Doctors believe there's an "unusual" Ozempic side effect that could cause false cancer diagnoses.
Weight-loss medications have soared in popularity worldwide, but according to new research presented at the 38th Annual Congress of the European Association of Nuclear Medicine (EANM 2025), they may be causing false cancer warnings on medical imaging scans.
The study reveals that drugs like Ozempic and Wegovy - which are classified as GLP-1 receptor agonists - can interfere with PET-CT scans commonly used to detect and monitor cancer.
The findings raise significant concerns about potential misdiagnoses and unnecessary procedures.
False ‘hot spots’ mistaken for cancer or inflammation
Researchers from Alliance Medical, a leading European imaging provider, examined oncologic FDG PET-CT scans and found “unusual” tracer patterns in patients using GLP-1 drugs such as semaglutide (Ozempic, Wegovy) and liraglutide (Victoza, Saxenda).
Per Business Standard, these patterns, bright spots or “hot spots," appeared in areas like muscles, heart tissue, and brown fat, where doctors don’t typically expect cancer activity.
Because PET-CT scans work by highlighting areas of high sugar consumption, often a hallmark of cancer, GLP-1 drugs, which affect how the body metabolizes sugar, can cause abnormal uptake even when there’s no disease present.
Researchers warned that if a radiologist is unaware that a patient is taking a GLP-1 medication, these altered patterns could be mistaken for cancerous growths, inflammatory disease, or disease progression.
'No guidance' yet on how to interpret scans altered by GLP-1 drugs
“We noticed unusual uptake in one of our patients on a GLP-1 agonist, which prompted a wider review across our network,” said Dr. Peter Strouhal, Medical Director at Alliance Medical and lead author of the study, per The Independent.
“We found that these altered patterns are increasingly common, yet there is currently no national or international guidance in the UK addressing this emerging issue," he added.
Strouhal said "recognizing the characteristic uptake associated with GLP-1 agonists helps avoid unnecessary anxiety and interventions,” adding: “Ensuring patients receive the right care, at the right time, without detours or doubt.”
Despite the risks, researchers do not recommend stopping GLP-1 treatment before scans, as it could disrupt blood sugar or weight control. Instead, the key is communication.
Patients should always inform their medical team if they’re using GLP-1 drugs. Clinicians are urged to carefully document medication history when interpreting PET-CT scans.
Some regions, including Australia, suggest scheduling scans in the morning, fasting from midnight, and ensuring stable blood sugar beforehand.
In the future, the Alliance Medical team plans to expand its research across more imaging centers to strengthen its data and push for international protocols on GLP-1-related scan interpretation.