When the Scan Lies: GLP-1s and False Cancer Readings
New research shows our favorite medications can light up cancer scans even when nothing is wrong.
If you or someone you love have ever had a PET scan to check for cancer, you know firsthand how brutal the wait can be. The fear. The what-ifs. Now imagine getting that call saying, “Something lit up on your scan,” only to later learn that it was just your GLP-1 doing its thing.
That’s what researchers are starting to see with GLP-1 drugs like Mounjaro, Zepbound, Wegovy, and Ozempic. A new study presented at the European Association of Nuclear Medicine’s 2025 conference found that our favorite medications can sometimes make PET-CT scans look abnormal even when nothing is wrong.
PET-CTs are often used to look for cancer, but they’re also used to check inflammation and to see how organs like the heart or brain are working. The test uses a small amount of radioactive sugar to show which areas of the body are burning the most energy. Since cancer cells use more sugar than normal cells, they tend to light up brightly on the image. But GLP-1 medications change how your body handles sugar, energy, and digestion, and that can affect how these scans look.
When the Picture Lies
Researchers from Alliance Medical in the UK noticed something odd in patients taking GLP-1s. Their scans showed glowing areas in places that shouldn’t light up, like muscles, heart tissue, and even brown fat, the kind of fat that burns energy instead of storing it.
If a radiologist doesn’t know someone is on a GLP-1, those spots can easily be mistaken for cancer or inflammation. That can lead to extra tests, false alarms, and a lot of unnecessary fear.
Dr. Peter Strouhal, the study’s lead researcher, said it started with one patient. His team noticed an unusual pattern, reviewed other cases, and realized it wasn’t a one-off. These “false positives” are showing up more and more as GLP-1 use skyrockets. Between 2019 and 2023, it’s estimated that prescriptions for GLP-1 drugs has increased more than 700% in the U.S.
Reading Between the Lines of the Scan
This isn’t suggesting that you stop your medication. The researchers are not recommending or implying that. They just want imaging centers to start asking about GLP-1 use and include it in the scan notes so doctors interpret the results correctly.
Think about that. A simple note in your chart that says “patient on GLP-1” could save you from a cancer scare, a biopsy, or weeks of sleepless nights.
It’s also a reminder that we’re part of something much bigger than just weight loss. These medications are changing how food hits our brains, how our hearts handle stress, how our livers heal, and now even how we see disease on a screen.
The Weight of the System, Seen in a Scan
If you’re on a GLP-1 and you’re getting a PET or PET-CT scan, tell your doctor. Tell the imaging team. Tell the person who preps you. Reference this article. Make sure it’s in the notes. You’re not just protecting yourself, you’re helping the system learn what this new era of medicine really looks like.
Read the original report here: Healthcare in Europe: “GLP-1 Agonists and the Altered Images of FDG PET-CT”
Very good to know.