DEXA stands for dual energy x-ray absorption. A DEXA scan is used to measure bone density by directing low-energy X-rays through the bone to measure its mineral density. Mineral density is an accurate predictor of bone strength. As compared with earlier methods, a DEXA scan offers a more precise, comfortable and safe examination. This painless exam precisely reports small changes in the body. It also is much more sensitive in measuring subtle changes in bones' response to drug therapy. Additionally, DEXA scans are less expensive and take less time to perform. A total body scan takes only four minutes to complete.