Can semaglutide cause cancer? No study in people has shown that it does. Its label carries a boxed warning because it caused thyroid C-cell tumors in rodents, and it is unknown whether that happens in humans. Anyone with a personal or family history of medullary thyroid carcinoma or MEN 2 should not take it.
Written by Kiara DeWitt, BSN, RN
Medically reviewed by Dr. Josh Allen, D.O., Medical Director on October 28, 2026
Medical disclaimer: Medical weight loss treatment is prescribed only after a clinical consultation and is not appropriate for everyone. Whether you are a candidate is decided by a licensed provider, not by any tool or information on this page. Results vary between individuals and depend on adherence, diet, and activity.
Semaglutide’s prescribing information carries a boxed warning, “Risk of Thyroid C-Cell Tumors.” It states that in rodents, semaglutide causes dose-dependent and treatment-duration-dependent thyroid C-cell tumors at clinically relevant exposures. It also states that it is unknown whether semaglutide causes thyroid C-cell tumors, including medullary thyroid carcinoma (MTC), in humans, because the human relevance of the rodent findings has not been determined.
The label lists a personal or family history of MTC, or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), as a reason not to use semaglutide. It also notes that routine monitoring with blood calcitonin tests or thyroid ultrasound is of uncertain value for detecting MTC early.
Semaglutide is the active ingredient in Ozempic, Wegovy, and Rybelsus, according to their FDA prescribing information. The boxed warning applies to all of them.
MTC is a rare thyroid cancer that starts in the C cells of the thyroid, according to the National Cancer Institute, which puts it at 3% to 4% of all thyroid cancers. MEN 2 is an inherited condition that raises the risk of MTC.
There’s no proven link in humans. The label’s thyroid tumor warning comes from rodent studies, and its human relevance hasn’t been determined. Large human reviews and a Scandinavian cohort of 145,410 people found no increase in thyroid cancer, while one French study of GLP-1 medications found a higher risk after 1 to 3 years of use.
The boxed warning comes from studies in rats and mice, not people. The label states plainly that it hasn’t been determined whether those rodent findings apply to humans. That’s why researchers have turned to large human studies for answers.
Four studies give the clearest picture so far:
Taken together, the evidence is reassuring: the largest reviews haven’t found a cancer increase. But results aren’t unanimous, and follow-up is still short. Cancer can take years to develop, and longer studies are still needed.
The label lists acute pancreatitis, inflammation of the pancreas, as a warning. Pancreatitis is not cancer, and the two shouldn’t be confused.
On pancreatic cancer itself, the two large reviews above point the same way. The 2023 meta-analysis found no increase in pancreatic cancer with semaglutide, and the 2026 Annals of Internal Medicine review found GLP-1 medications probably have little or no effect on pancreatic cancer risk. Tell your provider about any history of pancreatitis before starting treatment.
According to the National Cancer Institute, there is consistent evidence that higher amounts of body fat are linked to a higher risk of a number of cancers. That’s one reason weight management matters for long-term health.
That doesn’t mean semaglutide prevents cancer. No study has shown that it does, and it isn’t prescribed for that purpose. Any discussion of cancer risk and weight should stay with your provider and your broader care team.
According to the label, you should not take semaglutide if you:
The label also includes warnings for other conditions, such as pancreatitis and gallbladder problems, which your provider will review with you. For more, read who should not take semaglutide.
InjectCo’s medically supervised weight loss program is nurse-led, under the medical direction of Dr. Josh Allen, D.O. Before anything is prescribed, your full medical history is reviewed, including:
If you’re in active cancer treatment or have a history of pancreatitis, expect a careful evaluation before any decision about starting.
The medication used in our program is compounded semaglutide from a licensed compounding pharmacy. Compounded medications are not FDA-approved. To understand the difference, see compounded vs brand-name semaglutide.
A nurse reviews your thyroid, pancreas and cancer history before anything is prescribed.
Program from $425 a month with home delivery
The label asks providers to tell patients about the symptoms of thyroid tumors. Tell your provider right away if you notice:
These symptoms have many possible causes, but they should always be checked.
No study has shown that semaglutide caused anyone’s cancer. People taking any medication can be diagnosed with cancer, but large reviews, including a 2026 analysis of 48 trials, haven’t found higher cancer rates with GLP-1 medications than with placebo.
There’s no proven link in humans. The label’s boxed warning comes from rodent studies, and a 2024 Scandinavian study of 145,410 people found no increase in thyroid cancer. A 2023 French study of GLP-1 medications did find a higher risk with 1 to 3 years of use, so research continues.
The large reviews haven’t found an increase. The 2023 meta-analysis found no increase in pancreatic cancer, and the 2026 Annals of Internal Medicine review found little or no effect. The label does warn about pancreatitis, which is inflammation, not cancer.
No increase has been found so far. The 2026 Annals of Internal Medicine review found that GLP-1 medications probably have little or no effect on breast cancer risk, with moderate certainty. The trials were short, so longer studies are still needed.
It’s a warning about thyroid C-cell tumors. Semaglutide caused these tumors in rodents, and the label states it is unknown whether it causes them, including MTC, in humans.
People with a personal or family history of medullary thyroid carcinoma, people with MEN 2, and people with a known serious allergy to semaglutide should not take it, according to the label.
No. Tirzepatide is a different medication, but its label carries a similar thyroid C-cell tumor warning. Read more about tirzepatide safety.
Talk through your history with our nurses before you decide.
$425 a month, or $1,800 for a 6 to 8 month program
Dr. Josh Allen, D.O., is InjectCo’s Medical Director. He oversees the clinical standards behind every treatment InjectCo offers and supports its nurse injectors across all nine Texas locations. He earned his Doctor of Osteopathic Medicine at Lake Erie College of Osteopathic Medicine and completed his residency in emergency medicine with Texas A&M.
Dr. Allen earned his Doctor of Osteopathic Medicine at Lake Erie College of Osteopathic Medicine and completed his emergency medicine residency with Texas A&M. As Medical Director, he reviews InjectCo’s treatments, protocols, and patient education content for accuracy and safety across all nine Texas locations.
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