For most people, a bone density test doesn’t mean getting undressed. You can often stay in your own clothes.1Radiologyinfo.org. Bone Densitometry Whether you change comes down to one thing: metal on your clothing near the hip and lower back.
When You Might Need to Change Into a Gown
A bone density test, called a DEXA or DXA scan, uses low-dose x-rays to measure how thick and strong your bones are, usually at the hip and spine.2National Center for Environmental Health. Facts About Bone Density Because the scanner looks mainly at the hip and lower spine, anything metal sitting over your waist, hips or lower back can end up in the picture. That’s when you may need to remove some clothing or change into a gown for the exam.3Radiologyinfo.org. Bone Densitometry You may also be asked to take off jewelry, eyeglasses and any clothing that could interfere with the images.4National Center for Environmental Health. Facts About Bone Density (DEXA Scan)
Jeans are the most common culprit, since they usually have a metal button, zipper and rivets right over the hip area. Belts with buckles and metal-trimmed waistbands sit directly over the lower spine. Sequins, metal studs or snaps near the waist can also cause trouble. Underwire bras rarely matter for hip and spine views, though some centers still ask you to remove them, especially if a forearm is scanned.
Changing is simple. You’re usually shown to a private changing room or cubicle, and you typically keep your underwear on and swap only the item with metal. If your own clothes won’t work, the center offers a gown or loose scrub-style trousers.
The technologist usually decides when you arrive, glancing at your waistband, pockets and fasteners. Leggings, soft trousers and a plain top often pass without any change.
If undressing worries you, you can ask ahead what the center’s gown policy is. You can also ask for a chaperone, or for a staff member of a particular sex, if that would help.
What to Wear So You Can Stay Dressed
Wear loose, comfortable clothes without zippers, buttons or belts, and leave jewelry at home.5Mayo Clinic. Bone density test (DXA/DEXA scan) Take keys, coins and wallets out of your pockets before the scan.6Radiologyinfo.org. Bone Densitometry Removable dental appliances may also need to come out.7Radiologyinfo.org. Bone Densitometry
Elastic-waist trousers, leggings or track pants work well, as long as the drawstring has no metal tips. Pair them with a plain T-shirt or sweatshirt that has no metal zips. Slip-on shoes make the visit easier, though your feet aren’t scanned.
People often forget the small things: a phone or keys left in a pocket, a hair clip, or a piercing near the navel. Shapewear can have metal hooks at the waist. Plastic buttons are usually fine; it’s metal that matters.
The night before, run your fingers along the waistband and seams of the clothes you plan to wear. Anything hard or cold to the touch may be metal, so pick something else if you’re unsure. If your only comfortable trousers have a zip, wear them anyway and change at the center, or tuck a spare elastic-waist pair into your bag.
Why Metal Matters for the Scan
The scan sends a high-energy and a low-energy x-ray beam through your body.8National Center for Environmental Health. Facts About Bone Density Comparing the two lets the machine separate bone from soft tissue.9MTMI. DXA Uses: Bone Density & Body Composition Metal can interfere with the results,10National Center for Environmental Health. Facts About Bone Density (DEXA Scan) so a buckle over the spine could make bone look denser than it really is, which could hide real thinning.
The scanner measures how much x-ray is absorbed along the path through you, and it can’t tell on its own whether the absorbing material is bone or a zipper. Metal absorbs x-rays far more strongly than bone does, so even a small piece can look like a patch of dense bone. Technologists review the image and may spot a stray object, but one that goes unnoticed can still slip into the measurement. Removing it beforehand is more reliable. If staff catch the problem, they may have to redo the scan, which adds time.
Metal inside the body is a different matter. Tell staff about hip replacements, spinal rods or other implants. Since hardware can’t be taken off, the technologist works around it, perhaps scanning the other hip or the forearm instead. The report may note which sites were left out, so your doctor knows the score comes from a different bone.
Other Things to Avoid Before Your Scan
Many scan centers ask you not to take calcium supplements before the test, because a calcium tablet can change a lower-spine reading within 30 minutes of swallowing it.11PubMed. Calcium supplement ingestion may alter lumbar spine bone mineral density measurement Tablets may not have dissolved fully and can show up in the images near the spine. Hold your supplement until after the scan that day. If you take calcium daily, you’re only delaying it, not skipping it for good. Check whether your antacid or multivitamin contains calcium, since those count too.
A CT scan with contrast dye is different: it can distort results if done within the week before.12PubMed. Effect of diagnostic radioisotopes and radiographic contrast media on measurements of lumbar spine bone mineral density and body composition by dual-energy x-ray absorptiometry If you’ve had one, tell the center. They may reschedule for at least 7 days later. You can usually eat and drink as normal, and keep taking prescription medicines unless you’re told otherwise.
When booking, mention a possible pregnancy, because the test uses x-rays. Also mention a recent barium test or nuclear medicine scan. Tables have weight limits, so say so if you’re heavy.
What Happens During the Scan
At the start, the technologist asks you to confirm your name and may ask your height and weight, which go into the machine along with your age and sex. They help you position yourself and adjust the supports so you’re comfortable and aligned.
