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GLP-1 drugs can interfere with FDG-PET-CT scans, study says

Taking GLP-1 receptor agonists can cause atypical tracer uptake patterns in the body that could be mistaken for inflammation or cancer in FDG-PET-CT scans.

Alivia Kaylor, MSc
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Published: 10 Oct 2025

GLP-1 receptor agonists may interfere with the interpretation of fluorodeoxyglucose (FDG) positron emission tomography–computed tomography (PET-CT) cancer scans, according to new findings presented this week at the 38th Annual Congress of the European Association of Nuclear Medicine.

A retrospective case analysis of oncologic FDG-PET-CT scans, led by Alliance Medical researchers in the United Kingdom, found atypical tracer uptake in the bodies of patients taking GLP-1 medications that could risk diagnostic accuracy.

Before FDG-PET-CT imaging scans, patients are injected with FDG, a radioactive glucose tracer, to create detailed images that highlight metabolic activity. Because cancer and inflammatory cells consume glucose at faster rates than other cells, they are picked up as bright, active regions.

Results from the study suggest that GLP-1 drugs can alter glucose uptake in muscles, heart tissue and brown fat in ways that mimic these same metabolic patterns, leading to scans resembling disease activity.

The atypical FDG uptake could be mistaken for inflammation or cancer, leading to potential diagnostic errors, incorrect cancer staging, unnecessary testing or delayed treatment if the patient's drug history isn't taken into account, the researchers warn.

"Recognizing the characteristic uptake associated with GLP-1 agonists helps avoid unnecessary anxiety and interventions, ensuring patients receive the right care, at the right time, without detours or doubt," Peter Strouhal, M.D., Ph.D., Medical Director at Alliance Medical and lead author of the study, said in an AAAS news release.

Although this phenomenon has been previously reported in isolated case reports, this retrospective study represents one of the first organized reviews across a large diagnostic imaging network.

Industry implications

According to a BMJ study, GLP-1 medications like semaglutide (Ozempic, Wegovy) and tirzepatide (Zepbound, Mounjaro) have seen a 700% increase in use in the United States alone between 2019 and 2023.

With no signs of demand slowing, these hormone-mimicking drugs have quickly become the go-to solution for managing diabetes and aiding in weight loss.

The researchers said they do not recommend patients discontinue GLP-1 therapy before PET-CT scans and instead advised imaging teams to document medication histories to avoid misdiagnoses.

"These altered patterns are increasingly common, yet there is currently no national or international guidance in the United Kingdom addressing this emerging issue," Strouhal added.

While there are currently no U.S. guidelines that address GLP-1 use before FDG-PET-CT scans, Australian guidance recommends continuing GLP-1 therapy, fasting from midnight, scheduling scans in the morning and maintaining glucose control.

Like any medication, GLP-1 use comes with risks and side effects, ongoing research shows.

Recent studies have linked these drugs to a slightly increased risk of eye disease in patients with type 2 diabetes. GLP-1 medications have also been linked to other vision problems as well as an increased risk of renal, pancreatic and gastrointestinal issues.

As clinical and diagnostic evidence of GLP-1 risks continues to mount, clinicians and regulators will need to follow new data closely and adjust guidance accordingly to ensure accurate care.

Alivia Kaylor is a scientist and the senior site editor of Pharma Life Sciences.

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