Who should skip Ozempic, and the thyroid signs to watch

Who Ozempic's label says shouldn't take it, the thyroid signs to tell a doctor about, and whether Ozempic-type drugs cause thyroid cancer, from the big studies so far. Sources are linked throughout.

The short version

• Ozempic's label says not to take it if you or anyone in your family has had medullary thyroid cancer, or if you have a condition called MEN 2.
• Tell a doctor if you get a lump or swelling in your neck, hoarseness, trouble swallowing or shortness of breath while on Ozempic. Its label lists these as possible signs of thyroid cancer.
• The warning comes from studies in rats and mice. The label says it isn't known whether the drug causes these tumours in people.
• In 215,824 people with type 2 diabetes, thyroid cancer was about as common within 4 years on Ozempic-type drugs as on another diabetes pill. The small gap could be chance, and it doesn't rule out a rise.
• Other studies disagree. A French study found more thyroid cancer after 1 to 3 years on these drugs, and a Scandinavian one found no clear rise.

Who should skip Ozempic

Ozempic (semaglutide) belongs to a family of drugs called GLP-1 drugs. Its US label says not to use it if you or anyone in your family has ever had medullary thyroid cancer (MTC), a type of thyroid cancer, or if you have an endocrine condition called multiple endocrine neoplasia type 2 (MEN 2) (Ozempic label, FDA). It lists other reasons too, such as a past serious allergic reaction to semaglutide.

Thyroid signs to tell a doctor about

Ozempic's US medication guide tells people taking it to tell their healthcare provider if they get any of these, because they may be symptoms of thyroid cancer (Ozempic label, FDA):

• a lump or swelling in your neck
• hoarseness
• trouble swallowing
• shortness of breath

The label says routine calcitonin blood tests or thyroid ultrasound scans are of uncertain value for catching medullary thyroid cancer early in people on Ozempic, and may lead to procedures people didn't need. It also says a lump found by a doctor or on a scan, or a high calcitonin result, should be looked into (Ozempic label, FDA).

Other GLP-1 drugs have their own labels. If you take a different one, check its label or ask your pharmacist.

Where the warning came from

In mice and rats, semaglutide caused tumours of the thyroid's C cells, and more of them at higher doses and with longer use. The label says it isn't known whether it causes these tumours, including medullary thyroid cancer, in people. It adds that cases of medullary thyroid cancer have been reported in people taking liraglutide, another GLP-1 drug, and that those reports can't show whether the drug caused them (Ozempic label, FDA).

The study of 215,824 people

Researchers took health records of adults with type 2 diabetes who started either a GLP-1 drug or a DPP-4 pill, another kind of diabetes pill, between 2018 and 2022. They matched 107,912 people in each group on age, body weight, health and other drugs, and left out people with recorded thyroid disease or tumours. They followed them for up to 4 years (Hsiao, 2026).

• 209 people on a GLP-1 drug and 225 on a DPP-4 pill were diagnosed with thyroid cancer, about 2 in 1,000 in each group (Hsiao, 2026, table 2). The gap could easily be chance, and the study can't rule out a small rise.
• Some thyroid problems that aren't cancer were recorded slightly more often on GLP-1 drugs. An immune attack on the thyroid (autoimmune thyroiditis) was recorded in 0.49% against 0.39%, one thyroid lump in 2.06% against 1.96%, and several lumps in 1.48% against 1.35% (Hsiao, 2026, table 2).

The authors call these differences small and say they need confirming. People on GLP-1 drugs also had slightly more thyroid blood tests and scans, which can find more problems, so the study doesn't show the drugs caused them.

What the other big studies found

• France. Researchers took 2,562 people with type 2 diabetes who got thyroid cancer, matched them with 45,184 similar people who didn't, and looked back at which drugs each had used. Using GLP-1 drugs for 1 to 3 years came with a 58% higher risk of thyroid cancer, and a 78% higher risk of medullary thyroid cancer (Bezin, 2023).
• Denmark, Norway and Sweden. 76 of 145,410 people who started a GLP-1 drug got thyroid cancer, against 184 of 291,667 who started a DPP-4 pill. People were followed for 3.9 years on average in the GLP-1 group and 5.4 years in the DPP-4 group. The risk wasn't clearly higher on GLP-1 drugs, but the study's range of uncertainty still included a rise of up to 31% (Pasternak, 2024).
• Trials, combined. Across 15 trials with 84,237 people, 28 thyroid cancers were found in people on GLP-1 and similar drugs and 15 in the comparison groups. That gap could be chance, and the reviewers rated the evidence very low certainty because there were so few cancers (Eisa, 2026).

Where to start

• If you or anyone in your family has had medullary thyroid cancer, or you have MEN 2, Ozempic's label says not to take it. Tell your prescriber before starting.
• If you're on Ozempic and notice a lump in your neck, hoarseness that doesn't go away, or trouble swallowing or breathing, tell your doctor.
• On another GLP-1 drug, read that drug's own label for its thyroid warning.

How far to trust these numbers

• None of the three big studies gave people a drug at random. They used health records, so other differences between the groups can remain. The French study started from people with cancer and looked back at their drugs; the other two followed people forward from starting a drug.
• Thyroid cancer can take years to appear. The study of 215,824 people followed them for up to 4 years, and the Scandinavian GLP-1 group for 3.9 years on average, so longer-term risk isn't settled.
• The study of 215,824 people grouped all GLP-1 drugs together and counted diagnoses from health records, which can miss or mislabel some.
• The trials found very few thyroid cancers, too few to settle the question either way.

Sources

• US Food and Drug Administration. Ozempic (semaglutide) injection: prescribing information and medication guide. DailyMed, 2026.
• Hsiao et al. Association of GLP-1 receptor agonist use with thyroid outcomes in adults with type 2 diabetes. Int J Med Sci, 2026.
• Bezin et al. GLP-1 receptor agonists and the risk of thyroid cancer. Diabetes Care, 2023.
• Pasternak et al. Glucagon-like peptide 1 receptor agonist use and risk of thyroid cancer: Scandinavian cohort study. BMJ, 2024.
• Eisa and Barood. Incretin-based therapy and thyroid cancer risk: a systematic review and meta-analysis of randomized controlled trials. AACE Endocrinol Diabetes, 2026.