DEXA (dual energy X-ray absorptiometry) scan

Expert reviewer, Henry Maxwell, Consultant Orthopaedic Surgeon
Next review due May 2022

A DEXA (dual energy X-ray absorptiometry) scan measures the density of your bones to show how strong they are. It can be used to diagnose osteoporosis (fragile bones) or to assess your risk of developing this condition. Then, if necessary, your doctor can suggest measures to reduce your risk of breaking a bone.

A DEXA scan is sometimes referred to as a DXA or a bone density scan.

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What is a DEXA scan?

DEXA scans use very low levels of X-ray radiation to produce images of your bones. It detects how much radiation is absorbed by your bones, which shows how dense they are. This, plus a risk assessment carried out by your doctor, is used to predict how likely you are to have a fracture due to osteoporosis.

A DEXA scan of your hip and spine is considered to be the ‘gold standard’ for diagnosing osteoporosis and predicting future fracture risk. Your spine and hip are two of the most common places to break bones if you have osteoporosis.

A DEXA scan will normally be carried out at hospital. These scans are safe, quick and painless.

Assessing whether you need a DEXA scan

You will usually only be invited to have a DEXA scan if your doctor has assessed you as being at risk of fragility fractures. A fragility fracture is when your bones become weakened due to osteoporosis, so that even a minor bump or fall causes them to break.

Your doctor may ask you to have a fracture risk assessment:

  • when you reach a certain age (this can vary between areas and practices, but may be over 65 for women and over 70 for men)
  • at an earlier age, if you’re known to have certain risk factors – for instance, if you have a low Body Mass Index (BMI) or if you’re taking glucocorticoids – a type of steroid medicine.
  • because you’ve previously had a fragility fracture

Doctors use special online tools to calculate your fracture risk. These take into account factors that might increase your risk, including your medical history, age, sex, height, weight, and any medication you’re on. The calculation also includes lifestyle factors such as if you smoke and how much alcohol you drink because these also affect your bone density.

The tools predict how likely it is you’ll have a fracture due to osteoporosis in the next 10 years. If it looks like your risk may be within a certain level, your doctor will advise you to have a DEXA scan.

Preparing for a DEXA scan

It may take a few weeks to get an appointment for a DEXA scan, depending on your local hospital. They are usually done at an outpatient clinic, which means you won’t need to be admitted to hospital. Arrangements for scans and how they’re carried out may vary between hospitals, so you should follow any instructions you’re given. You don’t usually need to make special preparations for a DEXA scan.

The scan may be done by a radiographer (a health professional trained to perform imaging procedures), a DEXA technician or a specially trained nurse. When you arrive at the hospital, they are likely to run through some questions with you. These may include:

  • checking the names of any medicines you’re taking
  • checking whether you’ve had any other scans recently involving contrast or nuclear medicine (because these can affect the results of your DEXA scan)
  • if you’re a woman of child-bearing age, checking whether there’s any possibility you may be pregnant

They will also usually measure your height and weight. You may be able to stay fully dressed during the scan if you’re not wearing anything metal. Metal buttons, zips or jewellery could show up on the scan. You’ll need to take any keys and wallets out of your pockets and remove any other metal objects such as glasses, piercings or dental appliances. If necessary, you’ll be asked to change into a hospital gown.

Alternatives to a DEXA scan

There are a number of other scans and tests that can help to find out how strong your bones are. These include:

  • a CT scan – this can accurately measure low bone mass, but has a higher level of radiation than a DEXA scan
  • an ultrasound scan– this uses sound waves to look at bone structure and strength
  • a standard X-ray – this can show if you have any fractures and may reveal if you have weak bones (osteopenia)

These alternative tests aren’t as good at measuring bone-mineral density as a DEXA scan.

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What happens during a DEXA scan

The scan itself will usually take between 10 and 30 minutes. But you’ll need to allow around two hours for your appointment because you may need other tests too.

You’ll be asked to lie on your back on a padded table during the scan. Unlike some other types of scan, you won’t be enclosed in any way (in a tunnel, for example).

The X-ray machine is located underneath you. It sends out invisible beams of radiation, which pass through the bones being examined, to a detector positioned above your body. The detector has a long, thin ‘arm’, which is passed up and down the area being tested – usually your hips or spine.

The detector measures the amount of radiation it receives that has passed through your bones. This information is then used to generate images on a computer monitor. This shows how dense your bone is.

It’s important to lie very still while the scan is being done to stop the images from being blurred. You may be asked to change position, to make sure the right areas can be scanned.

Sometimes, you may have an additional scan, called a Vertebral Fracture Assessment (VFA). This is carried out in the same way as a DEXA scan but is used to check for fractures in your spine. It only adds a few extra minutes to a normal DEXA procedure.

Getting your DEXA scan results

A radiologist – a doctor specially trained to interpret X-ray images – will analyse your results. They’ll send their findings in a report to your GP or the doctor who referred you for the scan. You should be told when to expect your results and how to get them before you leave your appointment. It will generally take a few days.

You will get two numbers from your DEXA scan: a T-score and a Z-score. The T-score compares your bone density to the average for a young, healthy person.

  • A T-score of between 0 and –1 means your bone density is in the normal range for a young, healthy person.
  • If your T-score is between –1 and –2.5, your bone density is slightly lower than normal for a young, healthy person. This is known as osteopenia.
  • A T-score below –2.5 is classed as osteoporosis.

