DEXA Scan (Dual X-ray Absorptiometry) to Measure Bone Health

Testing your bone density -- how strong your bones are -- is the only way to know for sure if you have osteoporosis. One common test doctors use is called dual energy X-ray absorptiometry (DXA or DEXA).

DXA scanning focuses on two main areas -- the hip and the spine. If you can’t test those, you can get a DXA scan on your forearm. These areas can give your doctor a good idea of whether you’re likely to get fractures in other bones in your body.

What Happens During a DXA Scan?

The scan generally takes 10 to 20 minutes. It’s painless, and the amount of radiation you get from the X-rays the scan uses is low. Unlike some other types of tests, like MRIs or CT scans, you won’t have to lie inside a closed tunnel or ring. Instead, you’ll lie on an open X-ray table and try to stay still as the scanner passes over your body. When the test is over, you’ll be able to go home.

A DXA scanner is a machine that produces two X-ray beams. One is high energy and the other is low energy. The machine measures the amount of X-rays that pass through the bone from each beam. This will vary depending on how thick the bone is. Based on the difference between the two beams, your doctor can measure your bone density.

DXA Scan Results

For the results of your scan, you’ll get a T-score. It shows how much higher or lower your bone density is than that of a healthy 30-year-old, the age when bones are at their strongest. The lower your score, the weaker your bones are:

  • T-score of -1.0 or above = normal bone density
  • T-score between -1.0 and -2.5 = low bone density, or osteopenia
  • T-score of -2.5 or lower = osteoporosis

Sometimes doctors will give you another DXA scan result -- a Z score. It compares your bone density to a normal score for a person of your same age and body size.

Who Should Get a DXA Scan?

The U.S. Preventive Services Task Force says people who should get DXA scans for bone density include:

  • Women ages 65 or older
  • Women ages 60 or older who have a higher chance of getting a fracture

Talk to your doctor about whether the test is a good idea for you.

WebMD Medical Reference Reviewed by Laura J. Martin, MD on September 26, 2016

Sources

SOURCES:

National Osteoporosis Foundation: "Bone Density Exam/Testing."

NHS: "DEXA (DXA) scan -- How it is performed."

U.S. Preventive Services Task Force: "Final Recommendation Statement: Osteoporosis: Screening."

© 2016 WebMD, LLC. All rights reserved.