A DEXA scan (also called a DXA scan) is a quick, painless test that uses a very small amount of X-ray radiation to measure how dense your bones are. It usually checks the hip and lower spine. The result helps a healthcare professional assess whether bone density is low, estimate fracture risk, and decide whether further evaluation or treatment may be helpful.
What Does a DEXA Scan Measure?
DEXA stands for dual-energy X-ray absorptiometry. It measures bone mineral density (BMD), which describes how much mineral is present in a specific area of bone. This information helps assess bone strength and identify low bone density before a fracture occurs.
According to RadiologyInfo, DEXA is the standard imaging method used to measure bone mineral density and is commonly performed on the lumbar spine and hip. These areas are particularly important when assessing osteoporosis and the risk of fractures. The scan can also help healthcare professionals monitor changes in bone density during osteoporosis treatment.
Osteoporosis causes bones to become less dense and more fragile, increasing the likelihood of fractures. The condition may develop without noticeable symptoms, so a person can have bone loss without knowing it. A DEXA scan provides objective measurements that help identify this problem and guide decisions about further assessment.
Who Should Have a DEXA Scan for Osteoporosis?
The need for a DEXA scan depends on age, menopausal status, medical history, previous fractures, medications, and other factors that affect bone health. The US Preventive Services Task Force recommends osteoporosis screening for women aged 65 years and older, as well as postmenopausal women younger than 65 who are at increased risk based on clinical risk assessment.
Recommendations for men vary. The US Preventive Services Task Force considers the evidence insufficient to determine the overall benefits and harms of routine screening for osteoporosis in men. However, the International Society for Clinical Densitometry includes men aged 70 and older, along with younger men who have relevant risk factors, among those for whom bone density testing may be indicated. Testing may also be appropriate for people of any sex with known risk factors or suspected bone loss.
A healthcare professional may recommend a DEXA scan in situations such as:
- Being in an age group for which osteoporosis screening is recommended.
- Having a fracture after a minor fall or relatively small injury.
- Having a low body weight or a family history of hip fracture.
- Having a medical condition associated with bone loss.
- Taking medicines that can weaken bones, particularly with long-term use of certain corticosteroids.
- Needing a baseline bone density measurement before treatment or follow-up testing to assess changes over time.
These factors do not automatically mean that someone has osteoporosis. They help a healthcare professional decide whether testing is likely to be useful. Screening recommendations can differ between countries and professional guidelines, so the appropriate timing should be based on the person's circumstances and local clinical guidance.
How Should You Prepare for a DEXA Scan?
Most people need little preparation before a DEXA scan. According to Mayo Clinic, the test generally does not require fasting, and people can usually continue eating normally. However, you should avoid calcium supplements for 24 hours before the examination unless your healthcare professional or imaging center gives different instructions.
For a smoother appointment, follow these practical steps:
- Wear comfortable clothing without metal zippers, buttons, or belts near the areas being scanned.
- Remove jewelry and other metal objects that could interfere with the images.
- Tell the imaging team if you have recently undergone an examination involving barium or received contrast material for certain CT or nuclear medicine scans. These substances may interfere with the test, and the team can advise whether it needs to be postponed.
- Inform the healthcare professional if you are pregnant or think you could be pregnant, because the examination uses X-rays.
- Bring your previous bone density reports if available, particularly if this is a repeat examination.
What Happens During a DEXA Scan?
A DEXA scan is usually performed at a hospital or diagnostic imaging center on an outpatient basis. You lie on a padded examination table while the machine scans the relevant areas of your body. For a spine measurement, your legs may be positioned on a support. For a hip measurement, your foot may be placed in a holder to keep the hip in the correct position.
The scanning arm moves over your body and uses low-dose X-rays to measure bone density. You will need to remain still while the images are taken. The examination is painless, and there are no needles or injections involved. You can generally return to your usual activities immediately afterward.
The scan commonly takes about 10 to 30 minutes, depending on the equipment and the areas being examined. The actual scanning time may be shorter, although the entire appointment can take longer. The radiation exposure is very low compared with many other X-ray examinations.
How Are DEXA Scan Results Interpreted?
The report usually includes a T-score and may include a Z-score. These scores compare your bone density with a reference group. Which score is most useful depends on your age and reproductive or hormonal status, so the same numerical result may need different interpretation in different people.
What Does the T-Score Mean?
For postmenopausal women and men aged 50 years and older, the T-score is commonly used to classify bone density. It compares the measured bone density with that of a healthy young adult reference group. A lower, more negative score indicates lower bone mineral density.
Under the commonly used World Health Organization classification, T-score ranges are interpreted as follows:
- Normal bone density: A T-score of -1.0 or higher.
- Low bone mass, also called osteopenia: A T-score below -1.0 but above -2.5.
- Osteoporosis: A T-score of -2.5 or lower at an appropriate diagnostic site, such as the lumbar spine, total hip, or femoral neck.
These categories are based on bone density measurements and are not a complete assessment of future fracture risk. A healthcare professional must consider the scan's measurement sites, the quality of the images, previous results, and relevant clinical factors before determining what the findings mean for an individual.
What Is the Difference Between a T-Score and a Z-Score?
A Z-score compares your bone density with that of people of a similar age and sex. It is generally preferred when interpreting bone density in women before menopause and men younger than 50 years. A Z-score of -2.0 or lower is described as below the expected range for age. It does not, by itself, establish a diagnosis of osteoporosis.
Children and younger adults require age-appropriate interpretation, and the standard T-score categories should not be applied to everyone. In particular, bone density alone cannot establish osteoporosis in men younger than 50 years. Your healthcare professional will interpret the report according to the relevant clinical standards.
What Can a DEXA Scan Tell You—and What Are Its Limits?
A DEXA scan can identify low bone density, help support the diagnosis of osteoporosis in appropriate patients, and contribute to an assessment of fracture risk. It can also provide a baseline for monitoring bone density when treatment or changes in risk factors make follow-up testing useful.
However, bone density is only one part of fracture risk. As MedlinePlus explains, bone density testing helps estimate the likelihood of future fractures, but it cannot predict with certainty whether a person will break a bone. Previous fractures, age, falls, medicines, and other clinical factors can also affect risk.
The test also cannot identify every cause of low bone density. If the results are unexpected or suggest that additional evaluation is needed, a healthcare professional may review your medical history, medicines, and other health information and may order further tests.
What Happens After the DEXA Scan?
A radiologist or another appropriately trained healthcare professional interprets the measurements and prepares a report. The referring clinician then explains the findings in the context of your fracture risk and medical history.
If the results show normal bone density, the clinician may recommend future screening according to your age and risk factors. If they indicate low bone mass or osteoporosis, the next steps depend on the degree of bone loss, overall fracture risk, previous fractures, and other health considerations. Recommendations may include addressing contributing factors, reviewing medicines, or discussing treatments intended to reduce fracture risk.
Repeat scans are not needed at the same interval for everyone. The timing depends on the initial results, changes in health or treatment, and whether another measurement is likely to affect care. A repeat DEXA scan should have a clear clinical purpose rather than being performed automatically every year.
Discuss the report with your healthcare professional before making decisions about treatment or repeat testing. Understanding both the bone density measurement and your overall fracture risk helps ensure that the results are used appropriately.