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Harvard Medical School
There are a few small risks. The contrast dye that is sometimes used in the test can damage your kidneys, especially if they are already impaired by disease. If kidney damage does occur, this is usually temporary. If you are allergic to the dye used in the procedure, you may get a rash or your blood pressure may drop enough to make you feel faint until you get treatment. As with x-rays, there is a small exposure to radiation. The amount of radiation from a CT scan is greater than that from regular x-rays, but it's still too small to be likely to cause harm unless you're pregnant.