Most women should have their first DEXA scan at 65. At Longevity Benchmark, we've found that readers are more likely to get the timing of follow-up scans wrong than the timing of the first one.
DEXA stands for dual-energy X-ray absorptiometry. It measures bone mineral density at the hip and spine. But people use the same machine to answer two very different questions, and the right schedule depends on which one you're asking. If you're screening for bone loss, scans are typically spaced years apart. If you're tracking body composition for training, they may be done every few months.
The Verdict
When to Get a DEXA Scan for Bone Density Screening
The USPSTF recommends bone density screening for every woman at 65, and for postmenopausal women under 65 whose fracture risk is raised on a clinical risk assessment. Both carry a B recommendation, meaning the Task Force judged the net benefit moderate and told clinicians to offer the service. The final statement was published in JAMA on 14 January 2025.
| Group | What the guideline says | Grade or source |
|---|---|---|
| Women 65 and older | Screen for osteoporosis to prevent fractures | USPSTF, B recommendation |
| Postmenopausal women under 65 at raised risk | Screen when a clinical risk assessment estimates increased fracture risk | USPSTF, B recommendation |
| Men, any age | Evidence is insufficient to weigh the benefits against the harms | USPSTF, I statement |
| Men 70 and older | Measure bone mineral density | International Society for Clinical Densitometry (ISCD) and Bone Health and Osteoporosis Foundation (BHOF) |
| Men 50 to 69 with risk factors | Measure bone mineral density | BHOF |
| Women 50 to 64 with risk factors | Measure bone mineral density | BHOF |
| Anyone who broke a bone after 50 | Measure bone mineral density | BHOF and ISCD |
The men's row gets misquoted most often. An I statement means the evidence was too thin to weigh benefits against harms. So the USPSTF neither recommends screening men nor advises against it, and it has asked for research to settle the start age and the interval.
Two other bodies do publish an age. The ISCD and the Bone Health and Osteoporosis Foundation both put routine testing for men at 70, and at 50 to 69 with risk factors.
For women under 65, screening depends on a formal risk score rather than a birthday. Tools named in the USPSTF review include FRAX, the Osteoporosis Self-assessment Tool (OST) and the Simple Calculated Osteoporosis Risk Estimation (SCORE). That score decides whether a woman of 58 is in scope at all.
What Puts Someone Under 65 in Scope
A secondary cause of bone loss overrides the age threshold entirely. The ISCD sorts these into three groups: a fragility fracture in adulthood, a disease or condition associated with low bone mass, and a medication associated with bone loss. These are the ones that come up most often.
- Long-term glucocorticoid treatment. Prednisone and its relatives thin bone within months of starting, which is why steroid use is one of the conditions Medicare accepts for a covered scan.
- A fragility fracture after 50. A wrist, hip or spine broken in a fall from standing height is already evidence that the bone was weak, so the scan quantifies the problem rather than looking for it.
- Androgen deprivation therapy or an aromatase inhibitor. The ISCD names both as drugs that change bone density fast enough to warrant a shorter testing interval, which puts a prostate or breast cancer patient in scope at any age.
- Coeliac disease and other malabsorption. Poor absorption of calcium and vitamin D starves bone of its raw material, and timing that correction is covered in our guide to the best time to take vitamin D.
- A history of anorexia nervosa or another eating disorder. Low body weight and interrupted periods both appear in the risk-factor lists, and the bone lost in those years is not fully recovered later.
- Hypogonadism and rheumatoid arthritis. Both sit in the ISCD category of conditions associated with low bone mass, so either one moves the scan forward regardless of birthday.
- Early menopause or surgical removal of the ovaries. A shorter lifetime of estrogen exposure means bone loss starts sooner, and our page on the 3 stages of menopause explains where that acceleration falls.
Women stopping menopausal hormone therapy are singled out by the ISCD for consideration under those same indications. Our guide on when to start HRT covers what the bone argument does and does not support.
