A bone density test takes about 5 to 10 minutes of actual scanning time. The full appointment, including check-in and positioning, typically runs around 30 minutes. It’s one of the fastest and simplest imaging tests you can get.
What Happens During the Scan
The most common type of bone density test is called a DEXA scan (sometimes written DXA). You lie flat on a padded table while a scanning arm passes over your body, measuring bone density at the hip and lower spine. You don’t need to hold your breath or stay perfectly still the way you might for an MRI. The machine uses two low-energy X-ray beams to distinguish bone from soft tissue, and the whole process is painless.
The scan itself takes 5 to 10 minutes for a central DEXA, which measures the hip and spine. Peripheral scans, which check smaller bones like the wrist or heel, take even less time, often just a few minutes. Peripheral devices are sometimes found at pharmacies or health fairs as screening tools, but they’re less reliable for diagnosing osteoporosis than a full hip and spine scan.
Why the Appointment Takes Longer
Plan for about 30 minutes total at the imaging center. The extra time covers paperwork, changing clothes if needed, and getting positioned correctly on the table. A technologist will make sure your body is aligned properly, which matters for accurate results. If you’ve had a previous scan, consistent positioning also helps your doctor compare measurements over time.
How to Prepare
Preparation is minimal. The Mayo Clinic advises skipping calcium supplements for at least 24 hours before the test, since undigested calcium in your system can interfere with readings. You can eat and drink normally otherwise.
Wear loose, comfortable clothing without metal zippers, belt buckles, or snaps. Metal can distort the X-ray image. You’ll also want to remove any jewelry near the scan area. Some facilities provide a gown, but if you wear simple athletic clothes, you may not need to change at all.
If you’ve had a barium study or received contrast dye for a CT scan recently, let the scheduling office know. Residual contrast material can affect accuracy, so the center may ask you to wait a week or two before your DEXA.
Radiation Exposure Is Extremely Low
A DEXA scan delivers between 0.001 and 0.01 millisieverts of radiation, according to the Australian Radiation Protection and Nuclear Safety Agency. To put that in perspective, a standard chest X-ray delivers roughly 0.02 millisieverts, so a bone density scan exposes you to less radiation than a single chest X-ray. You receive more radiation during a cross-country flight from natural cosmic rays than you do from this test.
When Results Come Back
Your results are reported as a T-score, which compares your bone density to that of a healthy 30-year-old adult. The scale works like this:
- T-score of -1.0 or above: Normal bone density
- T-score between -1.0 and -2.5: Low bone mass, called osteopenia
- T-score of -2.5 or below: Osteoporosis
Most imaging centers send results to your referring doctor within a few business days. Some facilities offer preliminary results the same day, but the formal report requires a radiologist’s review. Your doctor will then discuss the findings and whether any follow-up is needed.
Who Should Get Tested
The U.S. Preventive Services Task Force recommends routine bone density screening for all women 65 and older. Postmenopausal women younger than 65 should also be screened if they have risk factors like low body weight, a parent who fractured a hip, smoking, or heavy alcohol use. For men, there isn’t yet enough evidence to make a blanket screening recommendation, though doctors often order the test for men with specific risk factors like long-term steroid use or low testosterone.
If your first scan shows normal bone density, you likely won’t need another one for several years. People with osteopenia or osteoporosis are typically rescanned every one to two years to track changes and gauge whether treatment is working.