A Dual Energy X-ray Absorptiometry (DEXA) scan is a non-invasive procedure that uses very low levels of radiation to measure bone density. This test detects bone loss in its earliest stages and is the most effective way to diagnose osteoporosis. Dexa scans are accurate in assessing fracture risk or treatment needs. The exam takes only 15 to 20 minutes and is done on an outpatient basis.