Bone health can change without obvious symptoms, which is one reason it may not receive much attention until a fracture or another concern occurs. A DEXA scan, also known as a DXA scan, is a commonly used test for measuring bone mineral density (BMD).

A DEXA scan can provide useful information about bone density and can contribute to an assessment of fracture risk. However, it does not provide a complete picture of bone health on its own. Age, previous fractures, falls, medications, medical conditions and other risk factors can also influence fracture risk and how a result is interpreted.

What Is A DEXA Scan?

DEXA stands for dual-energy X-ray absorptiometry. The test uses low-dose X-rays to measure bone mineral density, usually at areas such as the hip and lumbar spine.

The scan is non-invasive and generally painless. You typically lie still while the equipment collects measurements from the areas being assessed.

The results are usually reported using scores that help compare a person’s bone density with reference populations. The two scores most commonly discussed are the T-score and Z-score.

What Is A T-score?

A T-score compares bone mineral density with that of a healthy young adult reference population.

In general, a T-score of -1 or above is considered within the normal range. A score between -1 and -2.5 is classified as low bone density, commonly referred to as osteopenia, while a T-score of -2.5 or below meets the bone-density criterion used to classify osteoporosis in the populations for which T-score classification applies.

What Is A Z-score?

A Z-score compares bone density with an age-matched reference population.

It can provide additional context, particularly when a clinician is considering whether factors other than normal ageing may be contributing to lower bone density.

Neither score should be interpreted completely on its own. A clinician may consider the DEXA result alongside fracture history, age, falls, medications, medical conditions and other relevant risk factors.

Osteopenia And Osteoporosis

Osteopenia describes bone mineral density that is lower than the young-adult reference range but does not meet the T-score threshold used to classify osteoporosis.

Osteopenia is a description of bone density rather than a guarantee that osteoporosis will develop. Some people with low bone density may have other risk factors that influence their overall fracture risk, while others may have relatively few additional risks.

Osteoporosis is characterised by reduced bone strength and an increased risk of fragility fractures. DEXA measurements can contribute to the assessment of osteoporosis, but fracture risk is influenced by more than bone mineral density alone.

What Can A DEXA Scan Tell You?

A DEXA scan can provide an objective measurement of bone mineral density at the sites examined.

It can help identify whether bone density is within the expected range, lower than expected, or within the range used to classify osteoporosis.

A DEXA result can also provide a baseline for future comparison when repeat testing is clinically appropriate. Comparing measurements over time may help a clinician assess changes in bone mineral density.

However, a DEXA scan does not measure every aspect of bone strength. Factors such as bone quality, previous fractures, falls and other health conditions can also contribute to fracture risk.

What A DEXA Scan Cannot Tell You On Its Own

Although DEXA is a useful assessment tool, it is not a complete measure of overall bone health.

A result cannot independently determine whether someone will or will not experience a fracture. It also cannot identify every possible reason for low bone density.

Depending on the individual, further assessment may consider medical history, medications, nutritional factors, hormonal factors and medical conditions that can affect bone health.

Similarly, a single DEXA result cannot automatically determine whether a treatment has succeeded or failed. Changes in bone mineral density need to be interpreted in relation to the expected measurement variability, the time between scans and the person’s broader clinical circumstances.

Why Fracture Risk Matters

The practical importance of bone density relates partly to its association with fracture risk. Fragility fractures can affect mobility, independence and quality of life, particularly in older adults.

Low bone mineral density is an important risk factor, but it is not the only one. Age, previous fractures, falls, medications and other health factors may all contribute to an individual’s overall risk.

This is why clinicians may consider DEXA results together with other clinical information when deciding whether further assessment or treatment should be considered.

Who May Need A DEXA Scan?

DEXA testing is not necessarily appropriate for everyone as a routine screening test. Whether it is useful depends on factors such as age, fracture risk, medical history and whether the result is likely to influence management.

Factors that may lead a clinician to consider bone-density testing include a previous fragility fracture, older age, low body weight, certain medical conditions, reduced sex hormone levels and medicines that can affect bone health, including prolonged corticosteroid exposure.

Menopause is also relevant to bone health because bone loss can accelerate around the menopausal transition. However, the decision to perform a DEXA scan should be individualised rather than based on menopause alone.

If you are unsure whether a DEXA scan is appropriate, discuss your individual risk factors with your doctor or another suitably qualified health professional.

