A DEXA (Dual-Energy X-ray Absorptiometry) bone scan is a powerful diagnostic tool used by healthcare professionals to assess bone mineral density (BMD) and diagnose conditions like osteoporosis, osteopenia, and other bone-related disorders. It’s a quick, painless, and highly accurate procedure, but its effectiveness depends heavily on proper preparation. Even small missteps in the days or hours leading up to the scan can compromise the results, leading to inaccurate diagnoses and inappropriate treatment plans.
If you’re scheduled for a DEXA scan, understanding what to avoid is just as important as knowing what to do. This comprehensive guide outlines the mistakes you should never make before undergoing a DEXA bone scan, helping you ensure the most reliable diagnosis possible.
Understanding the DEXA Bone Scan: Why Accuracy Matters
Before diving into what not to do, it’s essential to understand why the DEXA scan is a gold standard in bone health evaluation. The technology uses two low-dose X-ray beams of different energy levels to measure the amount of calcium and other minerals in your bones. Areas commonly scanned include the spine, hip, and forearm—all key areas vulnerable to fractures in individuals with bone loss.
The DEXA scan produces a T-score, which compares your bone density to that of a healthy young adult of the same sex. A T-score of -1.0 or above is considered normal; between -1.0 and -2.5 indicates osteopenia; and below -2.5 suggests osteoporosis.
Because treatment decisions are based on these scores, any interference with the scan’s results could lead to under-treatment or over-treatment. For example, falsely low readings could prompt unnecessary medication, while falsely high scores might overlook a real pathology.
Common Factors That Affect Bone Density Readings
Several external and internal variables can skew bone density measurements. These include:
- Recent intake of calcium supplements or contrast materials
- Wearing clothing with metal components
- Recent imaging procedures involving barium or contrast agents
- Improper positioning during the scan
- Recent fractures or orthopedic surgeries
Being aware of these influencing factors is the first step in avoiding errors.
1. Don’t Take Calcium Supplements 24 to 48 Hours Before the Scan
One of the most critical rules is to avoid taking calcium supplements for at least 24 to 48 hours before your DEXA scan. This includes calcium in any form—tablets, chewables, vitamins with high calcium content, or even antacids containing calcium carbonate (such as Tums).
Why Calcium Supplements Interfere
Calcium supplements can settle in your digestive tract and appear on the scan as dense mineral deposits. Since DEXA scans measure mineral density, undigested calcium in your stomach or intestines might be mistakenly interpreted as part of your bone structure. This artifact can inflate bone density readings, particularly in spinal scans, leading to an inaccurate assessment.
Real-World Consequences
An inflated T-score could result in:
- False reassurance that your bones are healthier than they are
- Delayed treatment for osteopenia or osteoporosis
- Increased risk of future fractures due to lack of intervention
Even small amounts matter—don’t assume that a single tablet won’t affect your results. Consistency and caution are key.
Alternative Supplement Management
If you’re on a calcium supplement regimen for a medical condition:
- Consult your doctor several days in advance about pausing your supplements.
- Consider switching to a non-calcium antacid if you need stomach relief during the hold period.
- Resume your normal regimen only after the scan and with your doctor’s approval.
2. Never Wear Jewelry or Metal During the Scan
While this may seem obvious, many patients overlook the impact that everyday accessories can have on imaging results.
What Qualifies as Metal?
Metal objects that should be removed before the scan include:
- Necklaces, rings, bracelets, and earrings
- Belt buckles with metal components
- Clothing with zippers, metal buttons, underwires (e.g., bras), or decorative embellishments
- Watches and electronic fitness trackers
How Metal Affects the Results
Metal produces high-density signals on the DEXA scan. These signals can:
- Obscure the bone being measured
- Create false “hot spots” that mimic dense bone tissue
- Require the technologist to repeat the scan, leading to delays and potential increased radiation exposure
Even small pieces of metal near the spine or hip can distort bone density readings. Most clinics will ask patients to change into a hospital gown to eliminate this risk.
Tips for Preparing Your Clothing
To avoid last-minute issues:
- Wear loose-fitting clothes without metal fasteners
- Leave jewelry at home if possible
- Carry a small pouch for removing and storing items before the scan
3. Avoid Recent Barium Studies or Contrast Imaging
If you’ve recently undergone imaging tests such as a CT scan with contrast, an MRI with gadolinium, or a barium swallow/enema, it’s crucial to inform your healthcare provider before scheduling your DEXA scan.
