What a DEXA Scan Is and Why Doctors Order Them
A DEXA scan, which stands for Dual-Energy X-ray Absorptiometry, is a medical imaging test that measures bone mineral density. Unlike a standard X-ray that shows whether bones are broken, a DEXA scan detects how dense your bones are and whether they may be at risk for fractures. The test uses very low levels of radiation—about one-tenth of what you receive during a chest X-ray—to take detailed pictures of your skeleton.
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Doctors order DEXA scans for several important reasons. The primary reason is to screen for osteoporosis, a condition where bones become brittle and more likely to break from minor falls or accidents. According to the National Osteoporosis Foundation, about one in three women and one in five men over age 50 will experience an osteoporosis-related fracture in their lifetime. A DEXA scan can detect bone loss years before a fracture occurs, allowing doctors to recommend treatment or lifestyle changes to prevent serious injury.
DEXA scans may also be ordered if you have risk factors for bone loss, including being over age 50, having a family history of osteoporosis, taking certain medications like corticosteroids, or having conditions that affect bone health such as rheumatoid arthritis or hyperthyroidism. Some people receive DEXA scans to monitor whether treatments for bone loss are working over time.
The test typically takes 10 to 30 minutes and is painless. You lie on a padded table while a scanning arm moves slowly over your body, most commonly measuring bone density in your hip, spine, and sometimes your forearm. The machine produces a detailed report showing your bone mineral density compared to healthy young adults, which helps doctors assess your fracture risk.
Practical takeaway: Understanding that a DEXA scan detects bone density rather than breaks helps you know what to expect and why your doctor is recommending the test.
Pre-Scan Preparation: What to Do Before Your Appointment
Preparing for a DEXA scan involves several straightforward steps that help ensure you get accurate results. Most preparation involves what you should avoid rather than complicated procedures. About 24 hours before your scan, you should stop taking any calcium supplements. Calcium tablets can interfere with the imaging and make bones appear denser than they actually are. If you take a multivitamin containing calcium, skip it on the day of your scan. This does not mean stopping calcium-rich foods like milk, yogurt, or leafy greens—only supplemental tablets need to be held.
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On the day of your appointment, wear comfortable, loose clothing without metal zippers, buttons, or fasteners. Metal can interfere with the scan results, so clothing made of cotton or other natural fibers works best. Avoid wearing jewelry, including watches, rings, and necklaces. If you have had other imaging tests recently, such as CT scans or nuclear medicine studies, let your healthcare provider know, as some contrast dyes used in those tests may affect DEXA results.
Eating and drinking normally before a DEXA scan is fine—you do not need to fast. You can take your regular medications unless your doctor has specifically told you otherwise. However, do not take calcium supplements on the day of the scan, as mentioned above. If you are pregnant or think you might be, inform your healthcare provider immediately, as DEXA scans use radiation and should not be performed during pregnancy.
Arrive 10 to 15 minutes early to allow time for check-in and paperwork. Bring your insurance card and a photo ID. When you arrive, the technician will ask about your medical history, any previous bone density tests, and your current medications. Being honest and detailed during this conversation helps the technician perform the most accurate scan. Write down any questions you have beforehand so you remember to ask them.
Practical takeaway: Stop calcium supplements 24 hours before your scan, wear metal-free clothing, and arrive early with your insurance information to ensure a smooth appointment.
Understanding DEXA Scan Results and What Your Numbers Mean
DEXA scan results are reported using something called a T-score, which compares your bone density to that of a healthy 30-year-old adult of the same sex. The T-score is expressed as a number with a plus or minus sign. A T-score of -1.0 or higher indicates normal bone density. A T-score between -1.0 and -2.5 indicates low bone mass, sometimes called osteopenia, which means your bones are less dense than normal but not yet at the threshold for an osteoporosis diagnosis. A T-score of -2.5 or lower indicates osteoporosis.
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The scan also produces a Z-score, which compares your bone density to people of your same age, sex, and body size. While the T-score is used to determine osteoporosis risk, the Z-score helps identify whether bone loss is unusual for your age. If your Z-score is unusually low, your doctor may investigate other causes of bone loss, such as nutritional deficiencies, hormonal imbalances, or medication side effects.
Results typically come back within a few days, and your doctor will contact you with findings. The scan produces images showing your hip, spine, and sometimes your forearm, with different areas color-coded to show density variations. Areas shown in blue indicate normal bone density, while areas in yellow or red suggest lower density. Your radiologist's report will explain what these measurements mean for your individual situation.
It is important to understand that a DEXA scan result does not automatically mean you need medication. Many people with low bone mass never develop osteoporosis or experience fractures. Your doctor will consider your age, sex, other medical conditions, medications, lifestyle factors, and family history when deciding on a treatment plan. Some people benefit from increased physical activity and dietary changes. Others may need medication to slow bone loss. The scan provides information that helps guide these decisions.
Practical takeaway: Your T-score tells you how your bone density compares to healthy young adults, while your Z-score compares you to people your age; both numbers help your doctor determine next steps.
Preparing Your Body: Diet, Exercise, and Health Habits Before Your Scan
While you do not need to make major lifestyle changes days before a DEXA scan, understanding how your daily habits affect bone health helps you interpret results and plan for bone health going forward. Calcium and vitamin D are the two most important nutrients for bone strength. Calcium is the mineral that makes up bone structure, while vitamin D helps your body absorb calcium. The National Institutes of Health recommends that adults ages 51 to 70 consume 1,000 mg to 1,200 mg of calcium daily and 600 to 800 IU of vitamin D daily.
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Common dietary sources of calcium include dairy products, fortified plant-based milks, leafy green vegetables like kale and collard greens, tofu, almonds, and canned fish with bones like salmon and sardines. Vitamin D comes from fatty fish, egg yolks, mushrooms exposed to sunlight, and fortified milk and cereals. About 15 to 30 minutes of sunlight exposure several times weekly also helps your body produce vitamin D naturally. If you have had low calcium or vitamin D intake, this may be reflected in your DEXA results, and your doctor may recommend dietary changes or supplementation.
Physical activity strengthens bones. Weight-bearing exercise like walking, jogging, dancing, or climbing stairs puts stress on bones, which signals them to maintain or build density. Strength training with weights or resistance bands also builds bone strength. The American College of Sports Medicine recommends at least 150 minutes of moderate-intensity aerobic activity weekly, plus strength training at least twice weekly. If you have been sedentary, increasing activity gradually can help improve future bone density.
Other health habits affect bone density over time. Smoking reduces bone density and increases fracture risk, while alcohol use in excess can interfere with calcium absorption and bone formation. Getting adequate sleep—about 7 to 9 hours nightly—supports bone health, as bone remodeling occurs during sleep. While these habits do not need to change for your upcoming scan, understanding their impact helps you work with your doctor on a bone health plan after your results arrive.
Practical takeaway: Adequate calcium and vitamin D intake, regular weight-bearing exercise, and avoiding smoking and excessive