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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.
Fasting Blood Test. If youâve ever had your cholesterol or glucose levels tested before, you know that food and drink intake can affect the outcome of blood tests. That's why a fasting blood test usually requires that you avoid all food and drinks except water for 12 hours before your screening. Itâs also advised that you avoid alcohol for 24 hours before your fasting blood test, as well as any strenuous exercise.