Since my mom is thought to be allergic to contrast, she gets PET/CT w/o contrast. In which case, it seems like the suggestion is to not take Metformin the morning of the PET.
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Persons with diabetes who are taking metformin (some of the brand names include Glucophage®, Glucovance®, or Metaglip®) must STOP the medication on the day of the exam and 48 hours after receiving intravenous contrast. The combination of the drug with the contrast material that is used for CT scans could cause serious side effects. Be certain to discuss this with your physician.
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Oral Hypoglycemic Agents
- The day before the PET scan Take your usual oral hypoglycemic agents and eat regular meals the day before the PET scan.
- Fast for 12 hours.
- On the morning of the PET scan Do not take your oral hypoglycemic agents.
After the PET scan is done For Metformin (Glucophage, Glucophage XR, Fortamet, Glumetza, Riomet): The PET scan technologist will tell you how and when to resume taking Metformin after the PET scan. If a contrast CT scan is done, do not take Metformin for 48 hours and do not resume taking it before your renal function has been tested and shown to be normal. You will receive instructions about this on the day of your scan.
For oral hypoglycemic agents other than Metformin (see above for brand names): Take your usual oral diabetes medicines with lunch. After this, return to your usual doses.