AS MORE PEOPLE TURN to Ozempic (semaglutide) and other glucagon-like peptide-1 agonists (GLP-1s) to manage diabetes and support weight loss, some research suggests these medications may change how certain tissues appear on PET-CT scans.
Physicians use PET-CT scans to see whether cancer has spread and how extensive it is. People undergoing these scans receive an IV infusion of a radiotracer, most commonly with fluorodeoxyglucose (FDG). This sugar molecule has a radioactive fluorine attached. Active cells, such as cancer cells, consume sugars like FDG rapidly, which causes these cells to light up on scans. The CT portion of the scan overlays detailed X-ray images of bones, tissues and organs that can help pinpoint the exact location of the increased activity in the body.
Some published case reports have suggested that some people who use GLP-1s may have increased FDG uptake on scans in areas such as skeletal muscle, heart tissue and brown adipose tissue. Research presented at the 38th Annual Congress of the European Association of Nuclear Medicine, held Oct. 4 to 8, 2025, looked at medical records from people on GLP-1s who received PET-CT scans. Researchers found unique FDG uptake patterns in imaging scans, which they noted could, in theory, be mistaken for cancer or inflammatory disease.
The researchers did not recommend that people stop taking GLP-1s before undergoing PET-CT scans, but they stressed that physicians should carefully note GLP-1 use when interpreting scan results.
To help clarify what people taking GLP-1s should know before receiving scans, Cancer Today spoke with David Djang, a nuclear medicine physician at Providence Swedish Cancer Institute in Seattle. Djang, who was not involved in the study, has administered and interpreted PET-CT scans for more than 25 years.
CT: How might GLP-1s interfere with PET-CT scans?
DJANG: GLP-1s help to lower blood sugar and increase insulin after meals. They don’t make the sugar disappear but rather enable insulin to push it into different organ systems—first and foremost, the muscles.
In PET scans, our cameras detect FDG—a modified molecule of sugar, or glucose—by picking up its radioactive shine. Most cancer cells have hit an overdrive switch, and that makes them hungry. They use sugar faster than a normal cell does. On an FDG PET scan, active and living cancer cells light up to reveal their location.
In theory, if GLP-1s are affecting insulin levels and redirecting glucose into muscles, would they change the distribution pattern of FDG on a scan? That’s a reasonable question to ask.
CT: How pronounced is the effect on imaging?
DJANG: It doesn’t seem to really be significant. Last year, a retrospective study looked at people who had undergone FDG PET-CT scans, including 30 who were taking GLP-1s and 30 individuals with similar characteristics who were not. “Prominent muscle uptake” of FDG was visible on the PET scans of five of the people on GLP-1 regimens, compared with two of those who were not taking the drugs. That’s a small change for muscular activity.
In the authors’ opinion, none of those findings changed the final PET scan’s interpretation, which is what actually matters.
CT: Will this change the way you administer PET scans to someone taking GLP-1s?
DJANG: PET scans have been in clinical use since the 1990s, so we’ve been doing them for a long time. One thing to remember is that we’ve always had people with diabetes getting PET scans. If you’re on diabetes medicine, it’s affecting the distribution of your glucose. It’s very common, and it does not cause any problem for our interpretation of PET scans.
If someone with diabetes takes short-acting rather than long-acting insulin, we see a larger change in sugar uptake for a shorter amount of time. In those cases, we do have to alter our protocol. But it’s something we’ve been doing for decades. Compared with that, GLP-1s do have some effect on insulin, but it seems to be a lower amount for a more extended period of time. Our perspective after years of treating insulin-dependent people with diabetes suggests that GLP-1s are not making much of a difference in PET scanning protocol or results.
We’ll keep our eye out for new evidence and respond if somebody raises a bigger concern in the future, maybe with a different type of GLP-1.
CT: Will doctors advise people who are taking GLP-1s to do anything different before imaging?
DJANG: I’ve spoken with many of my colleagues around the country and found that nobody has changed their PET scan protocols for people taking GLP-1s. That said, if you’re on a GLP-1, it wouldn’t hurt to let the PET center know, so when they’re reading the scan, they can have that in mind. If it were me, I wouldn’t worry about it too much.
In fact, I suspect that GLP-1s may actually end up helping us. It’s not uncommon that we see people with diabetes and poorly controlled blood glucose. They arrive after fasting as directed with blood glucose levels reaching 200, 300 or sometimes 400 milligrams per deciliter. Ideally, we like to see blood glucose below 150. GLP-1s were originally developed to help manage diabetes. If more people use them, we’re going to see fewer people with poorly controlled diabetes. That will help the scan quality much more than anything the GLP-1 does to alter it.
This interview has been edited and condensed for clarity.
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