Unusual side effect of weight loss drugs revealed
Ed Milner | Last update: 10th October 2025
A new study has found that weight loss drugs like Mounjaro and Wegovy may create unusual patterns in cancer scans. This potentially leads to confusion if imaging teams aren’t aware the patient is taking them
What’s going on?
A study from Alliance Medical, a leading imaging provider in Europe, has revealed that people taking GLP-1 weight loss drugs, such as Mounjaro, Ozempic and Wegovy, may show unusual patterns on PET-CT scans.
Read the full summary from News Medical
These scans are often used to help detect cancer or inflammation, using a radioactive glucose tracer (FDG) that shows where energy is being used in the body. But GLP-1 drugs change how the body processes glucose, and that can lead to:
- Unusual uptake in muscles, the heart, or brown fat
- Scan results that look like disease, but aren’t
What does it mean for patients?
These patterns do not mean there is something wrong, but if imaging teams aren’t aware of the medication, they may mistake the scan results for cancer or another condition.
This can lead to:
- Unnecessary further tests
- Delayed treatment
- Stress and confusion for patients
That’s why researchers are urging healthcare professionals to check medication history carefully.
No need to stop your medication
At this stage, no changes are recommended for anyone using these drugs:
- Keep taking your medication as prescribed
- Let your doctor or scan team know you’re using a weight loss drug
- If you’re having a PET-CT scan, it helps to fast overnight and schedule for early morning
Australian guidance already advises some of these steps, but there’s no official UK guidance yet.
Our view
This is a good example of how growing use of weight loss drugs is shaping new medical knowledge. It’s not about panic, it’s about making sure your doctors have the full picture.
If you’re on Mounjaro or Wegovy and booked for a scan just let your medical team know. It could save you time, worry and unnecessary follow ups.
Read more on side effects in our article here.