Bone Density Scan (DEXA): What to Expect and How to Prepare

The full name is dual-energy X-ray absorptiometry, usually shortened to DEXA or DXA. The machine passes two low-energy X-ray beams through the bone and measures how much of each is absorbed. The difference between them is what separates bone from the soft tissue around it, and produces a number.

You lie on a padded, open table while an arm passes above you. There is no tunnel, no injection and nothing to swallow, and the table is open on all sides.

Doctors commonly request one to look into bone strength after a fracture from a minor injury, where there is a family history, where a medical condition or a long-term medicine is known to affect bone, or as part of assessing bone health with age.

The spine and one or both hips are the sites usually measured, because those measurements have been shown to be the most useful for estimating fracture risk. A forearm may be measured instead if the hip or spine cannot be used — after a joint replacement, for example.

Whether you need this scan, and how often, is a decision for the doctor who referred you. This page does not answer that question.

• No fasting is needed, and there is no reason to change any medicine for this scan.
• Wear something loose with no zips, studs, buckles or metal fastenings around the waist and hips — metal sits in the measured area and interferes with the result.
• Empty your pockets of keys, coins and your phone, and leave off metal jewellery around the waist.
• You will usually stay in your own clothes. A gown is provided if what you are wearing would affect the measurement.

Metalwork does not usually stop the scan — it means the radiographer measures a different site, and knowing in advance saves repeating the appointment.

• your referral, if it has not already been sent to the clinic
• your Medicare card, and any concession or DVA card
• the report or images from any earlier bone density scan, especially if it was at a different practice
• a list of your current medicines, including any you take for bone health
• the name of the doctor who should receive the report

The radiographer positions you carefully, and this is the part that takes the time. For the spine, a padded box is usually placed under your knees so your lower back lies flat against the table. For the hip, your foot is held in a brace that rotates the leg into a set position.

That precision is the point. A bone density result is most useful compared with your own earlier result, and that comparison only holds if you were positioned the same way each time. It is also why going back to the same practice, on the same machine, is worth doing where you can.

You need to stay still and breathe normally while the arm passes over each area, which takes a minute or two per site. The dose is low enough that the radiographer usually stays in the room with you.

Allow a little longer for check-in and for any paperwork about your bone health history, which the practice may ask you to complete. If a third site such as the forearm is needed, add a few minutes.

The only discomfort people report is from lying flat, or from having a leg held in the positioning brace if a hip or back is already sore. Tell the radiographer — the position can usually be adjusted or padded.

The dose used is small against the ionising radiation everyone receives continuously from natural sources such as the ground, building materials, food and cosmic rays.

As with any test that uses X-rays, tell the clinic if you are or might be pregnant, and the decision about whether to proceed or wait is made by your doctor and the practice.

There is nothing left in your body afterwards, and the scan does not make you radioactive.

You will receive numbers rather than pictures: a bone mineral density for each site measured, and scores comparing you with a reference population. Where you have been scanned before, the report also shows the change since then.

A score is only one input. Your doctor weighs it with your age, your history of fractures, family history, other conditions, and the medicines you take, to form a view of your overall fracture risk. That is why this page does not tell you what any particular number means — the same score can lead to different conversations for different people.

Book a follow-up with your referring doctor to go through the report rather than waiting to be contacted, and ask at that appointment whether and when the scan should be repeated.

You can drive, eat and return to work straight away. Nothing was injected and nothing remains in your body.

Any changes to exercise, diet, supplements or medicines are conversations to have with your doctor once they have the report — not steps to take on the strength of a scan result. If you become unwell, contact your doctor. In an emergency, call 000.

In Australia, medical imaging is arranged through a referral (also called a request) from a doctor. You take that referral to an imaging provider, and for most types of imaging you may choose which provider you go to, unless your referral names one.

Bone density scanning is one of the areas where Medicare eligibility depends on specific circumstances — age, certain medical conditions, and certain treatments — and on how recently you were last scanned. Because those rules are set out in the Medicare Benefits Schedule and change from time to time, this page does not restate them.

• Ask your referring doctor whether your scan meets the Medicare requirements — they are the person who can check.
• Ask the imaging provider what the scan will cost you before you book, and whether they bulk bill it.
• Services Australia publishes current information on Medicare and bulk billing, and MBS Online publishes the Medicare Benefits Schedule itself. Both are linked in the sources below.