Bone health is something most people take for granted — until a fracture, a diagnosis or a routine conversation with a GP brings it into focus. Bone densitometry scanning is the clinical method used to assess bone mineral density (BMD), offering important information about skeletal strength and the risk of conditions such as osteoporosis. This article explains what bone densitometry is, how DXA scanning works, what results may indicate and when discussing this type of assessment with a healthcare professional might be worthwhile.
What Is Bone Densitometry?
Bone densitometry is a method of measuring the mineral content and density of bone tissue. The term "densitometry" simply refers to the measurement of density — in this context, the density of calcium and other minerals within bone.
Bone mineral density (BMD) is used as a marker of bone strength. Healthy bone contains a dense matrix of minerals, particularly calcium and phosphate, which provide structural integrity. As people age, or due to certain medical conditions and lifestyle factors, bone mineral content can gradually decrease. This reduction in BMD makes bones more porous and fragile, increasing the likelihood of fractures — sometimes from minor falls or even everyday movements.
Measuring BMD therefore provides clinically useful information about where an individual's bone health currently stands, and whether further evaluation or management may be appropriate.
What Is a DXA Scan (DEXA Scan)?
The terms DXA and DEXA are used interchangeably and refer to the same procedure. DXA stands for Dual-energy X-ray Absorptiometry, while DEXA is simply an older stylistic variation of the same acronym. Both describe the most widely used method of bone densitometry scanning in clinical practice.
A DXA scan uses two low-dose X-ray beams at different energy levels to measure how much energy is absorbed by bone tissue versus soft tissue. The difference between the two readings allows the scanner to calculate bone mineral density at the site being measured. This is typically the lumbar spine (lower back) and the hip, as these are areas where osteoporosis-related fractures most commonly occur. The forearm may also be scanned in some circumstances.
The radiation exposure from a DXA scan is very low — considerably lower than that of a standard chest X-ray — making it a well-tolerated and widely used assessment tool.
It is important to understand that DXA scanning is specifically designed to measure bone mineral density. It is not the same as other types of bone imaging, and this distinction is covered in more detail below.
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Why Is Bone Density Testing Used?
Bone density testing is used to assess bone health and to identify whether bone mineral density has fallen to a level associated with increased fracture risk. The principal clinical application is in the assessment and management of osteoporosis — a condition characterised by reduced bone density and deterioration of bone microstructure.
Osteoporosis is often described as a "silent" condition because bone loss typically occurs without symptoms. Many people are unaware they have reduced bone density until a fracture occurs. A bone density scan offers a way to identify low BMD before a fracture happens, enabling appropriate clinical decisions to be made.
Bone densitometry may also be used to:
The decision to refer someone for bone densitometry is a clinical one, and the appropriateness of testing depends on individual circumstances, medical history and risk factors.
Who May Need a Bone Density Scan?
Healthcare professionals use a range of clinical tools and risk assessment frameworks to identify individuals who may benefit from bone density evaluation. In the UK, tools such as FRAX® (developed by the University of Sheffield) and QFracture® are commonly used to estimate fracture risk before or alongside bone densitometry.
A healthcare professional may consider a bone density scan appropriate for:
This list reflects common clinical scenarios and is not exhaustive. Whether a scan is recommended depends on a thorough individual assessment by a qualified healthcare professional. It is not appropriate to self-diagnose based on the presence or absence of risk factors.
What Happens During a Bone Density Scan?
A DXA scan is a straightforward, non-invasive procedure that is generally quick and comfortable. Here is what patients can typically expect:
Before the Scan
Preparation requirements are minimal for most people. In general:
Women who are pregnant, or who think they may be pregnant, should inform the clinical team before the scan.
During the Scan
The procedure itself is painless and does not involve entering a tunnel or enclosed space. The patient lies flat on a padded scanning table. A mechanical arm passes slowly over the body, emitting low-dose X-ray beams to measure the density of bone at the targeted sites. The hip and lumbar spine are the most commonly assessed areas.
A standard DXA scan typically takes between 10 and 30 minutes in total, depending on the number of sites measured. No injections or contrast agents are used.
