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Harvard Medical School
Risks from this test are minimal. A few people have an allergic reaction to the dye used in the test. Some people have a headache or back soreness for a short time.
As with x-rays, there is a small exposure to radiation. In large amounts, exposure to radiation can cause cancers or (in pregnant women) birth defects. The amount of radiation from a CT scan is larger than from regular x-rays, but still very small—too small to be likely to cause any harm.