How Long Is a Bone Density Test? What to Expect

A standard bone density test using central DEXA (dual-energy X-ray absorptiometry) takes roughly 10 to 30 minutes from the moment you lie down to the moment you get up. The scan itself, where the machine’s arm passes over your body, often runs closer to 10 to 15 minutes, with the rest of the visit consumed by paperwork, positioning, and changing clothes. The experience is painless, requires no injections or fasting, and involves far less radiation than a standard chest X-ray. But the type of bone density test you’re getting, and the sites being scanned, can shift that timeline noticeably.

What Happens During a Central DEXA Scan

Central DEXA is the gold standard for measuring bone mineral density, and it’s the version your doctor is almost certainly referring to when they order a bone density test. You’ll be asked to lie flat on a padded table while a scanning arm passes slowly above you, usually imaging the lower spine and one hip. Some clinics also scan the forearm in the same session, which adds a couple of minutes.

You stay fully clothed for most DEXA scans, though you may need to change into a gown if you’re wearing anything with metal zippers, buttons, or underwire. Belts, jewelry near the scan area, and even certain fabrics with metallic threads can interfere with the image. The technologist will position you carefully, sometimes placing a foam block under your knees or rotating your feet inward to get a clear view of the hip. That positioning step matters: even a slight shift can change the reading, so expect the tech to take a minute to get everything just right.

Once the scan starts, all you do is lie still and breathe normally. There’s no tunnel or enclosed space, so claustrophobia isn’t a factor. The machine doesn’t touch you, and there’s no noise beyond a quiet hum. Most people describe it as one of the easiest medical tests they’ve had.

Peripheral Tests Are Faster but More Limited

Not every bone density test involves lying on a table. Peripheral devices scan sites like the heel, wrist, or finger, and they can be done in a minute or two. You might encounter a heel ultrasound device at a health fair or pharmacy screening event. These portable units measure bone quality using sound waves rather than X-rays, and they’re quick and completely radiation-free.

The trade-off is precision. Heel ultrasound can flag people who may be at risk, but the criteria for diagnosing osteoporosis from ultrasound alone aren’t well established, and the technique can’t reliably track changes in bone mass over time because of limited precision and the slow rate of change at peripheral skeletal sites. Most people with a concerning ultrasound result will still need a central DEXA to confirm the diagnosis and serve as a baseline for monitoring treatment.¹

Peripheral DEXA (pDXA) scanners, which image the forearm or heel using X-rays, offer a middle ground. They’re faster than central DEXA and have been shown to correlate reasonably well with spine and hip measurements, with one evaluation finding a correlation of about 0.63 between forearm bone density z-scores and lumbar spine z-scores, and about 0.72 with the neck of the femur.² Those correlations are decent but not perfect, which is why central DEXA of the hip and spine remains the reference method when treatment decisions are on the line. Peripheral devices have the advantage of rapid patient throughput, so if you’re getting a wrist or forearm scan, expect to be in and out within just a few minutes.

How to Prepare for Your Appointment

Preparation for a central DEXA is minimal, which is one reason the test is so straightforward. There’s no fasting required and no need to stop medications beforehand, with one exception: if you’ve recently had a barium study or been injected with contrast dye for a CT scan or MRI, your doctor may ask you to wait a week or two before scheduling the DEXA, because residual contrast material can artificially inflate the readings.

Calcium supplements are worth pausing on the day of your scan. Taking a calcium pill shortly before the test won’t change your bone density in any meaningful way, but undigested calcium sitting in your gut can sometimes show up on the spine image and skew the numbers. Many clinics advise skipping your calcium supplement the morning of the test just to be safe.

Wear comfortable, loose-fitting clothes without metal. Athletic wear or scrub-style pants and a plain T-shirt work well. If you forget and show up in jeans with a metal zipper, you’ll probably just be asked to change into a gown, which adds a few minutes to the visit but isn’t a big deal.

What Your Results Mean

Your bone density results come back as a T-score, which compares your bone mineral density to that of a healthy young adult at peak bone mass. A T-score of −1.0 or above is considered normal. Between −1.0 and −2.5 is classified as low bone mass (sometimes called osteopenia). A T-score of −2.5 or below indicates osteoporosis. These thresholds were established by the World Health Organization and remain the standard used worldwide.

The practical weight of those numbers is substantial. Research comparing fracture risk across these categories found that at age 50, people with osteoporosis-range T-scores had roughly six to seven times the risk of hip fracture compared with those who did not have osteoporosis.³ That same study found the prevalence of osteoporosis among women aged 50 to 84 was about 21%, compared with roughly 6% in men of the same age range. Those numbers help explain why screening guidelines lean so heavily toward women.

Results are usually available within a day or two, and many clinics will call you only if something needs attention. If your T-score is in the osteopenia range, your doctor may discuss lifestyle changes, calcium and vitamin D intake, and when to retest. If it’s in the osteoporosis range, you’ll likely talk about medication options and fall prevention.

Who Should Get Tested and When

The US Preventive Services Task Force recommends routine bone density screening for all women aged 65 and older to prevent osteoporotic fractures. For postmenopausal women younger than 65, screening is recommended if they have one or more risk factors for osteoporosis, as estimated by a clinical risk assessment tool.⁴ For men, the current evidence is considered insufficient to make a blanket screening recommendation, though individual doctors may order the test based on risk factors like long-term steroid use, low body weight, or a history of fractures.

