Does Ozempic Cause Thyroid Cancer? The FDA Warning Explained

Whether Ozempic injection causes thyroid C-cell tumors in people, including a thyroid cancer called medullary thyroid carcinoma (MTC), is unknown. The FDA boxed warning reflects tumors seen in rodents given semaglutide, the active ingredient in Ozempic. Studies in people have found mixed results and cannot tell you your individual risk.

The U.S. prescribing information says not to use Ozempic if you have a personal or family history of MTC or if you have multiple endocrine neoplasia syndrome type 2 (MEN2). Tell your prescriber if either applies, or if you do not know which type of thyroid cancer runs in your family. FDA prescribing information for Ozempic injection, revised May 2026

We wrote this guide for women who use Ozempic injection or are discussing it with a prescriber and want to understand this warning.

What the boxed warning means for you

MTC is a type of thyroid cancer that develops in the thyroid's C cells, which make a hormone called calcitonin. MEN2 is a rare genetic condition that can cause tumors in the thyroid, parathyroid and adrenal glands, and people with it have a higher risk of MTC. If a relative had thyroid cancer, bring the exact diagnosis if you can find it. Knowing the type helps your prescriber apply the warning. A history of thyroid disease or a nodule also belongs in that conversation.

• Before starting: Tell your prescriber about your own thyroid history and any family history of MTC or MEN2. If the details are unclear, tell them what you know and ask which records would help.
• While taking Ozempic: Contact your clinician promptly if you get a lump or swelling in your neck, hoarseness, trouble swallowing or shortness of breath. The Medication Guide says these may be symptoms of thyroid cancer. If you have severe trouble breathing, call 911.
• If a test already found a nodule or elevated calcitonin: Ask your clinician about evaluation of that finding. The label calls for further evaluation if calcitonin is measured and found to be elevated, or if a thyroid nodule is found on exam or imaging. It also says routine calcitonin testing or thyroid ultrasound is of uncertain value for finding MTC early and may increase the risk of unnecessary procedures.

You can find the boxed warning at the top of the prescribing information. Ask your pharmacist for the Medication Guide for your exact product, and read it each time you get a refill because it may contain new information.

This article covers Ozempic injection. Ozempic tablets are a different formulation, and our Ozempic approval history explains how the injection and tablet labels relate. If you take Ozempic tablets, use the tablet prescribing information, revised January 2026. It covers Rybelsus and Ozempic tablets and also carries a boxed warning about thyroid C-cell tumors.

What researchers have found in people

Studies in healthcare records can compare people who started different diabetes treatments. They can detect a possible signal. Differences in who receives a medicine and how often people are examined can affect those comparisons, and uncommon outcomes such as MTC are hard to estimate precisely. The Ozempic label also notes reports of MTC in people treated with liraglutide, another GLP-1 receptor agonist, after that medicine was marketed, and says those reports are not enough to establish or rule out a causal link with GLP-1 receptor agonist use in humans.

• France: In its authors' summary, a 2023 study of French national health insurance data on people with type 2 diabetes found that one to three years of GLP-1 receptor agonist use was associated with a higher risk of thyroid cancer overall and of MTC. It studied the drug class as a whole.
• Scandinavia: A 2024 study in Denmark, Norway and Sweden compared people starting a GLP-1 receptor agonist with people starting a DPP-4 inhibitor, another type of diabetes medicine. Over an average follow-up of 3.9 years in the GLP-1 group, it did not find a substantially increased risk of thyroid cancer, though it could not rule out a small increase. The estimate for MTC was too imprecise to settle the question. Most of the GLP-1 group took liraglutide, people taking semaglutide were followed for about one year on average, and people with genetic syndromes linked to thyroid cancer were not included.
• A later database study: In its authors' summary, a 2026 analysis of the TriNetX health-record database found a higher risk of thyroid cancer among adults with type 2 diabetes who used a GLP-1 receptor agonist than among matched nonusers. In a separate analysis at the three-year mark, the association was weaker and no longer statistically significant. The authors suggested that closer medical checking of people using these medicines may explain the early finding.

These studies address groups of people using several GLP-1 medicines, mostly in diabetes care. They do not isolate a person's risk from Ozempic injection or resolve what happens with longer use. The FDA warning and contraindications remain relevant to the decision with your prescriber.

Questions to take to your prescriber

1. Does my own or my family's history include MTC or MEN2?
2. If I only know that a relative had thyroid cancer, which record would help confirm the type?
3. Do my current symptoms or any thyroid findings need evaluation?
4. Given my medical history and treatment goals, what choices should we discuss?

Bring a short list of your diagnoses and medications, along with any thyroid reports you already have.

This article is for informational purposes only and does not constitute medical advice, diagnosis or treatment. It does not recommend starting, stopping or changing any medicine. Sources checked November 5, 2026.

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