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Foods to Eat Before a PET Scan. A PET (positron emission tomography) scan is a powerful process for detecting cancer. Cancer cells grow extremely fast and need a lot of glucose. A doctor will inject the patient with glucose, and the PET scanner detects if any cells are emitting signs of high glucose use. If you eat before your PET scan, you risk throwing your glucose levels off balance and getting inaccurate results.
When you schedule a PET-CT scan, the staff will tell you how to get ready. For example, you might need to drink only clear liquids after midnight the night before the scan. Or you might need to stop eating and drinking at least 4 hours before the scan. Ask a member of your health care team.