When it is used

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.

Identifying bone problems

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.

A DEXA scan also uses a low dose of radiation, which means the risks to health are much lower than with standard X-rays.

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:

• eating a healthy, balanced diet that's high in calcium
• spending more time in the sun to help increase your levels of vitamin D
• regularly doing weight-bearing exercise, such as walking or running

When a bone density scan is recommended

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:

• have had a broken bone after a minor fall or injury
• have a health condition, such as arthritis, that can lead to low bone density
• have been taking medicines called oral glucocorticoids for 3 months or more – glucocorticoids are used to treat inflammation, but can also cause weakened bones
• are a woman who has had an early menopause, or you had your ovaries removed at a young age (before 45) and have not had hormone replacement therapy (HRT)
• are a postmenopausal woman and you smoke or drink heavily, have a family history of hip fractures, or a body mass index (BMI) of less than 21
• are a woman and have large gaps between periods (more than a year)

Limitations

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).