In search of a diagnosis for my persistent low-back pain, my doctor recently ordered several X-rays of my spine. Do multiple X-rays increase my risk of developing cancer? —P.B., Clemson, S.C.

Yes. While nearly all X-rays expose you to radiation that increases your cancer risk, a low-back X-ray can expose you to relatively high doses. Moreover, those tests are often unnecessary, since nearly all low-back pain stems from muscles, ligaments, and nerves, which don't appear on X-rays. And most low-back pain eventually resolves on its own with simple self-help measures, including mild painkillers and cold packs.

In general, agree to imaging tests only if the pain doesn't respond to self-help methods or physical therapy and lasts for more than a month, or if you also have any of the following: leg weakness; pain radiating from the buttock to the thigh, knee, or lower leg; a history of osteoporosis, or a recent fall or accident; fever, night sweats, or unexplained weight loss; or a history of cancer or incontinence.

This article first appeared in the August 2008 issue of Consumer Reports on Health.

Find out when you should consider an X-ray for pain (free), see our whole-body guide on imaging tests (free), and take a look at our Treatment Ratings for back pain (subscribers only).