Low bone density can develop without obvious symptoms, which is one reason bone health is often assessed before a fracture occurs. A DEXA scan, also written DXA, is a commonly used test for measuring bone mineral density at sites such as the hip and spine.

This article explains what a DEXA scan involves, who may be recommended to have one, how results are interpreted, and what can happen after testing. It is general health information only and is not a substitute for advice from your GP or another appropriately qualified health practitioner.

Why Bone Density Matters

Bone is living tissue that is continually remodelled. Bone mass generally reaches its peak in early adulthood, and bone loss becomes more common with ageing. In women, bone loss can accelerate around and after menopause.

When bone density becomes low enough, the bones can become more vulnerable to fractures. Osteoporosis is a condition in which bone strength is reduced and fracture risk is increased. Osteopenia describes bone density that is below the usual range but does not meet the densitometric definition of osteoporosis.

Bone health is influenced by many factors, including age, sex, family history, previous fractures, physical activity, nutrition, smoking, alcohol use, some medical conditions and some medicines.

Who May Be Recommended to Have a Bone Density Test?

In Australia, bone density testing is recommended for particular groups rather than automatically for everyone. Healthy Bones Australia recommends bone density testing for people aged 70 years and over, as well as for younger people in specified risk groups and for people who have experienced a minimal-trauma fracture.

Your GP may recommend a scan earlier if you have a condition, treatment or other risk factor that may affect bone strength. The appropriate timing depends on your individual risk profile, so a GP assessment can be more useful than relying on age alone.

Discuss your bone health with your GP if you have had a fracture after a relatively minor fall, have a family history of hip fracture, experienced early menopause, or have a medical condition or long-term medicine that can affect bone.

What Happens During a DEXA Scan?

You usually lie on your back on a padded table while a scanning arm moves over the body. For a standard bone-density assessment, measurements are commonly taken at the hip and lumbar spine. The radiographer positions you carefully because consistent positioning is important for accurate measurement and for comparison with future scans.

The scan is painless and does not normally require an injection. The appointment is usually relatively short, although the total time depends on the service and whether additional measurements are required.

DEXA uses a small amount of ionising radiation. The dose is low, but the test should still be performed when clinically appropriate. Tell the radiographer if you are or might be pregnant.

Vertebral Fracture Assessment

Some DEXA systems can produce a low-dose image of the spine called a vertebral fracture assessment. It may be considered in people at increased risk of vertebral fractures or where there is clinical suspicion of a previous compression fracture. Your clinician can explain whether this additional assessment is appropriate.

DEXA Is Not a Nuclear Medicine Bone Scan

A DEXA scan is different from a nuclear medicine bone scan. A nuclear medicine bone scan involves an injected tracer and is used for different clinical questions. DEXA measures bone mineral density and does not require an injected radioactive tracer.

What About Peripheral Bone Scanners?

Some devices estimate bone density or related measures at sites such as the heel, wrist or finger. These tests can have a role in particular settings, but their results should not be treated as interchangeable with a diagnostic DEXA assessment of the hip and spine.

How to Prepare

• You can generally eat and drink normally unless your imaging service gives you different instructions.
• Some services advise avoiding calcium supplements for the 24 hours before the scan. Follow the instructions provided by the imaging service.
• Tell the radiographer if you are or might be pregnant.
• Tell the radiographer about recent examinations involving contrast material, barium or nuclear medicine, because residual material can sometimes interfere with measurements and the appointment may need to be rescheduled.
• Mention metal implants or previous spinal surgery.
• Wear comfortable clothing and follow any instructions about metal items or clothing provided by the imaging service.

Understanding Your Results

For people for whom a T-score is appropriate, the result compares bone mineral density with that of a healthy young adult reference population. In postmenopausal women and men aged 50 years and over, the World Health Organization classification commonly used in clinical practice is:

• T-score above -1.0: within the normal range
• T-score between -1.0 and -2.5: low bone density (osteopenia)
• T-score of -2.5 or lower: osteoporosis by bone-density criteria.

For younger adults, Z-scores are generally more appropriate. A Z-score compares the result with people of a similar age and sex. A Z-score of -2.0 or lower is described as below the expected range for age and may prompt further assessment depending on the clinical context.

A bone-density number is not the same as an individual’s total fracture risk. Your doctor may also consider age, previous fractures, falls, family history, medical conditions, medicines and other risk factors before recommending management.

What Happens If Bone Density Is Low?

If your bone density is reduced, your clinician may review possible contributing factors and, where appropriate, arrange further assessment. This can include considering calcium and vitamin D intake, medical conditions, hormonal factors, medicines and previous fracture history.

Some people may be advised to make lifestyle changes, while others may be considered for medical treatment depending on their overall fracture risk. Any medicine recommended for bone health should be discussed in terms of its expected benefits, possible risks and monitoring requirements.

Calcium

Calcium is important for normal bone health. Australian guidance supports obtaining calcium from food where possible, with recommended intake varying according to age and circumstances. Useful dietary sources include dairy foods, calcium-fortified alternatives, calcium-set tofu and fish eaten with edible bones.

Vitamin D

Vitamin D supports calcium absorption and bone health. Sun exposure, diet and individual circumstances affect vitamin D status. Whether testing or supplementation is appropriate should be discussed with your clinician rather than assumed.

Exercise

Resistance training and appropriate weight-bearing or impact activity can help support bone and muscle health. People who already have osteoporosis, a previous fracture or significant pain may need an exercise plan adapted to their circumstances. A physiotherapist or accredited exercise physiologist can help with appropriate modifications.

Falls Prevention

Preventing falls is an important part of reducing fracture risk. Balance exercise, appropriate footwear, good vision and a safer home environment can all contribute.

Smoking and Alcohol

Smoking is associated with poorer bone health. Alcohol also contributes to health risks that increase with higher intake. The Australian guidelines recommend no more than 10 standard drinks a week and no more than 4 on any one day for healthy adults, with less alcohol reducing risk further.

How Often Should DEXA Be Repeated?

Bone density changes relatively slowly. A repeat scan is not automatically needed every year. The timing depends on your initial result, fracture risk and whether treatment or another clinical change needs to be monitored.

Repeating a scan too soon can make small differences difficult to interpret because measurement variability may be greater than the underlying biological change. Your clinician can advise on an appropriate interval.

Medicare and Referrals

Medicare rebates are available for certain bone densitometry services when the applicable eligibility criteria are met. These criteria depend on factors such as age, fracture history and relevant medical conditions, and referral requirements apply.

Because Medicare eligibility rules can change and depend on the specific MBS item, confirm current eligibility with your doctor or imaging provider before booking.

When to Speak With Your GP

Consider discussing bone health with your GP if you have experienced a fracture after a relatively minor fall, have significant risk factors for osteoporosis, or are concerned about your bone strength.

Seek medical assessment after a new injury, persistent back pain or a suspected fracture rather than relying on a DEXA result alone. A DEXA scan is one part of a broader clinical assessment.

Next Steps

If you are concerned about your bone health or believe you may meet criteria for testing, speak with your GP about whether DEXA testing is appropriate. Your doctor can consider your age, fracture history, medical conditions, medicines and other risk factors before recommending a scan.