How Often to Get a DEXA Scan After the First One
Medicare covers a bone mass measurement once every 24 months for beneficiaries who meet a qualifying condition, and more often when it is medically necessary. The five qualifying conditions it lists are estrogen deficiency with osteoporosis risk, X-rays suggesting osteoporosis, osteopenia or vertebral fracture, current or planned steroid treatment, primary hyperparathyroidism, and monitoring of osteoporosis drug therapy.
A benefit cycle is not a clinical interval. The USPSTF reports that cohort studies of screening intervals found repeating bone mineral density testing at 4 to 8 years did not add accuracy in predicting fractures. The ISCD declines to publish a fixed number at all, stating instead that repeat intervals must be individualised by age, baseline density, treatment and the clinical factors driving bone loss.
Shorter gaps are for people whose bone is moving fast. The ISCD lists glucocorticoids, aromatase inhibitors, androgen deprivation therapy and osteoanabolic drugs as reasons to scan sooner.
The Bone Health and Osteoporosis Foundation suggests a repeat 1 to 2 years after starting or changing an osteoporosis medication. Everyone else is waiting for a change the machine can see.
The Arithmetic Behind the Long Interval
A repeat scan can only report a change larger than the machine's own error. The ISCD calls that threshold the least significant change, and it is calculated by multiplying the scanner's measured precision error by 2.77, which gives 95% confidence that a difference is real.
The Society caps the worst acceptable precision a technologist may have at 1.9% for the lumbar spine, 1.8% for the total hip and 2.5% for the femoral neck. Those work out to least significant change values of 5.3%, 5.0% and 6.9%.
Put those next to how fast bone moves. Bone loss speeds up for about three years around the final menstrual period. Across that window, the Study of Women's Health Across the Nation (SWAN) recorded average annual losses in white women of 2.5% at the lumbar spine and 1.8% at the femoral neck.
Those figures are set out in Bone Health during the Menopause Transition and Beyond. That is the fastest phase most women will ever have.
| Site | Worst acceptable precision error | Least significant change | Fastest SWAN loss rate | Time to clear the error |
|---|---|---|---|---|
| Lumbar spine | 1.9% | 5.3% | 2.5% a year | About 2 years |
| Femoral neck | 2.5% | 6.9% | 1.8% a year | Nearly 4 years |
| Total hip | 1.8% | 5.0% | Not reported separately by SWAN | Longer than 12 months on any published rate |
Divide the least significant change by the yearly loss rate and you get the wait. At the lumbar spine, 5.3% of change at 2.5% a year takes about two years to appear, and at the femoral neck, 6.9% at 1.8% a year takes nearly four. Outside the menopause transition, loss is slower and the wait is longer still.
How Much Radiation a DEXA Scan Uses
A DEXA scan is an X-ray and the dose is very small. RadiologyInfo.org is run by the Radiological Society of North America and the American College of Radiology. It puts the effective dose at less than one tenth of a standard chest X-ray, and at less than a day of natural background exposure.
The Bone Health and Osteoporosis Foundation makes the same comparison against a cross-country flight. The USPSTF found the evidence on screening harms limited overall, and the screening trial it cites on psychological effects reported no difference in anxiety between screened and unscreened women.
So the reason not to over-scan is not the radiation. It is that the result will not have changed.
Two cautions still apply. Tell the technologist if you are pregnant or think you might be, since pregnancy is the one situation where an avoidable X-ray gets postponed. Recent barium or injected contrast can also spoil the images, so scans are usually deferred a couple of weeks afterwards.
Scanning for Body Composition Runs on a Different Clock
A DEXA scan booked to measure body composition should be repeated every 3 to 6 months, not every few years. Fat mass and lean mass respond to a training block or a sustained calorie deficit within weeks, so that spacing catches a change worth acting on. Bone remodels over years, which is the whole reason the two uses of the same machine cannot share an interval.
In the guides we publish here, one mix-up turns up more than any other. A reader applies the two-year bone rhythm to a body composition scan, then wonders why a training programme appeared to do nothing. The reverse error costs money instead of information, since quarterly bone scans buy nothing but noise.
