Bone density scan (DEXA): what it shows, results, and next steps
Last updated September 6, 2026.
A bone density scan, called DEXA or DXA, is a quick low-dose X-ray test that measures how much mineral is packed into your bones, usually at the hip and lower spine. It is not a treatment in itself. It gives your clinician a number, the T-score, that sorts your bones into normal, low bone mass (osteopenia), or osteoporosis, and that number guides whether you need calcium and vitamin D, exercise and fall-proofing, or a prescription bone medicine. What changes urgency is not the scan result by itself but a fracture: sudden severe back pain, a broken bone after a minor fall, or inability to stand on a leg needs care right away, not a scheduled scan.
What are the symptoms of Bone density scan (DEXA)?
- Low bone density usually causes no symptoms at all until a bone breaks
- A broken wrist, hip, or rib from a minor fall or a low-height fall
- Sudden sharp back pain with no clear injury, which can be a spine compression fracture
- Losing height, often more than an inch and a half from your tallest adult height
- A rounded upper back or stooped posture that is new
- Ongoing back pain that eases when you lie down
- Age 65 and older for women, 70 and older for men, or earlier with steroid use, early menopause, or a parent who broke a hip
Bone pain that is constant, wakes you at night, comes with fever or unexplained weight loss, or is centered on one spot points away from simple low bone density and toward infection, inflammation, or another cause that needs its own workup.
How does a doctor diagnose Bone density scan (DEXA)?
The decision to order a DEXA comes from your history more than your exam. Your clinician asks your age and menopause status, whether you have broken any bone as an adult after a simple fall, whether a parent broke a hip, and about smoking, alcohol intake, body weight, and medicines such as prednisone, aromatase inhibitors, or long-term proton pump inhibitors. Conditions like rheumatoid arthritis, celiac disease, hyperthyroidism, and chronic kidney disease raise the odds enough to scan earlier. Many clinicians run a FRAX fracture risk estimate to decide whether scanning changes anything. The scan itself takes about 10 to 30 minutes, you stay dressed in most cases, and the radiation dose is a small fraction of a chest X-ray. Results come back as a T-score comparing you to a healthy young adult: above minus 1.0 is normal, minus 1.0 to minus 2.5 is low bone mass, and minus 2.5 or lower meets the definition of osteoporosis. For premenopausal women, men under 50, and children, the Z-score is used instead, and a low Z-score prompts blood tests for vitamin D, calcium, thyroid, kidney function, and celiac disease to look for a secondary cause.
How is Bone density scan (DEXA) treated?
- Calcium and vitamin D: Most adults are advised to get roughly 1,000 to 1,200 mg of calcium a day, food first, and 600 to 800 IU of vitamin D, with higher doses if a blood test shows you are low. This is the base layer under every other treatment, not a substitute for one.
- Exercise and fall prevention: Weight-bearing activity such as walking, stair climbing, or dancing plus resistance training two or three days a week helps maintain bone and muscle. Balance work, a home check for loose rugs and poor lighting, a vision check, and a review of medicines that cause dizziness cut fracture risk directly.
- Bisphosphonates, first-line prescription: Alendronate and risedronate are taken weekly or monthly by mouth on an empty stomach with a full glass of water, staying upright for 30 to 60 minutes. Zoledronic acid is a once-yearly IV option if pills upset your stomach or you have reflux. Most people are reassessed after 3 to 5 years to decide on a break from treatment.
- Other prescription options: Denosumab is an injection every 6 months and must not be stopped without a replacement drug because bone loss rebounds quickly. For very high risk or a recent fracture, bone-building drugs such as teriparatide, abaloparatide, or romosozumab are used for a limited course and then followed by a bisphosphonate to hold the gains.
- Repeat scanning: A follow-up DEXA is typically done about 2 years after starting treatment, sometimes sooner on steroids and often longer if your first scan was normal. Compare scans on the same machine when you can, since results from different machines are not directly interchangeable.
When is Bone density scan (DEXA) an emergency?
