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DEXA (dual energy X-ray absorptiometry) scan

Expert reviewer, Henry Maxwell, Consultant Orthopaedic Surgeon
Next review due August 2024

A DEXA (dual energy X-ray absorptiometry) scan measures the density of your bones to show how strong they are. It’s used to diagnose osteoporosis (fragile bones) or assess your risk of developing it. It gives your doctor information on how to reduce your risk of breaking a bone.

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What is a DEXA scan?

A DEXA scan, also known as a DXA or bone density scan, uses 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 fracture risk assessment, is used to predict how likely you are to have a fracture (broken bone) from osteoporosis.

A DEXA scan of your hip and spine is the ‘gold standard’ to diagnose osteoporosis and to predict your risk of breaking a bone. This is because your spine and hip are two of the most common places to break bones if you have osteoporosis.

Another type of DEXA scan is a peripheral DEXA scan. This uses a smaller, portable machine that can measure bone density in your wrist, heel or ankle. It can help to predict your risk of having another fracture but it’s not as good as a standard DEXA scan. But it may give your doctor an idea of whether or not you need to have a full DEXA scan or other tests.

You will normally have a DEXA scan at your local hospital. The scan is safe, quick and painless.

Assessing if you need a DEXA scan

Your GP or other health professional will need to refer you for a DEXA scan on the NHS. You may be able to get a DEXA scan at a private hospital or clinic without a referral from your GP. But, if this is the case, a qualified health professional will need to authorise it. Arrangements vary at different hospitals, so check what your hospital or clinic’s procedures are.

You’ll 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 can cause 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 is usually 65 and over for women and 75 and over for men
  • at an earlier age, if you have certain risk factors – for instance, if you have a low body mass index (BMI) or if you’re taking steroid tablets
  • because you’ve previously had a fragility fracture
  • if you’re a young woman who has had a number of stress fractures (a fracture caused by repeated stress on your bone)

Your doctor will use online tools to calculate your fracture risk. These take into account things that might increase your risk, including your medical history, age, sex, height, weight, and any medicines you take. The calculation also includes lifestyle factors such as whether or not you smoke, and how much alcohol you drink. This is because these factors also affect your bone density. The tools predict how likely it is that you’ll have a fracture due to osteoporosis in the next 10 years. If your risk is within a certain level, your doctor will advise you to have a DEXA scan.

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Preparing for a DEXA scan

You will usually have a DEXA scan at an outpatient clinic in your local hospital so you can have the scan and go home the same day. You don’t usually need to do anything before a DEXA scan.

Your hospital will tell you what to wear for a DEXA scan. 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. Your hospital team may ask you to change into a hospital gown. Follow any instructions that your hospital gives you.

Your 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 will run through some questions with you. For example, they may check:

  • the names of any medicines you take
  • if you’ve had any other scans recently that involved contrast or nuclear medicine (because these can affect the results of your DEXA scan)
  • if there’s any possibility you may be pregnant

They will also usually measure your height and weight.

Alternatives to a DEXA scan

There are other scans and tests that can help to find out how strong your bones are. But they’re not as good at measuring bone-mineral density as a DEXA scan. Other tests include:

  • a CT scan – this can accurately measure low bone mass, but involves a higher level of radiation than a DEXA scan
  • an ultrasound scan – this uses sound waves to look at your 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)

What happens during a DEXA scan

The scan itself will usually take between 10 and 20 minutes. But you’ll need to allow longer for your appointment because you may need other tests too.

Your health professional will ask you to lie on your back on a padded table during the scan. The table is open, so you won’t be enclosed in any way (in a tunnel, for example). The X-ray machine will be underneath you. It sends out invisible beams of radiation, which pass through your bones to a detector that’s positioned above your body. The detector has a long, thin ‘arm’, which will pass up and down the area being tested – usually your hips or spine.

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

It’s important to lie very still while you’re having the scan because if you move, the images will be blurred. You may need to change position, to make sure the machine can scan the right areas.

Sometimes, you may have another scan called a vertebral fracture assessment (VFA). This is done in the same way as a DEXA scan but can check for fractures in your spine. It will only take another few minutes to have this.

Getting your DEXA scan results

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

You will get two numbers from your DEXA scan: a T-score and a Z-score.

T-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.

Z-score

The Z-score compares your bone density with that of people your own age, size and sex.

If you have a low Z-score, particularly if you’re young, it 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 decide what to do next. They may ask you to have more tests to assess your bone health. These tests may include blood and urine tests and X-rays.

Osteoporosis treatment

If your results show that you have osteoporosis, your doctor will prescribe medicines to help slow down the rate at which you lose bone mass (density). We all lose bone mass as we get older but with osteoporosis, your body breaks down bone faster than it builds it up. Medicines can help to slow down bone loss.