How Contrast Agents Cause Interference
Barium and iodine-based contrast materials are radiopaque, meaning they appear bright and dense on X-ray imaging. These substances can linger in your gastrointestinal tract for several days after a procedure. When present during a DEXA scan—especially one focusing on the spine—they may be misread as increased bone density.
Recommended Time Gap
To ensure a clear scan:
- Wait at least 7–14 days after a barium study before scheduling your DEXA scan.
- Inform your radiologist if you’ve had any contrast-based imaging within the past two weeks.
Scheduling your bone density scan before any contrast procedures is ideal. Always discuss your diagnostic history with your referring physician.
4. Don’t Ignore Medication Timing and Interactions
Some medications—even those not containing calcium—can affect scanning accuracy or bone health interpretation.
Supplements and Multivitamins
Many multivitamins contain calcium, vitamin D, or other minerals. Carefully check the labels. If they contain calcium, avoid taking them before the scan. For example:
| Supplement | Caution Level |
|---|---|
| Multivitamin with calcium | High – Avoid 48 hours before scan |
| Vitamin D without calcium | Low – Usually safe |
| Iron supplements | Moderate – Metal content may interfere slightly |
Discuss all supplements with your physician, especially if you’re unsure.
Prescription Medications
Certain medications for osteoporosis (like bisphosphonates) or thyroid disorders don’t interfere directly with the scan, but timing your dosages (e.g., taking them on the day of the scan) might affect comfort or digestion. Always:
- Inform your doctor about all prescription medications.
- Follow their guidance on whether to take your medicine on scan day.
5. Never Schedule a DEXA Scan Soon After a Fracture or Surgery
If you’ve recently experienced a bone fracture, spinal injury, or orthopedic surgery, it’s wise to delay your DEXA scan.
Why Healing Bone Skews Results
During the healing process, the body increases bone remodeling at the injury site. This leads to:
- Localized increases in mineral density
- Inflammation and fluid buildup that may interfere with imaging
- Altered biomechanics, making proper positioning difficult
The scan results from an affected area may falsely appear healthier, masking underlying bone loss in other regions.
Recommended Waiting Period
As a general rule:
- Wait at least 3–6 months after a fracture before scanning the affected area.
- For spinal fractures, alternative sites (like the forearm or non-fractured hip) may be used.
Your radiologist will determine the best approach based on your individual medical history.
6. Do Not Eat or Drink Calcium-Rich Foods Before the Scan
It’s not just supplements—your diet matters, too. Avoid consuming large amounts of calcium-rich foods within 24 hours of your appointment.
Common Calcium-Rich Foods to Avoid
These items can introduce calcium into your digestive system and potentially interfere:
- Dairy products (milk, cheese, yogurt)
- Fortified orange juice or plant-based milks
- Leafy greens like kale or spinach (in large quantities)
- Calcium-fortified cereals or snack bars
While ingested dietary calcium is less concentrated than supplements, consuming a large calcium-rich meal shortly before scanning can still contribute to imaging artifacts, especially in spinal assessments.
Better Pre-Scan Meal Choices
Stick to meals that are:
- Low in calcium
- Light and easily digestible
- Free from dairy or fortified ingredients
For example, a plain rice dish with steamed vegetables (excluding high-calcium greens) and grilled chicken is a safer choice.
7. Avoid Excessive Physical Activity Right Before the Scan
While regular exercise supports bone health, intense physical activity within 24 hours of your DEXA scan should be avoided.
How Exercise Impacts Imaging
Strenuous workouts—especially weight training or high-impact activities—can cause:
- Micro-inflammation or swelling in bones and muscles
- Fluid retention that may affect body composition readings (if a body composition scan is included)
- Temporary changes in blood flow and mineral distribution
While this is a lesser-known factor, some studies suggest that acute muscle fatigue can influence soft-tissue measurements, which in turn may affect bone density interpretation in dual-component scans.
Recommended Activity Level
In the day before your scan:
- Avoid heavy lifting or intense training sessions.
- Light walking or stretching is fine.
- If you’re undergoing a full-body DEXA for body composition, hydration and activity become even more critical.
