Bone density scans, also known as DEXA scans, help to work out your risk of breaking a bone.
They're often used to help diagnose bone-related health problems, such as osteoporosis, or to assess the risk of getting them.
Total body bone density scans can also be used to measure the amount of bone, fat and muscle in the body.
This type of scan is routinely used in children, but is only used as part of a research study in adults.
Unlike ordinary X-rays, DEXA scans can measure tiny reductions in bone density.
This makes it possible to diagnose osteoporosis in its early stages, before you break a bone.
Doctors use the results of bone density scans to help them decide whether treatment for low bone density is needed.
This may include making lifestyle changes to help improve your bone health, such as:
A DEXA scan may be recommended if you have an increased risk of developing a bone problem like osteoporosis.
Your risk is increased if you:
A DEXA scan is not the only way of measuring bone strength. Other risk factors, such as family history and certain medicines, help to work out if you're at risk of breaking a bone.
All of the risk factors need to be considered before you have a bone density scan or start treatment.
Some people need a bone density scan to confirm that their risk of breaking a bone is high enough to need treatment.
For others, particularly older people over the age of 75, the risk of breaking a bone may be so high that there's no need for them to have a bone density scan before treatment is prescribed.
Interpreting the results of a bone density scan can sometimes be difficult.
For example, it may not be easy to interpret the results of a scan of the spine when someone has a degenerative condition, such as osteoarthritis of the spine (spondylosis).
Sometimes spinal abnormalities or a previous spinal fracture can give a false result.
A bone density scan will not show whether low bone mineral density is caused by too little bone (osteoporosis) or too little calcium in the bone, usually because of a lack of vitamin D (osteomalacia).