If you he diabetes, the American College of Radiology advises medical teams to schedule your PET scan for early in the morning, when your glucose level is lowest.
You should take your insulin the day before your scan. But do not take an insulin injection the morning of the scan.
You can take oral medications as usual. If you take metformin, though, your doctor may ask you to stop taking it 48 hours before your scan.
If you use an insulin pump, turn it off 4 hours before the scan.