Understanding the emerging imaging challenge with GLP-1 medications
GLP-1 receptor agonists, including popular drugs like Ozempic, Wegovy, and Mounjaro, have transformed weight loss and diabetes management. Yet as usage surged—reported to have risen about 700% in the United States from 2019 to 2023—so have reports of unusual side effects. A less obvious consequence is their potential to interfere with a critical medical tool: PET-CT scans. These scans are a cornerstone in cancer diagnosis, staging, and monitoring inflammatory diseases. New research suggests that GLP-1s may distort the metabolic signals these tools rely on, complicating how clinicians interpret results.
How PET-CT scans work—and why GLP-1 drugs might matter
A PET-CT combines two imaging modalities. The PET component uses a radioactive tracer, typically FDG, which highlights tissues with high metabolic activity. Cancer cells and inflamed tissues often take up more FDG, creating “hot spots” that guide diagnosis and treatment planning. The CT portion provides precise anatomical detail, enabling doctors to locate and characterize abnormalities.
When these images are fused, clinicians get a powerful map of metabolic activity aligned to anatomy. But if a drug changes how tissues absorb FDG or how metabolism appears on the scan, the resulting image can mislead even experienced radiologists.
The new evidence: altered FDG uptake patterns with GLP-1 therapy
In a study led by Dr. Peter Strouhal and colleagues at Alliance Medical in the UK, unusual FDG uptake patterns were observed in patients on GLP-1 receptor agonists. The researchers noted hot spots that did not fit typical cancer or inflammatory patterns. They extended their observations across multiple centers, finding that these altered uptake patterns appear increasingly common among GLP-1 users. Importantly, there are currently no formal guidelines to address this phenomenon on a global scale, which fuels variability in interpretation and care decisions.
Implications for patients, clinicians, and healthcare systems
For patients, the consequences of misinterpreted scans can be significant. False positives may lead to unnecessary biopsies, additional imaging, or invasive procedures. On the other hand, altered signals could mask genuine disease, delaying diagnosis and treatment. Given that cancer incidence is rising in some populations and early detection is often the difference between curable and advanced disease, the stakes are high.
Clinicians face a dual challenge: balancing the clear benefits of GLP-1 therapies for weight management with the need to accurately read imaging studies. The study’s authors emphasize that current practice should not require patients to discontinue GLP-1 medications before scans, as the risk/benefit profile of stopping treatment can be unfavorable. Instead, a more prudent approach involves meticulous documentation of medication history and careful interpretation of imaging results in light of the known pattern shifts associated with GLP-1 therapy.
What’s being done—and what comes next
Presenting at the 38th Annual Congress of the European Association of Nuclear Medicine, the team outlined steps to build a robust evidence base. They plan to expand data collection across more imaging centers and pursue international collaboration to establish consistent, evidence-based guidelines. The overarching goal is to prevent unnecessary testing and ensure timely, accurate diagnoses for all patients, regardless of GLP-1 use.
A practical takeaway for patients and providers
People taking GLP-1 medications should inform every clinician involved in their care about current therapy. Imaging teams, in turn, should annotate scans with notes about GLP-1 use and consider pattern recognition alongside traditional criteria. As research progresses, formal guidelines will likely emerge, helping clinicians distinguish GLP-1-related FDG uptake from pathology more reliably.
Looking ahead
With growing adoption of GLP-1 medications worldwide, the medical community must adapt PET-CT interpretation to preserve diagnostic accuracy. The ongoing international collaboration promises to translate early findings into practical guidelines, protecting patients from delays in care while preserving the therapeutic benefits of GLP-1 therapies.