8. Never Keep Your Doctor in the Dark About Medical History
Transparency with your healthcare provider is vital for accurate diagnosis and safe testing.
What to Disclose
Be sure to inform your doctor about:
- Past fractures, especially spinal or hip injuries
- Recent surgeries or implants (e.g., hip replacements, spinal rods)
- History of gastrointestinal surgeries (e.g., gastric bypass) that affect nutrient absorption
- Pregnancy or potential pregnancy (DEXA uses low-dose radiation)
- Current medications that affect bone metabolism (e.g., steroids, anticonvulsants)
Why This Matters
Radiologists use this information to:
- Choose the best scanning sites
- Interpret results in the context of your individual health
- Flag results that might be affected by artifacts (e.g., metal implants)
For example, if you have a hip replacement, your hip cannot be scanned, but the spine or forearm can still provide useful data.
9. Skip Coffee or Caffeinated Beverages Immediately Before the Scan
While not as impactful as calcium supplements, excessive caffeine can affect your positioning and comfort during the scan.
The Hidden Effects of Caffeine
Caffeine is a stimulant. Consuming large amounts right before the scan may:
- Increase anxiety or restlessness
- Make it harder to remain still during the 10–20 minute procedure
- Affect hydration levels, potentially skewing body composition results in full-body DEXA scans
Better Beverage Choices
Stick to water or decaffeinated herbal teas the morning of your appointment. Avoid energy drinks, coffee, and caffeinated sodas.
10. Don’t Rush the Procedure or Ignore Technologist Instructions
Your cooperation during the scan is just as important as your preparation.
Why Proper Positioning Matters
DEXA results rely on precise alignment. If you’re:
- Moving during the scan
- Not lying flat or straight
- Incorrectly positioning your limbs
…your results may vary significantly. For example, subtle rotation of the hip can reduce femoral neck density readings by up to 5–10%, which could shift a diagnosis from osteopenia to normal or vice versa.
Tips for a Smooth Scan
- Arrive early to avoid stress.
- Follow the technologist’s positioning guidance carefully.
- Breathe normally and remain still during imaging.
Remember: even the most advanced technology depends on human cooperation for accuracy.
Final Checklist: What to Do the Day Before and Day of Your DEXA Scan
To summarize, here’s what you should do to prepare properly:
- Stop calcium supplements 24–48 hours before the scan.
- Avoid calcium-rich meals and drinks the day before.
- Wear loose, metal-free clothing.
- Remove all jewelry and metal objects before entering the scan room.
- Ensure at least a 7–14 day gap after barium or contrast imaging.
- Inform your doctor of fractures, surgeries, or implants.
- Avoid intense workouts 24 hours prior.
- Limit caffeine on the morning of the scan.
- Follow all instructions from your healthcare team precisely.
Conclusion: Preparation Is Prevention
Your DEXA bone scan is more than just a routine test—it’s a window into your long-term skeletal health. Ensuring accurate results isn’t about perfection; it’s about mindfulness. By avoiding the mistakes outlined above, you take active control of your diagnosis and treatment plan.
Remember: when it comes to DEXA scans, what you do before the test is just as critical as the test itself. Avoid calcium ingestion, metal wear, recent contrast studies, and miscommunication with your healthcare team. With proper preparation, you can trust your results and move forward with confidence in your bone health journey.
Schedule your scan wisely, prepare diligently, and always consult your doctor when in doubt. Your bones depend on it.
What Should You Never Wear During a DEXA Bone Scan?
You should never wear clothing with metal zippers, buttons, belts, or underwire bras during a DEXA bone scan. Metal components can interfere with the low-dose X-ray imaging used in the scan, creating artifacts on the images that may obscure bone density measurements or lead to inaccurate results. Even jewelry, watches, or hairpins containing metal should be removed before the procedure to ensure a clear and accurate assessment of bone health.
Instead, it’s best to wear loose, comfortable clothing free of any metallic elements. Many imaging centers provide a hospital gown to change into, eliminating the risk of interference entirely. Wearing appropriate attire not only ensures accuracy but also helps streamline the scanning process, reducing the need for re-scanning due to image distortions, ultimately saving time and reducing potential anxiety for patients.
Why Should You Avoid Calcium Supplements Before the Scan?
