What should you know about a DEXA fat scan?

A DEXA fat scan estimates body fat and lean tissue in different parts of the body using low-dose X-rays, while also allowing bone mineral measurement; it is an assessment tool, not a diagnosis by itself. DEXA may also be called dual-energy X-ray absorptiometry or a DEXA scan. The scan can produce a whole-body estimate and show how tissue is distributed between regions such as the arms, legs, trunk, and hips.

The report may describe fat mass, lean mass, and bone mineral density for the measured regions. Lean mass includes tissues such as muscle, organs, and body water, so it is not a direct measurement of muscle strength or fitness. Results can be affected by hydration, recent food intake, movement, clothing, positioning, and the scanner or software used. For that reason, comparisons are most useful when follow-up scans use similar conditions and the same facility. A result does not by itself explain why body composition is changing or determine what treatment you need.

Before booking, tell the imaging team if you may be pregnant, recently had a contrast examination, or have difficulty lying still. Follow the facility's instructions about eating, drinking, and medicines; preparation requirements can vary. Wear clothing without metal fasteners if advised, remove jewellery and other metal objects, and bring details of medicines or relevant medical conditions. During the appointment, you lie on a scanning table while the arm of the DEXA scanner passes over your body. The procedure is non-invasive, and you need to remain still while images are taken. A clinician or radiographer can explain when and how your report will be shared.

A DEXA fat scan is generally arranged as a planned assessment rather than an emergency test. Contact the imaging service if you develop a concern after the appointment, such as a skin reaction from a device used during the visit, or if you were unable to follow positioning instructions. Seek urgent medical help for severe breathing difficulty, fainting, sudden weakness, or chest pain; these symptoms need prompt assessment and should not wait for a scan result. Arrange a clinical review if an unexpected report finding worries you, if your weight or appetite is changing without an obvious reason, or if you are losing strength or mobility.

Ask what the scan is intended to measure, whether a bone-density scan would answer a different question, and which parts of the report matter for your health. You can also ask how to prepare, whether your medicines or recent imaging affect the appointment, when the result will be reviewed, and what change would justify a repeat scan. If the scan is being used to monitor a condition or nutrition plan, ask how the result will fit alongside symptoms, examination findings, strength, and other tests.