Bone density scanning

A bone density scan measures quantity of bone tissue, usually in one hip and the lower part of the spine, using a densitometry x-ray (DEXA).

Bone density can also be measured through a computerised tomography (CT) scan, although this is less common.

You can find information about what to expect from a DEXA scan, what the results mean, and what might happen after a DEXA scan below. Further information can be found on the bone density scanning factsheet.

 Download the bone density scanning and osteoporosis factsheet

What to expect from a DEXA scan

A DEXA scan takes about 10 to 20 minutes and isn’t unpleasant – it doesn’t involve going into a ‘tunnel’ or having an injection.

An individual is scanned lying on their back, on a firm couch, while a scanning arm passes over the body, taking an image of the spine and hips. The legs will be supported in a certain way, such as on a large cushion or supporting arm, to make sure they are in the correct position for the part of our body being scanned.

Each hospital will have its own procedure – some may ask for a hospital gown to be work, although clothing without metal zips and fasteners may avoid the need for this.

Understanding DEXA scan results

Bone density scan results are usually given as a ‘standard deviation’ (SD) – the number of units above or below average.

A bone density of 2.5 SD below average, or less, is described as ‘osteoporosis’, whilst a bone density of between the lower end of the normal range and -2.5 SD is described as ‘osteopenia’.

A bone density scan result isn’t a measure of our overall bone strength, but our bone density – the ‘quantity’ of bone tissue we have. Bone density is just one risk factor taken into consideration when calculating our risk of breaking a bone.

Research has now proved that overall bone strength can be assessed more accurately by a fracture risk assessment (FRAX), which combines the results of our bone density scan with other proven risk factors for fracture.

 More about fracture risk assessments