Subcutaneous injection of semaglutide causes increased muscle uptake of 18F-FDG and reduces the imaging quality of PET/CT: a case report

BACKGROUND: F-FDG uptake, which compromises lesion detectability. CASE PRESENTATION: A 48-year-old male with diabetes presented with "right ear fluid outflow" and underwent a baseline PET/CT scan without recent semaglutide, showing focal uptake in the nasopharynx and lymph nodes without muscular interference. Thirteen months later, he returned with lower back pain. A repeat PET/CT performed on the same day as semaglutide injection showed diffusely elevated muscle uptake, obscuring potential lesions. After discontinuing semaglutide for 6 days, a third scan revealed normalized muscular activity and clear visualization of multiple hypermetabolic lesions. CONCLUSIONS: This is the first report indicating that same-day semaglutide administration can significantly reduce PET/CT image quality by increasing muscle FDG uptake. Clinicians should consider discontinuing semaglutide at least 24 h prior to PET/CT in diabetic patients to ensure diagnostic accuracy.