What should you know about a DEXA body composition scan?

The scan separates tissues according to how they absorb X-rays, then produces estimates for bone mineral, fat mass and lean soft tissue. Some reports show regional results, such as differences between the arms, legs and trunk. Lean tissue is not the same as pure muscle, because it includes water and other non-fat tissue. Results can be influenced by hydration, recent exercise, food intake, clothing and the scanner's analysis method, so comparisons are most useful when conditions are similar. This assessment is different from a clinical diagnosis and should be interpreted with your history, examination and goals.

Ask the centre whether it wants you to avoid food, strenuous exercise or supplements beforehand, and wear light clothing without metal where possible. Tell staff about pregnancy, recent contrast imaging, implanted devices or difficulty lying still. You will usually lie flat while the scanner passes over you. Keep your body still and breathe normally. If you are tracking training or nutrition changes, use the same preparation and similar timing for future scans so the trend is easier to interpret.

A body composition report is not an emergency test. Arrange medical review for unexplained weight change, persistent weakness, repeated falls, or symptoms such as swelling or breathlessness rather than relying on scan figures alone. Seek urgent help for chest pain, severe breathing difficulty, fainting, or sudden one-sided weakness.

Ask which tissues were estimated, how the centre defines lean mass, whether the findings change your care, and how to compare this report with other measurements such as waist size, strength or blood tests.