Bone density scan (DXA)

A bone density scan is used to measure how much bone tissue you have. This is known as your bone density. You may also hear this test called a DXA (or DEXA) scan.

You may be referred for a bone density scan if:

• you’ve broken a bone easily
• you have symptoms for spinal fractures
• you have risk factors for osteoporosis and broken bones
• your doctor needs to reassess your bone health and risk of breaking a bone, such as at a medication review.

The results from this scan are usually used alongside a fracture risk assessment to assess your risk of breaking a bone. By itself, a bone density scan can only tell your doctor how much bone tissue you have. It can't measure how strong your bone tissue is, or how likely you are to break a bone.

How does a DXA scan work?

In most cases, a bone density scan uses a type of X-ray called dual energy x-ray absorptiometry. This is shortened to DXA (or occasionally DEXA).

The scan uses a low radiation dose, so it's not harmful. It's similar to natural background radiation that you would expect on a transatlantic flight.

How long does a DXA scan take?

A DXA scan takes 10 to 20 minutes.

What to expect at your scan

A DXA scan is usually carried out by a radiographer, a DXA technician or a specially trained nurse.

You may have to change into a hospital gown before your scan.

Rest assured the procedure isn’t unpleasant. You don’t go into a tunnel, or need an injection.

In most cases, you're asked to lie on your back, on a firm couch. A scanning arm passes over your body and takes an image of your spine and hips - two of the most common places that bones break. You may be asked to move your legs so the machine can reach the right area.

Your results are usually available from your doctor, a few days later.

Vertebral fracture assessment (VFA)

This type of scan helps to identify broken bones in the spine without needing an additional x-ray.

It is sometimes carried out at the same time as your bone density scan, using the same machine. Although you may be referred for a VFA scan separately.

A VFA scan is similar to a bone density scan, although you may need to lie on your side for part of the procedure.

Understanding your DXA scan results

The results of your DXA scan tell your doctor how much bone tissue you have in the areas tested. This is also known as your bone density.

T-score

Results are given as a 'standard deviation', which is the number of units above or below the average bone density of a young and healthy person. This is known as your 'T-score'.

Whatever score you receive, your risk of breaking a bone increases as you grow older. By the age of 75, 50% of the population has a bone density in the osteoporosis range.

What your T-score means

• +1 to -1 - Your bone density is in the normal range for a young and healthy person.
• -1 to -2.5 - Your bone density is slightly below the normal range for a young and healthy person, also known as osteopenia.
• -2.5 and below - Your bone density is in the osteoporosis range.

If your T-score is in the osteoporosis range, it doesn't always need to be a cause for concern. It doesn't necessarily mean you will break a bone, or need a treatment. Having low bone density is one risk factor for osteoporosis and broken bones.

Your results from this test are usually used alongside a fracture risk assessment, which takes these other risk factors into account.

Z-score

You may be given your results as a Z-score, alongside your T-score.

A Z-score compares your bone density to people of the same age as you.

Having a low Z score may indicate that another condition or medicine is affecting your bone density levels. In this situation your doctor suggests further tests.

After your scan

If your T-score is in the osteoporosis range, or you have other risk factors for osteoporosis, such as:

• you’ve broken a bone easily
• you're taking a medication or have a medical condition that is known to affect bone strength
• you have a combination of a number of other risk factors for osteoporosis

- it's likely you also need a fracture risk assessment. This test takes into account all your osteoporosis risk factors, including your bone density, to calculate your risk of breaking a bone.

The results of your fracture risk assessment tell your doctor whether you need an osteoporosis medication. If your risk of breaking a bone is high, they can consider a treatment to help strengthen your bones.

If your T-score is in the normal or osteopenia range, and you don't have any other risk factors for osteoporosis, you don't need further tests, or a treatment.

Your doctor may suggest another scan in the future, to monitor your bone health. They can also offer lifestyle advice, to help you protect your bones.

Watch our discussion: 

Consultant Radiographer, Jill Griffin, explains what a bone density scan (DXA) is and what the results mean for you. This film is part of our #BoneMatters series of events

Watch our discussion on DXA and other osteoporosis scans: 

If you would like to find out more about the different types of scans for osteoporosis, you may be interested in watching a conversation with consultant radiographer, Jill Griffin. This film is part of our #BoneMatters series of events