After the Scan
There is no recovery time following a DXA scan. Patients can return to their normal activities immediately. Results are typically reviewed and reported by a radiologist or other appropriately qualified clinician, and are then discussed with the referring healthcare professional.
Bone Density Scan Results: What They May Indicate
Bone density scan results are reported numerically and expressed in a standardised way to allow meaningful clinical interpretation.
T-Scores
The T-score is the most commonly referenced figure in bone densitometry results for adults aged 50 and over (and postmenopausal women). It compares an individual's bone mineral density to that of a young adult reference population of the same sex at peak bone mass.
According to guidance from the World Health Organisation (WHO), T-score categories are broadly understood as:
It is important to emphasise that T-scores must be interpreted within the full clinical context — including age, sex, medical history, fracture history and other risk factors. A T-score alone does not determine an individual's overall fracture risk or dictate management.
Z-Scores
The Z-score compares bone density to what would be expected in a person of the same age, sex and body size. Z-scores are more commonly used in premenopausal women, men under 50 and children, where comparing to age-matched peers provides more clinically relevant information than comparing to peak bone mass.
A significantly low Z-score may prompt investigation into secondary causes of bone loss.
Results in Context
Bone density scan results should always be reviewed and explained by a healthcare professional with knowledge of the individual's overall health. The results of a DXA scan inform — but do not replace — comprehensive clinical assessment. Treatment decisions, follow-up arrangements and lifestyle recommendations should be discussed with an appropriate clinician.
Bone Densitometry vs Other Bone Scans
It is a common source of confusion that the term "bone scan" can refer to different types of imaging. These are not interchangeable, and it is important to understand the distinction.
DXA / Bone Densitometry
As described throughout this article, a DXA scan measures bone mineral density. Its primary purpose is to assess bone strength and identify low BMD associated with osteoporosis. It uses low-dose dual-energy X-rays and is performed as an outpatient procedure with no preparation beyond the minor points noted above.
Nuclear Medicine Bone Scan
A nuclear medicine bone scan (sometimes simply called a "bone scan" in a hospital setting) is an entirely different procedure. It involves the injection of a small amount of radioactive tracer into the bloodstream. Areas of abnormal bone activity — such as those associated with cancer spread (metastases), infection, inflammation or certain fractures — absorb the tracer at a different rate and show up on the scan images.
A nuclear medicine bone scan does not measure bone mineral density and is not used to diagnose osteoporosis. The two procedures are distinct in their purpose, methodology and clinical application.
X-rays and CT Scans
Standard X-rays can sometimes reveal the presence of a fracture or suggest reduced bone density in advanced cases, but they are not sensitive enough to quantify BMD accurately. CT scanning can provide detailed bone images but is not the standard method for routine BMD measurement due to higher radiation exposure and cost.
DXA scanning is widely used for bone mineral density assessment in routine clinical contexts in the UK, in line with current national guidance.
Osteoporosis and Bone Density
Osteoporosis is a skeletal condition in which bones become less dense and structurally compromised, making them more susceptible to fracture. It is estimated to affect millions of people in the UK, with many cases undiagnosed until a fracture occurs.
Bone mineral density is one of the key factors associated with fracture risk in osteoporosis, though it is not the only one. The underlying architecture of bone tissue, rate of bone turnover, and additional clinical risk factors all contribute to overall skeletal fragility.
The relationship between bone density and osteoporosis is well established, and DXA scanning plays a central role in osteoporosis assessment pathways in the UK. Guidance from NICE (National Institute for Health and Care Excellence) and the Royal Osteoporosis Society informs clinical practice around when and how bone densitometry should be used.
If you are concerned about your bone health, the most appropriate step is to speak with your GP or a relevant specialist, who can assess whether a bone density scan or other evaluation is indicated for your individual circumstances.
After the Scan: Next Steps
Receiving the results of a bone density scan is not an endpoint in itself — it is the beginning of a clinical conversation. Once results have been reported and reviewed:
Bone health is influenced by multiple factors, and a DXA scan is one piece of the broader clinical picture. Regular monitoring may be recommended depending on initial results and clinical circumstances.
