What Bone Density Testing Is and Why Doctors Recommend It
Bone density testing, also called a DXA scan or DEXA scan, is a medical imaging procedure that measures how much mineral (mainly calcium) is packed into your bones. This test takes pictures of your skeleton and uses special technology to determine the strength and density of your bone tissue. The test can show whether your bones are becoming weaker over time, which helps doctors understand your risk for fractures.
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Your bones are living tissue that constantly breaks down and rebuilds throughout your life. When you're younger, new bone is added faster than old bone is removed, and your bone mass increases. Most people reach their peak bone mass around age 30. After that, bone remodeling continues, but you lose slightly more bone mass than you gain. Bone density testing measures this process and creates a picture of bone health at a specific point in time.
Doctors recommend bone density testing for several reasons. The test can detect osteoporosis before a fracture happens, identify people at high risk for fractures, measure how well osteoporosis medications are working, and monitor bone loss over several years. According to the National Osteoporosis Foundation, approximately one in three women over age 70 and one in five men over age 70 will experience a bone fracture related to osteoporosis. Early detection through bone density testing can help prevent these serious injuries.
The procedure is painless, non-invasive, and involves no needles or injections. It takes about 10 to 30 minutes depending on which bones are being tested. The test uses a very small amount of radiation—less radiation than you receive during a cross-country airplane flight or a chest X-ray. Because of these factors, bone density testing has become a standard screening tool in preventive healthcare.
Practical takeaway: Bone density testing is a straightforward screening tool that takes less than an hour and uses minimal radiation. Understanding what the test measures can help you have informed conversations with your doctor about whether testing might be useful for your health situation.
Who Should Consider Bone Density Testing
Different groups of people may benefit from bone density testing based on their age, sex, and risk factors. The U.S. Preventive Services Task Force (USPSTF) provides recommendations about who should be tested. Women age 65 and older should have routine bone density screening. Men age 70 and older are also recommended to have screening. These age-based recommendations reflect the fact that bone loss accelerates as people get older, particularly women after menopause.
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Postmenopausal women younger than 65 who have additional risk factors should discuss bone density testing with their doctor. Risk factors include a personal history of bone fracture as an adult, a family history of osteoporosis or hip fracture, low body weight, smoking, excessive alcohol use, or use of certain medications like corticosteroids. Women who have gone through menopause experience a rapid drop in estrogen, which causes bone loss to happen more quickly. A woman can lose 10% or more of her bone density in the first few years after menopause.
Men younger than 70 with risk factors should also consider testing. These risk factors include a personal history of fractures, low body weight, a family history of osteoporosis, smoking, and use of certain medications. Additionally, men and women with medical conditions that affect bone health—such as rheumatoid arthritis, chronic kidney disease, or gastrointestinal disorders that affect nutrient absorption—may benefit from bone density testing.
People taking certain medications should discuss testing with their doctor. Medications that can affect bone density include corticosteroids (used for inflammation and autoimmune conditions), some seizure medications, and certain cancer treatments. If you've had an X-ray that showed possible bone loss, or if you have vertebral fractures, bone density testing can provide more detailed information.
Practical takeaway: Consider having a conversation with your doctor about bone density testing if you're over 65, approaching or past menopause, have a family history of osteoporosis, or have other risk factors. Your doctor can help determine whether testing makes sense for your individual health situation.
How the Bone Density Test Procedure Works
A bone density test typically occurs in an outpatient imaging center, hospital, or doctor's office that has the necessary equipment. You'll be asked to wear comfortable, loose clothing without metal fasteners, zippers, or buttons. You may be asked to remove jewelry and other metal objects. Unlike some medical imaging procedures, you don't need to fast or take any special preparation before most bone density tests, though your facility may have specific instructions to follow.
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When the test begins, you'll lie on a padded table while the scanning equipment passes over your body. The most common type of bone density test is a DXA scan, which uses two X-ray beams with different energy levels to create a detailed image of bone density. One beam has higher energy and one has lower energy. The difference in how your bones absorb each beam is used to calculate bone mineral density. The machine takes pictures of your bones without requiring you to be enclosed or stay completely still, though remaining still during the scan produces the best images.
The bones most commonly tested are the hip, spine, and forearm, since fractures in these locations are most common and most serious. A typical bone density test measures the lumbar spine (lower back), the femoral neck (upper thighbone), and the total hip area. Some tests also measure bone density in the forearm. The entire scan usually takes between 10 and 30 minutes, with the actual radiation exposure lasting only seconds to minutes. The amount of radiation used is extremely small—a DXA scan delivers approximately 0.001 to 0.01 millisieverts of radiation, which is much less than a standard chest X-ray.
Some facilities also use peripheral DXA machines, which are smaller devices that test bone density in the forearm or heel. These machines are portable and can be located in doctors' offices or community settings. Results from peripheral testing can help determine whether more comprehensive testing is needed. After your test, you can immediately return to normal activities with no restrictions or recovery time needed.
Practical takeaway: The bone density test is a quick, painless procedure with minimal radiation exposure. Knowing what to expect during the test—wearing appropriate clothing, lying still on a table, and having the scan take about 10-30 minutes—can help you feel more prepared and comfortable during the appointment.
Understanding Your Bone Density Test Results
Bone density test results are reported using a measurement called a T-score. The T-score compares your bone density to the bone density of a healthy young adult. A T-score of -1.0 or above is considered normal bone density. A T-score between -1.0 and -2.5 indicates low bone mass, sometimes called osteopenia. A T-score of -2.5 or lower indicates osteoporosis. These ranges were established by the World Health Organization and are used by medical professionals worldwide.
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Your results may also include a Z-score, which compares your bone density to people of your same age, sex, and body size. While the T-score determines risk category for fractures, the Z-score helps identify whether bone loss is unusual for your age. A significantly low Z-score might prompt your doctor to investigate whether an underlying medical condition is causing bone loss.
Your report will typically include bone density measurements for specific areas tested, usually the hip, spine, and sometimes the forearm. Results may show variation between these sites. For example, you might have normal bone density in your hip but low bone density in your spine. Your doctor interprets your overall results considering all measured sites. If results show low bone density, it doesn't mean you will definitely have a fracture, but it indicates increased risk compared to people with normal bone density.
The report may also include a 10-year fracture risk calculation, often called the FRAX score. This tool considers your age, sex, weight, height, previous fractures, family history, and smoking status along with your bone density results to estimate your probability of having a major fracture within the next 10 years. A doctor uses this comprehensive risk assessment to determine whether bone-protective medication or other treatments should be considered.
Practical takeaway: Your bone density results use a scoring system (T-score) that compares your bones to a healthy young adult's bones. Normal results mean your bones have adequate density; low results indicate increased fracture risk. Your doctor will explain your