The scan is never the emergency; a fracture can be. Call 911 for sudden back pain with numbness or weakness in your legs, loss of bladder or bowel control, or numbness around the groin, which can mean a collapsed vertebra pressing on the spinal cord. Also call 911 after a fall if your hip or thigh hurts and you cannot stand or bear weight, if a leg looks shortened or turned outward, or if you hit your head and are on a blood thinner. Go to the ER for a visibly deformed or open fracture, severe pain after any fall, or new severe back pain that came on in seconds while lifting or coughing. Urgent care fits a suspected wrist, ankle, or rib fracture where you can walk and are stable, since they can X-ray and splint. Same-day, non-emergency contact with your clinician is right if you have lost more than an inch and a half of height, have new back pain that has lasted more than a few days, or are on denosumab and have missed a dose past its due date.
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Common questions
Does a DEXA scan hurt, and how much radiation is involved?
It does not hurt. You lie on a padded table, a scanner arm passes over your hip and lower spine, and you hold still for a few minutes. There is no injection, no dye, and no enclosed tube, so it does not trigger claustrophobia the way an MRI can. The radiation dose is very low, a small fraction of what a chest X-ray delivers and less than a day of ordinary background radiation. Tell the technologist if you are or might be pregnant, and mention any recent barium study or contrast scan, since those can distort the images and usually mean waiting a week or two.
What do my T-score and Z-score actually mean?
The T-score compares your bone density to that of a healthy young adult at peak bone mass. Above minus 1.0 is normal, minus 1.0 to minus 2.5 is low bone mass or osteopenia, and minus 2.5 or lower meets the definition of osteoporosis. Each full point down roughly doubles fracture risk, which is why a small change in the number matters. The Z-score compares you to people your own age and sex, and it is the one used for premenopausal women, men under 50, and children. A Z-score of minus 2.0 or lower is called below the expected range for age and prompts a search for an underlying cause such as low vitamin D, thyroid disease, celiac disease, or a medicine effect.
I have osteopenia, not osteoporosis. Do I need medicine?
Often no, but not always. Many people with a T-score between minus 1.0 and minus 2.5 do well with calcium, vitamin D, weight-bearing and resistance exercise, stopping smoking, limiting alcohol, and fall-proofing the home. Your clinician will usually run your numbers through the FRAX tool, which combines your T-score with age, weight, fracture history, family history, steroid use, and other factors to estimate your 10 year fracture risk. In the US, treatment is commonly recommended when that risk is about 3 percent or higher for hip fracture or 20 percent or higher for major osteoporotic fracture. A past fragility fracture or ongoing prednisone use can move you to treatment regardless of where the T-score lands.
How often should I repeat the scan?
It depends on the first result and what you are doing about it. If your baseline scan is normal or only mildly low and you have no major risk factors, a repeat in about 5 to 10 years is often reasonable, since bone changes slowly. If you are starting or on treatment, most clinicians repeat at about 2 years to confirm you are stable or improving. People on long-term steroids, or those who have had a new fracture or a big change in medicines, may be scanned sooner. Try to use the same facility and machine each time, because small calibration differences between machines can look like real change when they are not.
Can I eat or take my supplements before the scan?
You can eat normally and take your usual medicines. Skip calcium supplements for about 24 hours before the appointment, since undissolved tablets in your abdomen can sit over the spine and falsely raise the reading. Wear clothes without zippers, snaps, metal buttons, or underwire, and leave jewelry at home so you can stay dressed. Let the staff know about any metal hardware, spinal fusion, or hip replacement, because those areas get excluded from the measurement. Also mention if you have had a recent CT with contrast, a nuclear medicine test, or a barium swallow.
Is a heel ultrasound or the scan at the pharmacy the same thing?
No. Portable heel, finger, or wrist ultrasound devices are screening tools that can flag people who may need further testing, but they do not measure the hip and spine, which are the sites that predict serious fractures. Osteoporosis is formally diagnosed on a central DEXA of the hip and lumbar spine, and treatment decisions and follow-up are based on that test. If a screening device gives you a low reading, the next step is a central DEXA, not a prescription. If your central scan is being used to track treatment, only central DEXA results can be meaningfully compared over time.
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