What Is a DEXA Scan? A Guide to Bone Density Scans
Key takeaways:
The DEXA (dual-energy X-ray absorptiometry) scan is a special X-ray test that looks for bone thinning and loss.
Healthcare professionals recommend DEXA scans for people who are at high risk of developing osteoporosis or fractures.
How often you get a DEXA scan depends on the results of your first test and your overall risk for bone loss.
Table of contents
A DEXA (dual-energy X-ray absorptiometry) scan is a special type of X-ray that measures bone density (strength). In short, it’s a bone density test that measures your bone mass. DEXA scans can be really useful for people at risk for osteoporosis. Osteoporosis is a condition where bones become thinner and weaker. People with osteoporosis are more likely to have bone fractures.
Let’s take a look at how DEXA scans work, why you might need one, and how to prepare if you do.
What is a DEXA scan?
A DEXA scan is a type of imaging test, also called a bone density scan or bone density test. It uses X-rays to measure bone density.
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When you get a DEXA scan, a machine takes X-rays of your lower back, hip, or forearm. The images get processed and the software calculates your bone density.
Your bone density is an important indicator of your overall bone health. A low bone density is a sign of bone thinning and bone loss.
In addition to measuring bone density, DEXA scans can also measure muscle mass and body fat percentage. So a full-body DEXA scan can give a report of body composition.
What is a DEXA scan used for?
The most common reason people get a DEXA scan is to check their bone health. DEXA scans look for:
Bone thinning and weakness (osteopenia)
Bone loss (osteoporosis)
Osteopenia can progress to osteoporosis. And osteoporosis can eventually lead to fractures and other bone problems.
The hope is that people with low bone density can be diagnosed and start treatment early. This can help increase bone density and prevent fractures in the future.
People being treated for osteoporosis also have repeat bone density scanning to monitor how they’re responding to treatment.
Who needs a DEXA scan?
Your healthcare professional may recommend a DEXA scan if you’re at high risk of developing osteopenia or osteoporosis. Some things that increase your risk include:
Age: As you get older, your bones start to lose strength. The DEXA screening guidelines issued by the U.S. Preventive Services Task Force recommends bone density testing for all women over age 65.
Medications: Certain medications like steroids can lead to bone loss.
Medical conditions: People with diabetes and certain liver, kidney, parathyroid, and thyroid conditions can develop osteoporosis.
Hormone changes: Changes in estrogen levels can increase bone loss. This can affect people going through menopause or receiving certain types of gender-affirming care.
Smoking: Smoking is linked to decreased bone density.
Prior bone fractures: Having a history of bone fractures as an adult, especially hip fractures, can be a sign of bone thinning.
Diet and exercise: People who don’t move as much or get enough calcium or vitamin D in their diets are more likely to develop bone loss.
How much does a DEXA scan cost?
The average cost of a DEXA scan is more than $300. But the amount you end up paying depends on your health insurance and the reason the test is being done.
For example, DEXA scans for bone density can be completely covered by Medicare if you’re postmenopausal and older than 65 years. Many insurance companies also cover DEXA scans if you’re at risk for developing osteoporosis.
Check with your health insurer to see what your cost will be. Or you can contact imaging centers directly for a good faith estimate if you plan to pay out of pocket.
What should I expect during a DEXA scan?
A DEXA scan is a routine test that can be done at many imaging centers. The bone density scan procedure is pretty simple. To prepare for your bone density scan, you should:
Stop taking any calcium supplements 24 hours prior to the scan.
Avoid scheduling imaging studies that involve contrast dyes or barium within 2 weeks of the scan.
Make sure you aren’t pregnant, because you’ll need to reschedule if you are.
Stop eating 12 hours before the scan only if you’re having your body composition measured (not just your bone density).
On the day of the test, you’ll be asked to lie on your back on a padded table. The imaging machine, called a C-arm, will pass over your hips and lower back. Your legs will be propped up on a box so that your pelvis and lower back are flat during the test.
When it’s time to look at your hips, you might be asked to turn your foot and leg. Most centers have braces to help you achieve the right position.
The entire process will take about 10 to 15 minutes, and then you’ll be able to go home.
What do my DEXA scan results mean?
Once your DEXA scan is complete, a radiologist will review the results and calculate your bone density.
Your DEXA scan results are reported as a T-score. A T-score compares your bone density test results to the bone density of a 30-year-old adult who doesn’t have low bone density. Here’s how to interpret your T-score:
A T-score that’s -1 or higher is normal.
A T-score between -1 and -2.5 indicates low bone mass or osteopenia.
A T-score less than -2.5 indicates bone loss or osteoporosis.
People with lower T-scores are more likely to develop bone fractures.
How often should I get a DEXA scan?
It depends. People who are at increased risk for bone loss should have a DEXA scan at least once to screen for osteoporosis. After that, how often you need a DEXA scan depends on several factors, such as:
The T-score of your first DEXA scan
Your risk factors for bone loss
Your overall health
This information will determine how often you need a DEXA scan. For example, if your DEXA scan finds osteoporosis (T-score less than -2.5), a DEXA scan may be repeated in 2 years to see how you’re responding to treatment. But if your first DEXA scan is normal and you don’t have many risk factors for bone loss, you may not need to repeat a DEXA for 10 years or more.
The bottom line
A DEXA scan is an accurate way to determine your bone density and body composition. Not everyone needs a DEXA scan. As you get older, you might need one to check your bone health.
A DEXA scan can help you find out if you have osteopenia or osteoporosis, so you can start treatment early, prevent fractures, and keep your bones healthy.
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References
American Bone Health. (2020). Understanding bone density results.
American Family Physician. (n.d.). Don’t routinely repeat dual energy x-ray absorptiometry (DEXA) scans more often than once every two years.
Camacho, P. M., et al. (2020). Postmenopausal osteoporosis guidelines-2020 update. Endocrine Practice.
Endocrine Society. (2012). The Endocrine Society recommends individualization of bone mineral density testing frequency in women over the age of 67.
Kim, J., et al. (2002). Total-body skeletal muscle mass: Estimation by a new dual-energy X-ray absorptiometry method. The American Journal of Clinical Nutrition.
Pouresmaeili, F., et al. (2018). A comprehensive overview on osteoporosis and its risk factors. Therapeutics and Clinical Risk Management.
MedlinePlus. (2021). Bone density scan.
RadiologyInfo.org. (2024). Bone density scan (DEXA or DXA).
Shepherd, J., et al. (2017). Body composition by DXA. Bone.
Siemens Healthineers. (n.d.). Mobile C-arms.
Stevenson, M. O., et al. (2019). Osteoporosis and bone health in transgender persons. Endocrinology and Metabolism Clinics of North America.
University of Alabama at Birmingham. (n.d.). Cost.
U.S. Preventive Services Task Force. (2018). Osteoporosis to prevent fractures: Screening.
Viswanathan, M., et al. (2018). Table 1, recommendations about screening and treatment of osteoporosis from various professional and health organizations. (Evidence Synthesis, No. 162). Screening to Prevent Osteoporotic Fractures: An Evidence Review for the U.S. Preventive Services Task Force.