Keeping Track Of Bone Density Over Time

Repeat DEXA testing can sometimes be useful, particularly when there is a clinical reason to monitor changes in bone mineral density.

The appropriate interval is not the same for everyone. Repeat testing should take into account fracture risk, the reason for monitoring and whether a meaningful change is likely to influence management.

In many circumstances, testing at intervals shorter than approximately two years may provide limited additional information because changes in bone mineral density can be smaller than the expected measurement variability. Some higher-risk situations may require a different approach.

Where possible, follow-up measurements are generally easier to compare when performed using the same machine or a comparable system with appropriate quality control.

Ways To Support Bone Health

Bone health is influenced by a combination of nutrition, physical activity, medical conditions, medications and lifestyle factors. There is no single approach that is appropriate for everyone.

Nutrition

Adequate calcium and vitamin D are important for maintaining normal bone health.

Calcium can be obtained from foods such as dairy products, fortified alternatives and some leafy green vegetables. Vitamin D status is influenced by several factors, including sunlight exposure, diet and individual health circumstances.

Supplements may be appropriate for some people when dietary intake is inadequate or when a healthcare professional identifies a specific need. Supplementation should not be treated as a universal substitute for an overall assessment of diet and health.

Weight-Bearing And Resistance Exercise

Weight-bearing and resistance exercise can form part of a broader approach to maintaining bone and muscle health.

Activities may include walking, stair climbing, resistance training and other suitable forms of exercise, depending on a person’s age, fitness, health status and physical ability.

Strength and balance exercises can also contribute to falls-prevention strategies. People with osteoporosis, previous fractures or other relevant health concerns may benefit from individual exercise advice before increasing exercise intensity.

Smoking And Alcohol

Smoking and higher levels of alcohol consumption are recognised risk factors associated with poorer bone health.

Reducing these modifiable risk factors can form part of a broader strategy for maintaining bone health.

Medical Review

Some medical conditions and medicines can affect bone density or fracture risk.

If a DEXA result is lower than expected, a clinician may consider whether further assessment is appropriate to identify potentially relevant medical, nutritional or medication-related factors.

DEXA And Healthy Ageing

Bone health is relevant to healthy ageing because fractures can affect mobility and independence.

Maintaining physical function involves more than bone mineral density alone. Strength, balance, physical activity, nutrition, medical conditions and falls risk can all influence how a person functions as they age.

A DEXA scan can therefore provide one useful piece of information within a broader assessment rather than acting as a test that predicts lifespan or guarantees future independence.

Common Myths About Bone Density

“I Feel Fine, So My Bones Must Be Fine.”

Low bone density often does not cause noticeable symptoms. This is one reason risk assessment and clinically appropriate testing may be useful for people who have relevant risk factors.

“Men Do Not Get Osteoporosis.”

Men can develop osteoporosis and experience fragility fractures. Although osteoporosis is more common in women, bone health can also be relevant for men when appropriate risk factors are present.

“A DEXA Scan Gives You The Whole Answer.”

A DEXA scan measures bone mineral density at selected sites. Fracture risk is multifactorial, so the result needs to be interpreted alongside other relevant clinical information.

“Calcium Supplements Are All I Need.”

Calcium is important for bone health, but other factors also matter, including vitamin D, physical activity, body weight, medical conditions, medications and falls risk.

Whether supplementation is appropriate depends on the individual’s circumstances rather than a one-size-fits-all approach.

The Role Of Assessment And Clinical Context

A DEXA result is most useful when interpreted in the context of the person being assessed.

A suitably qualified health professional can consider the scan alongside relevant medical history, fracture history, medications, lifestyle factors and other measures of fracture risk.

For health services that provide DEXA or broader health assessments, information should clearly explain what the test can and cannot establish. A scan should not be presented as necessary for everyone or as a guarantee that future bone problems will be prevented.

Pulling It Together

DEXA is an established method for measuring bone mineral density and can provide useful information when assessing osteoporosis and fracture risk.

T-scores and Z-scores provide different forms of comparison, while the wider clinical context helps determine what a result means for an individual.

Bone health is influenced by more than bone mineral density. Nutrition, exercise, smoking, alcohol, medications, medical conditions, falls and previous fractures can all be relevant.

When repeat testing is appropriate, changes should be interpreted with awareness of measurement variability, the timing of the assessment and the individual’s clinical circumstances.

If you are considering a DEXA scan, ask a suitably qualified health professional whether testing is appropriate for your circumstances, what the result can tell you and how it would be considered alongside other information about your bone health.