A written plan for SGLT2 inhibitors and GLP-1 medicines before an FDG PET-CT scan

The guideline gap. The EANM FDG PET/CT procedure guideline (version 2.0, 2015), the reference for preparing adults, covers fasting, blood glucose, insulin and metformin but not sodium-glucose cotransporter 2 (SGLT2) inhibitors or glucagon-like peptide-1 (GLP-1) receptor agonists. A joint Australian Diabetes Society and Australian and New Zealand Society of Nuclear Medicine guideline for people with diabetes (summarised in 2026) covers oral glucose-lowering medicines; only its summary abstract was read, so what it advises for these classes is not reported here.

What the reports show. In 262 women with breast cancer having FDG PET/CT, thyroid uptake was less frequent and lower in the 55 taking an SGLT2 inhibitor, independent of glucose control (Alanli 2026). In a propensity-matched oncology cohort of 187 pairs from 6,747 scans, heart uptake was absent in 64.7 per cent of those taking an SGLT2 inhibitor against 37.4 per cent of those not (Sperry 2025). For GLP-1 medicines the evidence is case reports: a same-day semaglutide injection was followed by diffuse muscle uptake that obscured lesions, which cleared on a scan after the drug had been stopped for 6 days (Hong 2026), and a second report describes muscle and heart uptake complicating interpretation (Oldan 2024). None of these studies tested a preparation rule.

What this means. Whether to pause these medicines, for how long, and how that weighs against blood glucose on the day, is decided department by department.