New ‘unusual’ side effect of weight loss drugs becoming more common, research suggests

A new “unusual” side effect of weight loss drugs is becoming more common, research has suggested.

Weight loss medications like Ozempic and Wogovy have skyrocketed in popularity. About one in eight American adults said they took a GLP-1 drug, used to treat type 2 diabetes and obesity, according to a Kaiser Family Foundation survey published in May 2024.

But as with any drug, there are side effects, including a newly found one that could interfere with medical imaging.

Researchers from Alliance Medical, a European provider of imaging services, reviewed FDG PET-CT oncology scans in patients taking GLP-1 medications.

With an FDG PET scan, a patient receives an IV injection of a radiotracer called fluorodeoxyglucose. Diseased cells in the patient’s body absorb more of the radiotracer than healthy ones, and the PET scanner detects these “hot spots,” according to the Cleveland Clinic. Healthcare providers can perform a PET scan and a CT scan, which uses x-rays, at the same time to produce more accurate 3D images.

Alliance medical researchers found several abnormal FDG absorption patterns in patients taking GLP-1 medications, according to a September presentation at the European Association of Nuclear Medicine Annual Congress. These abnormal patterns could be misinterpreted by doctors if a patient’s medication history is not considered.

“We noticed unusual absorption in one of our patients on a GLP-1 agonist, prompting a broader review in our network,” said lead author Dr. Peter Strouhal, chief medical officer at Alliance Medical, in a statement published by the American Association for the Advancement of Science.

“We find that these altered patterns are increasingly common, but there is currently no national or international guidance in the UK that addresses this emerging issue.”

If patients’ scans are misinterpreted, it can lead to unnecessary tests, incorrect cancer staging, and delays in treatment.

“Recognizing the characteristic absorption associated with GLP-1 agonists helps avoid anxiety and unnecessary interventions, ensuring that patients receive the right care, at the right time, without diversion or doubt,” added Dr. Strouhal.

The researchers advise that imaging professionals carefully document patients’ medication history to help avoid these misinterpretations.