Our page on DEXA body composition covers what those numbers support, and grip strength by age is a cheaper way to track whether the lean mass you are building does any work.
Who Should Not Get a DEXA Scan Yet
A premenopausal woman with no fragility fracture, no steroid use and no secondary cause gains almost nothing from a bone density scan. Her result comes back as a Z-score against her own age group, so a low reading prompts a hunt for a cause rather than a treatment decision. Our page on the DEXA scan T-score explains why the two scores answer different questions.
The same applies to a healthy man in his fifties with none of the risk factors on the list, and to anyone whose scan came back normal in the past two years. Both should run a fracture risk assessment with their doctor instead. Keep weight-bearing and resistance training in the week, and book the scan when a risk factor or an age threshold arrives.
New evidence on intervals would change our answer. The USPSTF has asked for decision analysis work on the optimal start age, stop age and screening interval in women. A trial resolving the I statement for men would move that row from silence to a number.
Until then, if you are deciding when to get a DEXA scan, ask your doctor to run FRAX or an equivalent risk assessment first and book the scan the result points to.
Frequently Asked Questions
How often should you get a DEXA scan?
After a reassuring first scan, several years. The US Preventive Services Task Force reports that cohort studies of screening intervals found repeating bone mineral density testing at 4 to 8 years did not add accuracy in predicting fractures. Glucocorticoids, androgen deprivation therapy and aromatase inhibitors all move bone fast enough to justify a shorter gap.
Is a DEXA scan every 2 years necessary?
No, and the 24-month figure is a billing cycle rather than a clinical interval. Medicare covers a bone mass measurement once every 24 months for beneficiaries who meet a qualifying condition, and more often when it is medically necessary. Being allowed a scan every two years does not mean one will tell you anything new.
At what age should you start getting DEXA scans?
65 for women, unless something moves you earlier. The USPSTF gives that a B recommendation, and the same grade to screening postmenopausal women under 65 whose fracture risk is raised on a formal clinical risk assessment. The Bone Health and Osteoporosis Foundation adds men at 70, men aged 50 to 69 with risk factors, and women aged 50 to 64 with risk factors.
Does Medicare pay for a DEXA scan every year?
Not routinely. The benefit runs once every 24 months, and Medicare pays for a repeat sooner only when the ordering clinician documents that it is medically necessary for one of the qualifying conditions. Monitoring someone on long-term glucocorticoid therapy is the example the Medicare Benefit Policy Manual gives. A yearly scan a patient asks for without that documentation is billed to the patient. You pay nothing for a covered test when the provider accepts assignment.
Is a DEXA scan safe?
Yes. DEXA stands for dual-energy X-ray absorptiometry, so it is an X-ray by definition, and the dose is among the smallest in diagnostic imaging. RadiologyInfo.org, run by the Radiological Society of North America and the American College of Radiology, puts the dose at less than one tenth of a standard chest X-ray. That is under a day of natural background exposure. Tell the technologist if you are pregnant or might be.
What are the indications for a DEXA scan besides age?
The International Society for Clinical Densitometry groups them into three: a fragility fracture in adulthood, a disease or condition associated with low bone mass, and a medication associated with bone loss. In practice that covers long-term glucocorticoids, androgen deprivation therapy, aromatase inhibitors, malabsorption, an eating disorder history, hypogonadism, rheumatoid arthritis and early menopause. None of these wait for 65.
Do DEXA scan guidelines for women differ from those for men?
They do, because the evidence base differs rather than because bone does. The USPSTF issued an I statement for men, meaning it could not weigh benefits against harms with the trials available. The ISCD and the Bone Health and Osteoporosis Foundation both name 70 as the routine testing age for men, and 50 to 69 with risk factors. A man on androgen deprivation therapy is in scope at any age.
How often should you get a DEXA scan for body composition?
Every 3 to 6 months, a much shorter cycle than the bone one. Fat mass and lean mass respond to a training block or a calorie deficit inside a few months, so that spacing catches a real change. Our guide to DEXA body composition results covers what the lean mass and visceral fat numbers support.