Foods to Eat and Foods to Avoid Before a PET Scan
Updated on November 5, 2025
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A positron emission tomography (PET) scan is a diagnostic tool that examines body tissue functioning, such as blood flow, oxygen use, and sugar metabolism, to help doctors diagnose and treat disease.
To conduct a PET scan, a healthcare provider injects a small amount of radioactive glucose into a patient’s vein, which allows extremely small cancerous tumors and changes in the heart and brain to show up on the scan.
It's important to follow the specific pre-PET scan diet your doctor recommends to allow the proper distribution of glucose throughout your body.
Types of PET Scans
There are a few types of PET scans:
A fluorodeoxyglucose (FDG) PET scan is used for heart conditions and the detection of tumors, brain disorders, or infections. FDG is the most common radiotracer used for PET scan injections.
A PET-CT scan is a combined PET and computerized tomography (CT) scan. While PET scans show how tissues and organs in the body are working, CT scans generate 3D images of structures in the body.
Meanwhile, a myocardial perfusion PET stress test, also known as a rubidium or adenosine PET, is used to evaluate blood flow through the coronary arteries to the heart muscle.
Different types of PET scans may require different dietary preparations, so check with your doctor to confirm which type you're scheduled to receive.
Foods to Eat Before a PET Scan
In the 24 hours before a PET or PET-CT scan, it’s recommended that you drink extra fluids, preferably water. Foods to eat beforehand include:
- Protein-rich foods, such as beef, chicken, eggs, ham, pork, raw nuts, turkey, tofu, and unsweetened peanut butter
- Vegetables low in carbohydrates, such as green beans, broccoli, celery, lettuce, spinach, and zucchini
- Dairy products low in carbohydrates, such as butter and hard cheeses
- Condiments low in carbohydrates, such as oil and vinegar
Foods to Avoid Before a PET Scan
For up to 24 hours before a PET or PET-CT scan, avoid sugar, sugary foods, high-carbohydrate foods, and most processed foods. Foods to skip the day before include:
- Grains, including bread and breaded foods, cereals, crackers, oats, pasta, and rice
- Starchy vegetables, such as corn, peas, and potatoes
- Fruits and fruit juices
- Dairy products higher in carbohydrates, like yogurt and ice cream
- High-carbohydrate condiments, such as jams, gravies, and most salad dressings
- High-carbohydrate snack foods, like chips and pretzels
- Candy
- Beverages that contain caffeine
- Alcohol
In addition to avoiding these foods and beverages for the 24 hours before your scan, it’s important to avoid any strenuous activity, such as exercising or heavy lifting, for 48 hours before the scan.
For the eight hours preceding your scan, don’t chew gum or eat or drink anything except water. Hydration is key for optimal test results.
Foods to Avoid Before a Myocardial Perfusion PET Stress Test
If you’re undergoing a myocardial perfusion PET stress test, don’t eat or drink caffeinated products, such as coffee, tea, soda, or chocolate, for 24 hours prior to your appointment. It’s also best to avoid decaffeinated versions of these foods and drinks, because they still contain a small amount of caffeine.
If you're taking beta-blocker or calcium channel blocker medications, consult your doctor well before your scan to discuss when to stop taking these medications.
For the three hours prior to your scan, don’t eat anything or drink anything except water.
PET Scan Preparation and Diabetes
People who have diabetes should consult their doctor about how to prepare for a PET scan at least two weeks before the scan, as changing their diet may also require changing their diabetes medication regimen.
If your blood sugar level is outside a particular range on the morning of your scan, it may need to be rescheduled.
The Takeaway
- For 24 hours before a PET or PET-CT scan, drink extra fluids and consume a protein-rich, low-carbohydrate diet, including foods like meat, eggs, raw nuts, low-carb vegetables, butter, and hard cheeses.
- During this 24-hour period, it’s crucial to avoid all sugar, high-carbohydrate foods, alcohol, and caffeine to prevent interference with the radioactive glucose tracer.
- In addition to dietary restrictions, avoid strenuous activity for 48 hours before a myocardial perfusion PET stress test.
- You should fast, consuming nothing but water, for the eight hours before the procedure.
EDITORIAL SOURCES
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Resources
- PET Scan. Cleveland Clinic. October 19, 2022.
- Ashraf MA et al. Fludeoxyglucose. StatPearls. August 28, 2023.
- PET/CT. Radiology Info.
- Myocardial Perfusion PET Stress Test. Cedars-Sinai.
- PET/CT Scan Preparation Guidelines. Florida Cancer Specialists and Research Institute.
- FDG-PET Scan. Cedars-Sinai.
- Before Your PET Scan. Stanford Medicine Health Care.
- PET/CT FDG Scan for Patients With Diabetes. UW Medicine.
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