Supporting Your Overall Health
While bone densitometry scanning is a specialist imaging procedure, general health screening and blood testing play a complementary role in understanding your overall wellbeing. Blood tests can help identify certain conditions — such as vitamin D deficiency, thyroid dysfunction or inflammatory markers — that may have implications for bone health.
If you are interested in understanding your general health through private blood testing, Private Blood Tests London offers a range of clinically relevant tests, including thyroid testing, full blood count testing and health screening packages. You can review indicative blood test prices or book a test at your convenience. Please note that final prices may vary and a full breakdown of costs will be confirmed prior to or at the time of booking.
Please note that private blood tests are not a substitute for bone densitometry scanning or for clinical assessment by a healthcare professional. If you have specific concerns about your bone health, speak with your GP in the first instance.
Frequently Asked Questions
What is bone densitometry?
Bone densitometry is a method of measuring the mineral content and density of bone. It is used to assess bone strength and identify whether bone mineral density has fallen to a level associated with conditions such as osteoporosis.
What does a bone density scan measure?
A bone density scan measures bone mineral density (BMD) — the amount of mineral, primarily calcium, contained within a given volume of bone tissue. This provides an indication of bone strength and fracture risk.
Is a DXA scan the same as a DEXA scan?
Yes. DXA (Dual-energy X-ray Absorptiometry) and DEXA are different abbreviations for the same procedure. The terms are used interchangeably in clinical and everyday contexts.
How does a DXA scan work?
A DXA scanner emits two low-dose X-ray beams at different energy levels. By measuring how much energy is absorbed by bone compared to surrounding soft tissue, the scanner calculates bone mineral density at the targeted sites — usually the hip and lumbar spine.
Is a bone density scan the same as a bone scan?
No. A bone density scan (DXA scan) measures bone mineral density and is used to assess osteoporosis risk. A nuclear medicine bone scan uses a radioactive tracer to detect areas of abnormal bone activity such as metastases or infection. These are entirely different procedures with different clinical purposes.
Can a bone density scan detect osteoporosis?
A DXA scan can identify low bone mineral density consistent with osteoporosis or osteopenia. However, results must always be interpreted by a qualified healthcare professional in the context of full clinical information, including medical history and other risk factors.
What do T-scores mean in bone density scan results?
A T-score compares your bone mineral density to that of a young adult at peak bone mass. A T-score of -1.0 or above is generally considered normal; between -1.0 and -2.5 indicates low bone density (osteopenia); and -2.5 or below is consistent with osteoporosis. T-scores must be interpreted alongside clinical context.
What is the difference between a T-score and a Z-score?
A T-score compares your BMD to a young adult reference population, whereas a Z-score compares it to age-matched peers. Z-scores are typically used for younger adults, premenopausal women, men under 50 and children, where age-matched comparison is more clinically informative.
Who should consider a bone density test?
Healthcare professionals may recommend a bone density test for postmenopausal women, individuals over 50 who have had a fragility fracture, people with conditions affecting bone health, those on long-term corticosteroid therapy and others identified as being at higher risk of osteoporosis. The decision is made individually by a clinician.
Is a bone density scan painful or dangerous?
A DXA scan is non-invasive and painless. The radiation dose is very low — significantly less than that of a standard chest X-ray — and is not considered clinically significant for most patients.
How long does a bone density scan take?
A DXA scan typically takes between 10 and 30 minutes, depending on the number of sites being assessed. No recovery time is needed, and patients can return to normal activities immediately afterwards.
What should I do if my bone density scan results show low BMD?
If your results indicate low bone mineral density, discuss the findings with the healthcare professional who arranged or reviewed your scan. They can advise on whether further investigation is needed, explain what the results mean for your individual situation and discuss any appropriate next steps, which may include lifestyle guidance or further clinical assessment.
This article is intended for general informational purposes only. It does not constitute medical advice and should not be used as a substitute for professional clinical assessment. If you have concerns about your bone health, please consult a qualified healthcare professional. Private Blood Tests London offers private blood testing services; bone densitometry scanning is a specialist imaging procedure that should be arranged through an appropriate clinical referral pathway.