You lie on your back on a flat, open padded table.13nhs.uk. Bone density scan (DEXA scan) – How it is performed For the spine, your legs rest on a padded box to flatten your lower back.14Radiologyinfo.org. Bone Densitometry For the hip, your foot is placed in a brace that turns the hip slightly inward.15Radiologyinfo.org. Bone Densitometry A detector arm then moves slowly above you while the x-ray source sits below the table.16Radiologyinfo.org. Bone Densitometry You need to keep still so the images aren’t blurred,17nhs.uk. Bone density scan (DEXA scan) – How it is performed and the scan usually takes 10 to 20 minutes.18nhs.uk. Bone density scan (DEXA scan) – How it is performed
There are no needles, and nothing touches you except the supports. The machine is open rather than a tunnel. You may hear a soft whirring as the arm moves, and you can usually go straight back to normal activities afterwards.
Staying still doesn’t mean holding your breath. Breathe normally and just avoid moving your body while the arm passes over you. If you need to cough, sneeze or shift, tell the technologist, who can pause the scan or repeat that part. Blurring from movement is a common reason a view has to be repeated.
Some pharmacies offer a quick heel ultrasound or finger check with no undressing. These miss many cases: one heel test found only 7 of 22 women who had osteoporosis on the main scan.19PubMed. Comparison of heel ultrasound and finger DXA to central DXA in the detection of osteoporosis. Implications for patient management A normal heel result doesn’t rule out osteoporosis or replace the hip and spine scan your doctor orders.
Is the Radiation Safe
Everyone takes in natural radiation daily, about 10 microsieverts a day.20International Atomic Energy Agency. Radiation protection of patients during DXA A modern hip and spine scan gives a dose about equal to or below one day of that background.21International Atomic Energy Agency. Radiation protection of patients during DXA That’s usually less than a chest x-ray, which is 20 to 50 microsieverts.22International Atomic Energy Agency. Radiation protection of patients during DXA The machine keeps the dose low by aiming a narrow beam only at the areas being measured. The dose is small enough that staff can stay nearby rather than leaving the room.
Understanding Your Results
Your report gives a T-score, which compares your bones with those of a healthy young adult. The ranges are:
- Normal, +1 to -1: bone density in the normal range for a young adult.23Royal Osteoporosis Society. Osteoporosis: Bone density scan (DEXA)
- Low bone density (osteopenia), -1 to -2.5: slightly below normal, and expected in older adults.24Royal Osteoporosis Society. Osteoporosis: Bone density scan (DEXA)
- Osteoporosis, -2.5 and below: much lower than a young adult’s.25Royal Osteoporosis Society. Osteoporosis: Bone density scan (DEXA)
Your report may also show a Z-score, which compares your bones with people your own age and sex.26PubMed. Use of dual-energy X-ray absorptiometry (DXA) for diagnosis and fracture risk assessment; WHO-criteria, T- and Z-score, and reference databases A much lower than expected result can prompt your doctor to look for another cause of bone loss.
Arthritis bone spurs in the spine can raise readings by up to 14%, making bones look stronger.27PubMed. Impact of spinal degenerative changes on the evaluation of bone mineral density with dual energy X-ray absorptiometry (DXA) So doctors often look at the hip score too if your spine has arthritis.
The numbers aren’t a diagnosis on their own. Your doctor also considers your age, past fractures, family history and medicines. Two people with the same score can have different chances of breaking a bone. Low bone density is common with age and doesn’t mean your bones are failing or that you will break one. Many people in that range are advised to focus on activity, diet and monitoring, with medicine considered only if overall risk is high.
Useful questions for your doctor: which site gave your lowest score, since treatment decisions often use it; whether arthritis or an old fracture could be affecting the spine number; and what your overall fracture risk is, not just the score.
Exercise, enough calcium and vitamin D, not smoking and treatment where needed can all affect bone over time. Keep a copy of your report for comparison with your next scan.
Who Needs the Test and How Often
Screening is recommended for all women 65 and older.28JAMA. Osteoporosis to Prevent Fractures: Screening It’s also recommended for younger postmenopausal women at higher risk of fractures.29JAMA. Osteoporosis to Prevent Fractures: Screening For men, there isn’t enough evidence to say whether routine screening helps.30JAMA. Osteoporosis to Prevent Fractures: Screening Men with risk factors, such as a past fragility fracture or long-term steroid use, may still be tested after talking with their doctor.
A younger postmenopausal woman counts as higher risk if she has had a previous fracture, has a parent who broke a hip, has low body weight, or smokes. Long-term use of steroid tablets such as prednisone is another common reason for earlier testing.
Repeat scans are usually every 2 years if high risk, every 3 to 5 years if moderate, and 10 to 15 years if low.31MedlinePlus. Bone Density Scan: MedlinePlus Medical Test Bone changes slowly, so a scan a year later often shows a difference smaller than the machine’s own measurement error. Your doctor chooses the interval from your score and risk, so ask what yours is rather than assuming it matches a friend’s. In the US, Medicare refused about 19% of claims for scans repeated within 23 months,32PubMed Central. Regional Variation in the Denial of Reimbursement for Bone Mineral Density Testing Among U.S. Medicare Beneficiaries so check coverage before booking an early repeat.
Machines differ slightly, so repeating at the same center makes comparisons fairer. Wear similar metal-free clothes each time, and bring the date of your last scan when booking.