Medicines include bisphosphonates. Your doctor will usually offer you a review after three to five years to see if these medicines are working. 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 to take any medicines if you’re diagnosed with osteopenia or told you’re at risk of developing osteoporosis. But your doctor will suggest some lifestyle changes you can make to help slow down the loss of bone mass and strengthen your bones.

These may include the following.

  • Eat a healthy, balanced diet, that includes plenty of calcium. Foods high in calcium include milk, cheese, yoghurt, sardines and calcium-fortified breads and cereals.
  • Get enough vitamin D because this helps your body to absorb calcium. Try to get out in the sun for a short time on a regular basis but take care not to burn your skin. You can also get vitamin D from the foods you eat. Vitamin D supplements are another option if you need them.
  • Keep active by doing some regular exercise – include 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.

Your hospital may ask you to come back for another scan within the next two years if your results showed you are 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, such as a chest X-ray. That said, 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’s a risk that the radiation could harm your baby.

Frequently asked questions

  • A DEXA scan measures the density of your bones to show how strong they are. It’s a test that doctors use to help diagnose osteoporosis. For more information, see our section: What is a DEXA scan? above.

  • There isn’t anything you need to do to prepare for a DEXA scan. You’ll have the scan and go home the same day. You may be able to stay fully dressed during the scan if you’re not wearing anything metal. But you may need to wear a hospital gown. For more information, see our section: Preparing for a DEXA scan above.

  • Your doctor will usually recommend you have a DEXA scan as part of an assessment for osteoporosis at age 65 and older (for women) and 75 and over (for men). They may advise you have it sooner if you’re at risk of osteoporosis or if you’ve previously had fragility or stress fractures. For more information, see our section: Assessing if you need a DEXA scan above.

  • The scan is safe, quick and painless and usually takes between 10 and 20 minutes. You’ll lie on your back on a padded table during the scan. An X-ray machine underneath you will send beams of radiation which pass through your bones to a detector that’s positioned above your body. For more information, see our section What happens during a DEXA scan above.

  • You may be able to keep your bra on but if it’s underwired you may need to take it off. Metal items can show up on the scan so you may need to remove them. Ask your hospital for advice. For more information, see our section: Preparing for a DEXA scan above.

  • There isn’t anything you should avoid before a DEXA scan. Your hospital will check if you’ve had any other scans recently that may affect the results of your DEXA scan. They’ll also check if you’re pregnant because there’s a risk the radiation could harm your baby. For more information, see our section: Preparing for a DEXA scan above.



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Related information


  • Discover other helpful health information websites.
    • Osteoporosis. BMJ Best Practice. bestpractice.bmj.com, last reviewed 3 July 2021
    • Osteoporosis – prevention of fragility fractures. NICE Clinical Knowledge Summaries. cks.nice.org.uk, last revised July 2021
    • Radiological guidance for the recognition and reporting of osteoporotic vertebral fragility fractures (VFFs). Royal College of Radiologists. www.rcr.ac.uk, published May 2021
    • Bone density scan. Royal Osteoporosis Society. theros.org.uk, accessed 3 August 2021
    • Bone densitometry (DEXA, DXA). Radiological Society of North America. www.radiologyinfo.org, reviewed 16 January 2020
    • Reporting dual energy X-ray absorptiometry scans in adult fracture risk assessment: Standards for quality. Royal Osteoporosis Society. theros.org.uk, published August 2019
    • Guidance to the ionising radiation (medical exposure) regulations 2017. Department of Health and Social Care. www.gov.uk, published June 2018
    • Long bone fracture. BMJ Best Practice. bestpractice.bmj.com, last reviewed 29 June 2021
    • SIGN 142 Management of osteoporosis and the prevention of fragility fractures. Scottish Intercollegiate Guidelines Network (SIGN). www.sign.ac.uk, revised January 2021
    • Personal communication, Henry Maxwell, Consultant Orthopaedic Surgeon, 17 August 2021
    • Stress fractures. Medscape. emedicine.medscape.com, updated 9 March 2020
    • Radiation dose in X-ray and CT exams. Radiological Society of North America. www.radiologyinfo.org, reviewed 20 March 2019
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    • Osteoporosis and diet: Food fact sheet. British Dietetic Association. www.bda.uk.com, published November 2019
    • UK Chief Medical Officers’ low risk drinking guidelines. Department of Health and Social Care. www.gov.uk, published August 2016
  • Reviewed by Rachael Mayfield-Blake, Freelance Health Editor, August 2021
    Expert reviewer, Henry Maxwell, Consultant Orthopaedic Surgeon
    Next review due August 2024

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