EANM Guidelines for FDG PET/CT Preparation in Non‑Diabetic Patients

1. Timing and Fasting Requirements

• The European Association of Nuclear Medicine (EANM) recommends a minimum 4‑hour fast before FDG injection for all non‑diabetic patients; fasting time is measured from the moment of injection, not from the appointment time. 1
• For morning scans, patients should stop eating after midnight the night before the exam. 1
• An evening meal should be light, containing only a small amount of carbohydrates (e.g., ≤ 8 g) and no alcohol; the meal must be finished by midnight. 1

2. Dietary Restrictions

• Consuming ≤ 8 g of carbohydrates 12 hours before the scan is acceptable, provided the patient then observes the ≥ 4‑hour fast before FDG injection. 1
• On the morning of the scan, only plain, unflavored water is permitted; coffee, caffeinated beverages, and “sugar‑free” drinks (which may contain trace carbs) must be avoided. 1

3. Hydration Protocol

• Patients should drink approximately 1 L of water within the 2 hours preceding FDG injection to promote hydration and reduce urinary bladder activity. 1

4. Physical Activity and Comfort Measures

• Strenuous exercise should be avoided for at least 6 hours (preferably 24 hours) before the scan to limit muscular FDG uptake. 1
• During the injection and uptake phase, patients should remain seated or recumbent and silent to minimize motion artifacts. 1
• Keeping the body warm for 30–60 minutes before injection helps suppress brown‑fat FDG accumulation. 1
• Patients should void immediately before scanning to reduce bladder activity that could obscure nearby structures. 1

5. Blood Glucose Verification

• Blood glucose must be measured immediately before FDG administration and must be < 11 mmol/L (200 mg/dL) for the scan to proceed; this threshold is rarely exceeded in properly fasted non‑diabetic individuals. 2

6. Special Considerations for Cardiac Imaging

• While standard oncologic FDG PET/CT follows the fasting protocol above, cardiac imaging protocols may require a glucose load 1–2 hours before injection to visualize non‑ischemic myocardium. The fasting regimen remains appropriate for routine oncologic studies. 1

FDG PET/CT Preparation Guidelines for Recurrent Thyroid Cancer Surveillance

Dietary Preparation

• A light evening meal containing minimal carbohydrates (and no alcohol) should be finished by midnight for a morning FDG PET/CT scan; peanuts are acceptable because they are low‑carbohydrate, high‑protein/fat foods【3】.
• For afternoon scans, a light breakfast may be consumed at least 4 hours before the scheduled appointment【3】.

Fasting & Timing

• Patients must observe a minimum 4‑hour fast from the time of FDG injection (no food, simple carbohydrates, or liquids except plain water)【3】.
• The 4‑hour fasting interval is calculated from the injection moment, not from the appointment time【3】.

Hydration

• In the 2 hours preceding FDG injection, ingest approximately 1 liter of plain, unflavored water to dilute urinary FDG and reduce image artifacts【3】.
• Only plain water is permitted during the fasting period; other beverages are prohibited【3】.

Physical Activity & Positioning

• Strenuous exercise should be avoided for at least 6 hours (preferably 24 hours) before the scan to limit muscular FDG uptake【3】.
• During the injection and subsequent uptake phase, remain seated or recumbent and remain silent to minimize motion‑related artifacts【3】.

Temperature Management

• Keep the patient warm beginning 30–60 minutes before FDG injection and throughout the uptake period to suppress brown‑fat FDG accumulation【3】.

Beverage Restrictions

• Coffee, caffeinated drinks, and “sugar‑free” beverages are prohibited because they may contain trace simple carbohydrates or stimulatory compounds that affect FDG distribution【3】.

Intravenous Fluid Restrictions

• Glucose‑containing intravenous fluids must not be administered for at least 4 hours before FDG injection【3】.

Thyroid Cancer‑Specific Indications

• FDG PET/CT is indicated for surveillance of recurrent differentiated thyroid cancer when serum thyroglobulin is rising or structural disease is suspected【4】.

Blood Glucose Monitoring

• Blood glucose is measured immediately before FDG administration; the scan may proceed if plasma glucose is < 11 mmol/L (200 mg/dL)【5】.