FAQs about Bone Density Testing

There are only two ways to know whether or not your bones are at risk for fractures. The first way is to break a bone doing something that wouldn’t typically cause a bone to break. Fractures in fragile porous bones can be caused by as little as a cough or sneeze.

The second and preferable way is to get a bone density test. The test can confirm a diagnosis of osteoporosis, literally porous bones. Having osteoporosis means that your bones break down faster than they can rebuild, which causes slow bone loss over time. Osteoporosis is a state where bone fractures are more likely, and addressing underlying causes and considering medications can help reduce your risk of having a fracture in your lifetime. Bone density tests can also help monitor the progress of osteoporosis treatment.

What causes drops in bone density? Many things can cause decreases in bone density. Decreased hormone levels due to aging, menopause, some cancer treatments, organ transplant drugs, and long-term steroid medications all interfere with the bone rebuilding process and can lead to osteoporosis.

What is a bone density test? Bone density tests, sometimes referred to as DXA scans or bone densitometry, use X-rays to measure how many grams of calcium and other bone minerals are packed into a segment of bone. DXA stands for dual energy X-ray absorptiometry. The machine sends two X-ray beams at different peak energy frequencies to the target bones. One peak is absorbed by the soft tissue, the other by bone. When you subtract one from the other, you are left with the bone mineral density. The most common bones tested are the spine, hip, and forearm.

Who should have a bone density test? Your doctor may recommend a scan if:

• You’re a woman whose doctor determines you’re estrogen deficient and at risk for osteoporosis, based on your medical history and other findings.
• Your X-rays show possible osteoporosis, osteopenia, or vertebral fractures.
• You’re taking prednisone or steroid-type drugs or are planning to begin this treatment.
• You’ve been diagnosed with primary hyperparathyroidism.
• You’re being monitored to see if your osteoporosis drug therapy is working.

What will I learn? DXA can measure bone density within 2 – 4 percent, while X-ray alone can only detect bone loss that is greater than 40 percent. Your doctor will review the results with you. A score of -1 or above is normal. A score between -1.1 and -2.4 means that you are at greater risk for fracture, and a score below -2.5 means that you have osteoporosis and are at high risk for fracture. Note that a bone density test can confirm that you have low bone density, but it can't tell you why. To answer that question, you need a more complete medical evaluation.

Does it hurt? No. At SVMC, the test is done in the Breast Health and Imaging Center. It is noninvasive and more accurate than a regular X-ray. It involves an extremely low level of radiation. You discontinue calcium supplements 24 hours before the test. You change into a hospital gown and allow the technologist to position your body to obtain the best scan. It takes just a few minutes.

What does it cost? Not all health insurance plans pay for bone density tests, so ask your insurance provider beforehand if you're covered. Medicare Part B covers DEXA scans once every 2 years for people who meet one of the criteria above.  

If I have osteoporosis, how is it treated? There are prescription medications, hormone therapies, and vitamins available to help strengthen your bones. The medications help slow the rate that bones break down. In some cases, they also help rebuild bone. Lifestyle changes, like increasing exercise and improving nutrition, can help as well.

Amy Freeth, MD, is an endocrinologist at SVMC Endocrinology in Bennington, Vermont.