What is dual energy X-ray absorptiometry (DXA)?

The most accurate test for detecting osteoporosis and other bone diseases is dual-energy X-ray absorptiometry (DXA). This test, which takes about 10 to 15 minutes, measures the bone loss in your hips and spine. It also helps your doctor determine how quickly you are losing bone density and predict your risk of fracture. The test is also used to follow the course of the disease and observe the effects of various treatments.

Before your DXA test. You do not have to change your daily routine before this test. Eat, drink, and take your medicines as you normally would. However, do not take calcium supplements (such as Tums) for 24 hours before your bone densitometry test. If you think you might be pregnant, tell your doctor. Also, do not take multivitamins that contain calcium for 24 hours before the test.

During the test. You must wear a hospital gown. You will be asked to lie on your back while the technologist performs the test. There are no needles or injections in this test. The DXA procedure is similar to having a standard X-ray. The amount of radiation used is very small.

After the test. Generally, you can resume your usual activities immediately. The results of your test will be reviewed by a specially trained technologist and certified doctors. Your test results will be provided to your doctor, who will discuss the results with you.

Other information. Retail stores sometimes sell a version of the DXA machine that measures bone mass in your forearm, or ultrasound of the heel. However, these readings do not reflect the bone loss in your hips and spine, where the most common debilitating (disabling) fractures occur. Medicare covers bone density testing for many patients, as required in the Bone Mass Measurement Act of 1998.

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