Learn About Bone Density Testing Procedures

What Bone Density Testing Measures

Bone density testing, also called a DXA scan or DEXA scan, measures how much mineral content exists in your bones. This test uses low-level X-rays to determine bone strength and assess fracture risk. The procedure looks at the density of minerals like calcium and phosphorus in your skeletal system.

During a bone density test, the scanner passes over different parts of your body—most commonly the hip, spine, and forearm. The machine records how much radiation passes through the bone tissue compared to soft tissue. Denser bones allow less radiation to pass through, which the computer measures and records as a numerical score.

The results use a measurement called a T-score. This score compares your bone density to that of a healthy 30-year-old 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 density, sometimes called osteopenia. A T-score below -2.5 suggests osteoporosis, a condition where bones become brittle and break more easily.

Bone density naturally decreases as people age. Women typically lose bone density faster after menopause due to changing estrogen levels. Men also experience bone loss, though usually at a slower rate than women before age 70. By age 70, bone loss rates become similar between men and women.

According to the National Osteoporosis Foundation, about one in three women and one in four men over age 50 will experience an osteoporosis-related fracture in their lifetime. Bone density testing helps identify people at higher risk before a fracture occurs.

Practical Takeaway: Understanding what bone density testing measures helps you recognize why your doctor may recommend this screening. The test provides specific numerical information about bone strength rather than general statements about bone health.

Types of Bone Density Tests Available

Several different bone density testing methods exist, each with specific uses and advantages. The most common type is the dual-energy X-ray absorptiometry scan, commonly called DXA or DEXA. This test accounts for about 90 percent of bone density tests performed in the United States. DXA scans use two X-ray beams at different energy levels to separate bone mineral density from soft tissue.

Quantitative computed tomography (QCT) represents another option. This test uses a CT scanner to measure bone density in three dimensions. QCT provides more detailed information about bone structure than DXA but delivers a higher radiation dose. Doctors may recommend QCT when they need additional detail or when DXA results are unclear.

Peripheral DXA, often called pDXA, measures bone density in the forearm, wrist, or heel rather than the hip and spine. These machines are smaller and portable, sometimes located in pharmacies or doctor's offices. While convenient, pDXA scans may not provide as much diagnostic information as central DXA scans of the hip and spine.

Quantitative ultrasound (QUS) uses sound waves rather than radiation to measure bone density. This test typically occurs at the heel and produces no radiation exposure. However, ultrasound results cannot be directly compared to DXA results, and this method is less commonly used for diagnosis.

Radiographic absorptiometry (RA) uses standard X-ray machines to measure bone density by comparing bone appearance to a reference standard. This method is less precise than DXA but requires less equipment. It is rarely used today because DXA technology has become widely available.

Most medical organizations recommend central DXA scans of the hip and spine as the standard method for bone density testing. These scans provide the most reliable results and allow doctors to make consistent comparisons over time. Insurance coverage typically includes DXA scans when medical reasons support testing.

Practical Takeaway: Knowing the different testing types helps you understand what to expect if your doctor recommends bone density screening. DXA scanning remains the most common and reliable method for routine bone density assessment.

The Bone Density Testing Procedure Step-by-Step

A bone density test typically takes between 10 and 30 minutes from start to finish. Most of this time involves positioning and scanning rather than preparation. Understanding the procedure helps reduce any anxiety about the test.

When you arrive for your appointment, you will check in and complete paperwork. A technician will ask about your medical history, including any surgeries, medications, and previous X-ray or nuclear medicine procedures. Inform the technician if you might be pregnant, as this affects whether the test should proceed. You will also remove jewelry and metal objects from the area being scanned.

For a standard DXA scan of the hip and spine, you will lie on a flat, padded table. The technician positions your body in a specific way to maintain consistency. For the spine measurement, you may place your feet on a box to flatten your lower back against the table. For the hip measurement, your leg is positioned in a brace. These positions may feel awkward but are necessary for accurate results.

The scanning arm passes over your body while you remain still. You will hear a humming sound and may see a red laser line that helps position you correctly. The arm moves slowly over the area being scanned, typically taking several minutes. You must remain completely still during scanning to ensure clear images.

The technician may scan multiple areas during one visit. A standard bone density test includes scans of the lumbar spine (lower back), the femoral neck (upper thighbone), and the total hip. Some facilities also scan the forearm. Each area takes a few minutes to complete.

After scanning finishes, you can immediately return to normal activities. The entire procedure involves minimal radiation—about one-tenth the dose of a standard chest X-ray. You do not need any special care or recovery time after a bone density test.

Results typically become available within one to two weeks. Your doctor will review the results and discuss what they mean for your bone health. Some facilities provide results on the same day as testing.

Practical Takeaway: Knowing the exact steps of a bone density test removes uncertainty and helps you prepare mentally for the procedure. The test is painless, quick, and requires no recovery time.

Who Should Consider Bone Density Testing

Medical organizations provide guidelines about which people should consider bone density testing. The National Osteoporosis Foundation recommends bone density screening for all women age 65 and older, regardless of risk factors. For men, screening is recommended starting at age 70.

People younger than these ages may still benefit from testing if they have specific risk factors. These factors include a personal history of fractures as an adult, a family history of osteoporosis or fractures, use of medications that affect bone density such as corticosteroids, smoking, excessive alcohol use, low body weight, or inadequate calcium and vitamin D intake.

Women who have gone through menopause but are younger than 65 should discuss bone density testing with their doctor, particularly if they have risk factors. The hormonal changes during menopause accelerate bone loss. Men with risk factors should also consider testing before age 70.

Certain medical conditions increase osteoporosis risk and warrant bone density testing. These include rheumatoid arthritis, type 1 diabetes, hyperthyroidism, chronic kidney disease, and gastrointestinal disorders that affect nutrient absorption. People taking medications for these conditions should discuss bone density screening with their healthcare provider.

The U.S. Preventive Services Task Force recommends screening all women 65 and older and postmenopausal women under 65 with risk factors. They also recommend that men 70 and older be screened. These recommendations are based on evidence about fracture risk and the ability of bone density testing to predict fractures.

Even if you do not currently meet screening guidelines, you may want to discuss bone density testing with your doctor. Conversations with your healthcare provider about personal and family history, lifestyle factors, and medical conditions help determine whether testing makes sense for your situation.

Practical Takeaway: Understanding screening guidelines helps you know when to talk with your doctor about bone density testing. Age and risk factors both play important roles in determining whether testing may be relevant for you.

Preparing for Your Bone Density Test