Everything You Need to Know About DEXA Scans and Bone Density Testing

If you are concerned about your bone health — or if your doctor has suggested you might be at risk of osteoporosis — the most important diagnostic tool available to you is the DEXA scan. Short for dual-energy X-ray absorptiometry (sometimes written as DXA scan), this simple test measures your bone mineral density and provides the clearest picture available of your bone health. Understanding how it works, who needs one, and how to interpret the results can take a lot of the uncertainty out of managing your bone health.

What Is a DEXA Scan?

A DEXA scan is a specialized type of low-dose X-ray that measures bone mineral density — how much calcium and other minerals are packed into your bone tissue. It is the gold-standard test for diagnosing osteoporosis and osteopenia, and is used to monitor changes in bone density over time and to assess fracture risk.

The scan is most commonly performed on the lumbar spine (lower back) and hip, as these are the sites most prone to osteoporotic fractures. Occasionally the forearm is also measured. The test takes approximately 10 to 20 minutes, involves no injections or invasive procedures, and uses a very low level of radiation — significantly less than a standard chest X-ray.

What Happens During a DEXA Scan?

You will be asked to lie on a padded table, usually fully clothed (though you may be asked to remove items with metal such as belts or jewellery). A scanning arm will pass slowly over your body while a detector measures how much energy from two low-dose X-ray beams is absorbed by your bones compared to soft tissue. The denser your bone, the more energy is absorbed, and the higher your bone mineral density score.

The procedure is completely painless. You do not need to fast beforehand, though you should avoid taking calcium supplements on the day of the scan, as these can slightly skew results.

Who Should Have a Bone Density Test?

Osteoporosis screening guidelines recommend DEXA scanning for all women aged 65 and over, and for men aged 70 and over. However, testing is also recommended at younger ages for anyone with significant risk factors. You should discuss bone density testing with your doctor if you are a woman aged 50 to 64 who has experienced menopause or has other risk factors; a man aged 50 to 69 with risk factors such as low testosterone, smoking, or long-term steroid use; someone of any age who has experienced a fragility fracture; a person using long-term corticosteroids or other bone-affecting medications; or someone with a health condition known to affect bone density.

Understanding Your DEXA Scan Results

Your results will include a T-score, which compares your bone density to that of a healthy 30-year-old of the same sex. A T-score of -1.0 or higher is considered normal. A score between -1.0 and -2.5 indicates osteopenia (lower than average bone density). A score of -2.5 or lower indicates osteoporosis. Each full point below zero represents approximately a 10–12% reduction in bone density and roughly doubles your fracture risk.

You may also see a Z-score, which compares your bone density to others of your own age and sex. A Z-score significantly below average may suggest a secondary cause for your bone loss that warrants investigation.

How Often Should You Have a DEXA Scan?

If your results are normal and you have no significant risk factors, repeat scanning every three to five years may be sufficient. If you have osteopenia or osteoporosis, or are on treatment, your doctor will typically recommend a repeat scan every one to two years to monitor changes in bone density and assess whether treatment is working. Major changes in health, medication, or fracture history may also prompt an earlier scan.

Preparing for Your Appointment

Getting a bone density test is straightforward. Your GP can refer you for a DEXA scan based on your age and risk factors. In some areas, dedicated bone health clinics or osteoporosis services offer comprehensive assessment alongside scanning. When attending your appointment, wear comfortable clothing without metal fasteners, skip your calcium supplement that morning, and bring a list of any medications you take, as some affect bone density.

Frequently Asked Questions

Is a DEXA scan the same as a regular X-ray? No. Regular X-rays can detect fractures but are not sensitive enough to diagnose osteoporosis until bone density is very low. A DEXA scan is specifically designed to measure bone mineral density with much greater precision.

Can I have a DEXA scan if I am pregnant? DEXA scanning is not recommended during pregnancy due to the X-ray component. If you have significant bone health concerns during pregnancy, discuss alternative monitoring approaches with your doctor.

Does Medicare or private health insurance cover DEXA scans? Coverage varies by country and insurer. In many countries, DEXA scans are covered for people who meet certain age and risk-factor criteria. Check with your GP or health insurer for details relevant to your situation.