What should you know about an FDG tracer PET scan?

FDG is a glucose-like radiotracer. Cells that use more glucose can collect more FDG, creating areas that appear more active on the PET images. The CT part supplies detailed body anatomy, while PET adds information about activity. Increased uptake can occur with cancer, but infection, inflammation and normal organs may also take up FDG. A scan therefore supports interpretation alongside symptoms, examination and other tests; it does not by itself confirm a diagnosis.

Clinicians may use this examination to look for a suspected tumour, assess known disease, check lymph nodes or search for a primary site when cancer has been found elsewhere. Results are interpreted by a specialist and shared with the treating team.

Follow the imaging centre’s instructions about fasting, water, medicines and diabetes care. Tell the team if you have diabetes, may be pregnant, are breastfeeding, or have recently had an infection or strenuous exercise. Wear comfortable clothing and remove metal items when asked. After the tracer is given, rest quietly while it distributes; movement and talking may be limited before imaging. The scan itself requires you to lie still, and the team can explain each stage.

Drink fluids after the appointment if your clinician says this is suitable. Ask when you may resume normal meals, medicines and activities.

Contact the imaging team before the appointment if fasting or diabetes instructions are unclear, or if you have difficulty lying flat. Tell staff promptly during or after the scan about dizziness, feeling faint, pain at the injection site, or a new rash or breathing difficulty. These symptoms are uncommon but need immediate attention. Seek urgent help for severe breathing difficulty, swelling of the face or throat, or collapse.

Ask what the scan is intended to answer, whether the examination covers the whole body or a selected region, how diabetes medicines should be managed, and when the report will be discussed. You can also ask whether another test or a tissue sample may be needed to explain an area of increased uptake.