A bone mineral density test uses X-rays to measure the amount of minerals in your bones, especially calcium. This is important for people at risk for osteoporosis, particularly women over 65 or those with a high risk of fractures. The test is also known as dual-energy X-ray absorptiometry (DXA). Osteoporosis causes your bone tissue to become thin and frail, leading to severe fractures. Your doctor may recommend a bone density test if they suspect your bones are becoming weaker, you have symptoms of osteoporosis, or you have reached the age for preventive screening. The test requires little preparation and involves lying on a table for the scan. The test results, known as a T-score, compare your bone density to that of a healthy 30-year-old.