Ozempic-like medications may trigger false cancer signals on scans

A new study finds that GLP-1 weight-loss drugs such as Ozempic and Wegovy may alter PET-CT cancer scans, raising concerns about false positives and unnecessary treatment risks

Popular weight-loss drugs like Ozempic and Wegovy may interfere with cancer scans, leading to possible misdiagnosis, new research has revealed.

 

The findings, presented at the 38th Annual Congress of the European Association of Nuclear Medicine (EANM 2025), come from a study titled GLP-1 agonists pose emerging challenge for PET-CT imaging. Researchers found that patients on GLP-1 drugs sometimes show unusual patterns on PET-CT scans (the imaging tests often used in cancer diagnosis and staging), where bright spots can be mistaken for cancer or inflammation, raising fresh concerns for both doctors and patients.

False ‘hot spots’ found in patients on GLP-1 therapy

Researchers from Alliance Medical Ltd in the UK found that patients taking GLP-1 drugs sometimes showed abnormal tracer uptake in their muscles, heart, or brown fat. If doctors are unaware of a patient’s medication history, these “hot spots” could be mistaken for cancer, leading to unnecessary biopsies, incorrect staging, or delayed treatment.

 

What are GLP-1 drugs such as Ozempic and Wegovy?

GLP-1 receptor agonists (like semaglutide in Ozempic and Wegovy, or liraglutide in Victoza and Saxenda) were originally developed to treat type 2 diabetes. They mimic a natural gut hormone that lowers blood sugar and slows digestion, while also curbing appetite.

 

Because of their effectiveness in weight loss, prescriptions have skyrocketed. Today, millions of people worldwide use them for either diabetes or weight management.

How GLP-1 drugs interfere with PET-CT cancer scans

A PET-CT scan works by injecting a small amount of radioactive sugar called fludeoxyglucose (FDG) into the body. Since cancer cells consume more sugar than normal cells, they appear as “bright spots” on the scan.

 

However, GLP-1 drugs alter how the body processes sugar and affect muscle, heart tissue, and fat metabolism. As a result, scans may light up in unusual areas, even when there’s no cancer.

 

Dr Peter Strouhal, lead author of the study, said in a statement, “We noticed unusual uptake in one of our patients on a GLP-1 agonist, which prompted a wider review across our network. These altered patterns are increasingly common, yet there’s currently no national or international guidance addressing this issue.”

Why GLP-1 drugs could cause cancer scan misreads

According to the study, the risk of misinterpretation is real. The researchers found that if a radiologist is not aware that a patient is on GLP-1 medication, they might mistake these uptake patterns for: 

• Cancerous growths 
• Inflammatory disease 
• Or even disease progression 

This could lead to unnecessary tests, incorrect cancer staging, and avoidable anxiety for patients. On the other hand, a genuine tumour could be overlooked if the altered uptake distracts attention.

Should you pause Ozempic before a PET-CT scan?

Not at the moment. The researchers do not recommend stopping GLP-1 treatment before scans, as this could interfere with diabetes control or weight management.

 

Instead, the advice is: 

• Always tell your doctor and imaging team if you’re taking a GLP-1 drug. 
• Clinicians should document medication history and interpret scans accordingly. 
• Some countries, like Australia, recommend fasting from midnight, scheduling scans in the morning, and ensuring good blood sugar control.

 

Until official global guidelines are developed, clear communication between patients and doctors is key.

What happens next?

The Alliance Medical research team plans to expand its data collection across more imaging centres to build a stronger evidence base and help establish international guidance for interpreting scans in patients on GLP-1 therapy. 

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