The Z-score compares your bone density with that of people your own age, size and sex. A low Z-score, particularly if you’re young, can indicate that there might be something that’s affecting your bone density levels. This might be another condition or medicine you’re taking.

What happens next?

Your doctor will look at your DEXA scan results together with your fracture risk assessment to recommend any further actions. They may ask you to have further tests to assess your bone health, including blood and urine tests, and X-rays.

Osteoporosis treatment

If the results of your tests show that you have osteoporosis, you’ll be offered medication to help strengthen your bones. This might include bisphosphonates as well as calcium and vitamin D supplements. Treatment with bisphosphonates may be reviewed after three to five years. You may be asked to have another DEXA scan after this time, to see if your bone health has improved.

Lifestyle advice

You won’t need treatment if you’re diagnosed with osteopenia or told you’re at risk of developing osteoporosis. Your doctor will suggest some lifestyle changes to help strengthen your bones.

These may include the following.

  • Make sure you’re eating a healthy, balanced diet, including plenty of calcium. Foods high in calcium include milk, cheese, yoghurt, sardines and calcium-fortified breads and cereals.
  • Make sure you’re getting enough vitamin D, as this helps your body absorb calcium. Try to get regular, brief exposure to the sun, without letting your skin burn. You may want to consider taking a vitamin D supplement too because it’s hard to get enough from your diet.
  • Keep active by taking regular exercise – including weight-bearing exercise, such as walking – every day.
  • If you smoke, try to stop because smoking increases the risk of fragility fractures.
  • If you drink alcohol, stick to the recommended limit of no more than 14 units a week.

You may be asked to come back for another scan within the next two years if you were found to be at risk of developing osteoporosis.

Risks of a DEXA scan

Although any procedure carries a certain amount of risk, DEXA is a very safe procedure, with no real risk of complications.

The scan will expose you to some X-ray radiation. Radiation can be harmful to your body if you have a high dose. But the amount you’re exposed to in a DEXA scan is very low – much less than you’d get in other tests (for example, in a chest X-ray). It is comparable to a few hours of natural background radiation. This won’t be harmful.

If you’re pregnant or think you might be, it's important to let your doctor or radiographer know. You might not be able to have a DEXA scan because there is a risk that the radiation could harm your unborn baby.

Frequently asked questions

  • A peripheral DEXA scan uses a smaller, portable machine that can measure bone density in your wrist, heel or ankle. Your doctor may suggest it if you’ve broken a bone in one of these areas – for instance, your wrist. It can help to predict your risk of having another fracture but it’s not as good as a standard DEXA scan for this. It may help your doctor decide about starting treatment and give an idea of whether or not a full DEXA scan or other tests are necessary

  • You will need a referral from a GP or other health professional for a DEXA scan on the NHS. Your GP will refer you for one if they’ve assessed you as being at risk of fragility fractures. Sometimes, you may already be seeing a hospital consultant if you’ve had a broken bone or are attending a fracture clinic. They may suggest a DEXA scan to check how fragile your bones are.

    You may be able to get a DEXA scan at a private hospital or clinic without a referral from your GP. However, it will need to be authorised by a qualified health professional. Arrangements will vary at different hospitals and in different areas. You’ll need to check with the hospital or clinic what their procedures are.

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Related information

    • Musculoskeletal problems. Oxford handbook of general practice. Oxford Medicine Online., published online April 2014
    • Osteoporosis. BMJ Best Practice., last reviewed February 2019
    • Osteoporosis: assessing the risk of fragility fracture. National Institute for Health and Care Excellence (NICE), August 2012.
    • Bone mineral density. Encyclopaedia Britannica., accessed 26 March 2019
    • Bone density scan. Royal Osteoporosis Society., accessed 26 March 2019
    • Bone densitometry (DEXA, DXA). Radiological Society of North America., reviewed 10 August 2018
    • Guidelines for the provision of a clinical bone densitometry service. National Osteoporosis Society, August 2014.
    • Osteoporosis. Oxford handbook of geriatric medicine. Oxford Medicine Online., published online February 2018
    • Osteoporosis risk assessment and primary prevention. PatientPlus., last reviewed 12 October 2015
    • FRAX® Fracture Risk Assessment Tool. Centre for Metabolic Bone Diseases, University of Sheffield, UK., accessed 26 March 2019
    • QFracture® 2016 risk calculator. ClinRisk., accessed 26 March 2019
    • Monthly diagnostics commissioner. January 2019. NHS England National Statistics, published 14 March 2019.
    • Scans, tests and results. Royal Osteoporosis Society., accessed 5 April 2019
    • Radiation dose in X-Ray and CT exams. Radiological Society of North America., reviewed 20 April 2018
    • Osteoporosis – prevention of fragility fractures. NICE Clinical Knowledge Summaries., last revised December 2016
    • Osteoporosis. Quality standard. National Institute for Health and Care Excellence (NICE), April 2017.
    • Calcium. British Dietetic Association, July 2017.
    • Vitamin D deficiency in adults – treatment and prevention. NICE Clinical Knowledge Summaries., last revised September 2018
    • Management of osteoporosis and the prevention of fragility fractures. Scottish Intercollegiate Guidelines Network (SIGN), March 2015.
    • A guide to understanding the implications of the Ionising Radiation (Medical Exposure) Regulations in diagnostic and interventional radiology. The Royal College of Radiologists, 2015.

  • Reviewed by Pippa Coulter, Freelance Health Editor, May 2019
    Expert reviewer, Henry Maxwell, Consultant Orthopaedic Surgeon
    Next review due May 2022