Calcium supplements should be avoided for at least 24 to 48 hours before a DEXA bone scan because they can appear as dense material on the X-ray images. If you’ve recently taken a supplement, the calcium may accumulate in your digestive tract, particularly in the abdomen, which could be mistaken for areas of increased bone density or interfere with spine imaging results. This interference can lead to misinterpretation of the scan and potentially inaccurate diagnosis or monitoring of osteoporosis.
To ensure the most accurate results, discontinue calcium supplements, including multivitamins that contain high levels of calcium, before your appointment. Always check with your doctor or the imaging center for their specific guidelines, as recommendations may vary. This simple precaution helps ensure that the measured bone mineral density reflects your actual skeletal health, not residual supplement content.
Is It Harmful to Schedule Other Imaging Tests Right Before a DEXA Scan?
Yes, scheduling other imaging tests that use contrast agents—such as CT scans, MRI with contrast, or nuclear medicine studies—shortly before a DEXA scan can negatively impact the results. Contrast materials, especially those containing barium or iodine, remain in the body for some time and can interfere with the X-ray absorption measurements used in DEXA technology. If these substances are present, they may falsely elevate bone density readings, particularly in the spine or hip regions being scanned.
To avoid this interference, it’s recommended to wait at least 7 to 10 days after a contrast-enhanced imaging test before undergoing a DEXA scan. Always inform your healthcare provider if you’ve had recent imaging procedures so they can determine the appropriate timing. Proper scheduling helps ensure the scan provides reliable data essential for evaluating bone strength and fracture risk.
Should You Exercise Rigorously the Day Before a DEXA Scan?
Rigorous exercise the day before a DEXA bone scan is not recommended because it can temporarily influence fluid distribution and soft tissue composition in the body. Intense physical activity may lead to slight swelling or changes in muscle hydration, which could affect the scanner’s ability to accurately differentiate between bone and soft tissue. While the impact may be minor, consistency in pre-scan conditions helps ensure reliable and comparable results over time.
For best results, stick to your normal daily routine and avoid heavy workouts, especially those targeting the areas being scanned, such as the spine or hips. Light walking or gentle stretching is acceptable. Maintaining a stable physiological state before the scan enhances accuracy, particularly if you are being monitored annually to track changes in bone density.
Can You Eat Normally Before a DEXA Bone Scan?
While you can generally eat normally before a DEXA scan, it’s important to avoid eating a heavy meal immediately before the appointment. A full stomach can shift internal organs and potentially affect how the body lies during imaging, particularly when scanning the spine. Additionally, consuming foods rich in calcium, such as dairy products, close to the scan may increase calcium residue in the gastrointestinal tract, which could interfere with image clarity.
Most guidelines suggest fasting for a few hours before the scan or eating a light meal if necessary. The goal is to minimize variables that could distort the scan’s precision. Always follow the specific instructions given by your imaging center, but in general, maintaining a balanced approach to eating—neither fasting too long nor overeating—will support the most accurate assessment of your bone health.
Why Should You Avoid Wearing Lotion or Powder Before the Scan?
Wearing lotions, creams, or body powders before a DEXA scan is discouraged because some products contain minerals like calcium, magnesium, or metallic compounds that can settle on the skin and appear in the scan images. These substances may mimic bone density patterns or create signal interference, leading to misleading results, especially in areas where the skin contacts the scanning table. Even small amounts of residue can compromise the clarity and diagnostic value of the scan.
To prevent this, it’s best to avoid applying any topical products to your skin on the morning of the scan, particularly on the back, hips, and arms. Showering with plain soap and water beforehand is ideal. This precaution is simple but essential for obtaining accurate and consistent measurements, especially when monitoring changes in bone density over time.
What Happens If You Don’t Inform Your Technician About Recent Fractures or Surgeries?
Failing to inform your DEXA technician about recent fractures, spinal surgeries, or joint replacements can lead to inaccurate bone density readings. Metal implants, surgical hardware, or healing bones alter the local density and structure of the skeletal site, which the scanner may misinterpret as abnormal bone density patterns. For example, a hip replacement can make the area appear artificially dense, interfering with meaningful results from that region.
Always disclose your complete medical history, especially any orthopedic procedures or injuries, so the technician and radiologist can choose appropriate scan sites and interpret the data correctly. In some cases, alternative areas may be scanned to avoid interference. Full transparency ensures that the results are both accurate and clinically useful for managing your long-term bone health.