A bone density scan, also known as a bone mineral density (BMD) test, is a type of medical imaging exam that measures the density of bones in your body. The exam is used to assess the strength of your bones and to detect osteoporosis, a condition that weakens bones and makes them more prone to fractures.

A bone density scan is typically performed using a special machine called a dual-energy x-ray absorptiometry (DXA) scanner. During the exam, you lie on a table while the DXA scanner moves over the area being examined, such as the hip or spine. The scanner emits low-dose x-rays that pass through your bones and are absorbed differently by bones of different densities.

Bone density scans are safe, noninvasive, and painless. They are typically recommended for people over the age of 65, postmenopausal women, and people with certain medical conditions that increase their risk of osteoporosis. The exam can be repeated periodically to monitor the progression of osteoporosis and the effectiveness of treatment.