Risk factors that have been identified as particularly relevant include being 61 or older, weighing 165 pounds or less, and never having used estrogen therapy (either oral contraceptives or hormone replacement).⁵ Other triggers that commonly prompt a test include a fragility fracture (breaking a bone from a fall at standing height or less), a family history of hip fracture, smoking, heavy alcohol use, and certain medical conditions like rheumatoid arthritis or hyperthyroidism.

If your initial DEXA is normal, a repeat scan every two to three years is a common follow-up schedule, though some providers stretch that interval to five years for people with solidly normal readings. If you’re on osteoporosis medication, your doctor may want to recheck sooner to see whether treatment is working.

How Much Radiation Are You Getting?

One of the most common worries about DEXA is radiation, but the exposure is genuinely tiny. A standard DEXA scan delivers a fraction of the radiation you’d receive from a cross-country flight or a few days of normal background exposure. For context, the worldwide average effective dose from natural background radiation is about 2.4 millisieverts per year.⁶ A single DEXA scan delivers somewhere in the range of 1 to 10 microsieverts depending on the machine and the body sites scanned, which is a thousand-fold smaller than your annual background dose. Put another way, you get more radiation walking around outside for a day than from a DEXA scan.

Quantitative computed tomography (QCT), which some centers use as an alternative to DEXA, involves noticeably higher radiation because it uses a CT scanner. The dose is still far below a full diagnostic CT of the abdomen, but it’s enough of a difference that QCT isn’t the go-to choice for routine screening. The real appeal of QCT is that it can measure volumetric bone density (a true three-dimensional assessment) and can separate the spongy interior bone from the hard outer shell, which gives a different kind of clinical information than DEXA provides.

When Metal Implants and Other Artifacts Complicate Things

If you have a hip replacement, spinal hardware, or metal pins from a previous fracture repair, you might wonder whether a DEXA scan is still useful. Metal shows up brightly on X-ray-based imaging and can throw off the numbers in the immediate area of the implant. A replaced hip, for example, can’t give you a meaningful bone density reading on that side, so the technologist will scan the opposite hip instead.

Spinal implants are a bit more nuanced. Research using body phantoms has shown that spinal metal artifacts increase the apparent bone mass in the trunk area, but the effect on lean and fat mass estimates and on readings from the arms and legs stays within a clinically acceptable range.⁷ In practice, this means that if you have spinal hardware, the spine portion of your DEXA may not be reliable, but the hip and forearm measurements typically still are. Your technologist and radiologist will note any artifact on the report so your doctor knows which numbers to trust.

Degenerative changes in the spine, like bone spurs or disc calcification, can also inflate the spine reading and make bone density look better than it really is. This is more common in older adults and is one reason that the hip measurement is often considered more reliable than the spine in people over 65. Peripheral forearm DEXA sidesteps this problem entirely, since the forearm isn’t affected by the spinal calcification and degenerative changes that can corrupt spine readings in older women.²

Insurance Coverage and Repeat Scans

In the United States, Medicare covers bone density testing for beneficiaries who meet certain criteria, including women aged 65 and older and people on long-term steroid therapy or with other qualifying diagnoses. The coverage is governed by the Bone Mass Measurement Act, but the specifics of which diagnosis codes qualify and how often you can retest have led to some inconsistency. An analysis of Medicare claims found that about 5% of initial DEXA claims for women were denied, compared with roughly 9% for men. For repeat scans performed within about 23 months of the previous one, the denial rate jumped to around 19% regardless of sex, and varied dramatically by region, ranging from 2% to 43% depending on the local Medicare carrier.⁸

The takeaway for you is that if your doctor orders a repeat scan sooner than every two years, it’s worth checking with your insurance first to avoid a surprise bill. Most private insurers follow similar guidelines to Medicare, covering an initial screening at the recommended age and a repeat every 24 months for people with osteoporosis or risk factors. If you’re paying out of pocket, a DEXA scan typically runs somewhere between $100 and $300 depending on the facility and location.

Opportunistic Screening From CT Scans You’re Already Getting

An emerging approach to bone density testing requires zero extra time and no separate appointment. If you’re already getting a CT scan of your abdomen or pelvis for another reason, the images from that scan contain enough information to estimate your bone density. This is sometimes called opportunistic screening, and it works because the CT images already capture the lumbar vertebrae, which are a standard site for bone density assessment.⁹

Newer software using deep learning algorithms can now automate these measurements from routine CT scans with high accuracy. One validation study found that automated bone density measurements from CT images correlated very strongly with conventional manual QCT measurements, and the sensitivity and specificity for detecting osteoporosis were roughly 68% and 81%, respectively.¹⁰ Those numbers aren’t quite as sharp as a dedicated DEXA, but for people who are already in the scanner for something else, it’s essentially free bone density information that would otherwise go unnoticed.

This approach is especially promising for picking up osteoporosis in people who wouldn’t otherwise be screened, such as men or younger adults who happen to get a CT scan after an accident or for cancer surveillance. Hospitals that have adopted the technology can flag at-risk patients automatically, leading to earlier treatment without adding any imaging, radiation, or time to the patient’s visit. It’s not a replacement for DEXA when a dedicated bone density assessment is needed, but it’s a valuable safety net for catching bone loss that might otherwise slip through the cracks.