the sources support what the page says. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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