GLP-1 Drugs and Cancer Risk: Do Ozempic, Wegovy and Zepbound Prevent or Cause Cancer?

Last reviewed: October 17, 2026.

Do GLP-1 weight-loss drugs cause cancer, or could they help prevent it? This question has become increasingly important as medications such as semaglutide and tirzepatide are used by millions of people to manage obesity, type 2 diabetes and related metabolic conditions.

The answer requires separating the known relationship between excess body weight and cancer from the still-evolving evidence about GLP-1-based medications themselves. Obesity is an established risk factor for several cancers, but that does not automatically mean that a drug producing substantial weight loss will prevent those cancers.

What the evidence says: Randomized clinical trial evidence available in 2026 has not established that GLP-1 receptor agonists increase or decrease the incidence of most cancers. Some observational research suggests lower rates of several obesity-associated cancers among people prescribed these drugs, but longer follow-up and better-designed studies are needed to determine whether the association is causal.

This guide reviews the evidence, identifies the thyroid cancer warning, explains the possible relationship between weight loss and cancer prevention, and outlines what patients should discuss with their healthcare professionals.

1. What are GLP-1 medications?

Glucagon-like peptide-1 (GLP-1) receptor agonists are medications that mimic the action of the naturally occurring GLP-1 hormone. They influence blood glucose regulation, appetite, satiety and gastric emptying.

• Semaglutide: Sold under brand names including Ozempic and Wegovy, with different approved indications, formulations and dosing regimens.
• Liraglutide: Another GLP-1 receptor agonist used in the management of type 2 diabetes or obesity, depending on the product.
• Tirzepatide: Sold as Mounjaro or Zepbound in the United States, depending on the indication. It activates both GIP and GLP-1 receptors, so it is technically a dual agonist rather than a selective GLP-1 receptor agonist.
• Other GLP-1 receptor agonists: The class also includes medicines such as dulaglutide and exenatide.

These medicines can improve metabolic health and produce clinically meaningful weight loss in appropriately selected patients. However, their established metabolic and weight-management benefits should not be confused with a proven ability to prevent cancer.

2. Which cancers are associated with obesity?

The relationship between obesity and cancer is established independently of the question of whether GLP-1 medicines affect cancer incidence.

The US National Cancer Institute and Centers for Disease Control and Prevention identify multiple cancers associated with overweight or obesity. These include:

• Endometrial cancer.
• Colorectal cancer.
• Esophageal adenocarcinoma.
• Postmenopausal breast cancer.
• Kidney cancer.
• Liver cancer.
• Pancreatic cancer.
• Gallbladder cancer.
• Upper stomach cancer.
• Ovarian cancer, thyroid cancer, meningioma and multiple myeloma, for which the strength and nature of the evidence vary.

Sources: National Cancer Institute: Obesity and Cancer and CDC: Obesity and Cancer.

How might obesity contribute to cancer?

Excess body fat can influence several biological processes associated with cancer development:

• Insulin and metabolic signalling: Insulin resistance and elevated insulin levels may influence cellular growth pathways.
• Chronic inflammation: Excess adipose tissue can contribute to persistent low-grade inflammation.
• Sex hormones: Fat tissue influences estrogen production and availability, which is relevant to certain hormone-sensitive cancers.
• Insulin-like growth factor signalling: Changes in insulin and IGF-related pathways may affect cell proliferation and survival.
• Metabolic dysfunction: Obesity-associated conditions, including type 2 diabetes and metabolic dysfunction-associated steatotic liver disease, may contribute to a wider risk profile.

Because GLP-1-based drugs can reduce weight and improve some metabolic abnormalities, researchers are investigating whether treatment might influence these pathways sufficiently to change cancer incidence. Biological plausibility, however, is not proof of cancer prevention.

3. What does the latest research say about GLP-1 and cancer risk?

Three important evidence streams help explain why the current findings can appear contradictory.

Study 1: Randomized trials published in 2026

Evidence level: Systematic review and meta-analysis of randomized controlled trials.

A meta-analysis published in Scientific Reports on August 27, 2026, included 148 randomized controlled trials involving 168,875 participants. The pooled estimate for overall cancer risk was:

Relative risk (RR): 0.99; 95% confidence interval: 0.92–1.05.

This result did not demonstrate a statistically significant difference in overall cancer risk between GLP-1 receptor agonist treatment and comparator groups.

The confidence interval is compatible with a modest reduction or increase in risk. The study therefore provides reassurance against a substantial short-term overall cancer signal, but does not exclude every possible effect or establish long-term safety for every cancer type.

Source: GLP-1 receptor agonists and risk of cancer: A systematic review and meta-analysis of randomized controlled trials.

Study 2: Annals of Internal Medicine, February 2026

Evidence level: Systematic review of randomized, placebo-controlled trials.

This review evaluated 48 trials involving 94,245 participants and examined individual obesity-related cancer outcomes.

The authors concluded that GLP-1 receptor agonists probably have little or no effect on thyroid, pancreatic, breast and kidney cancer incidence, based on moderate-certainty evidence. Evidence for several other individual cancers was less certain.

Importantly, the trials were not designed primarily to investigate cancer outcomes, and their follow-up periods were relatively short for diseases that can take years or decades to develop.

Source: Ko A. et al. Risk for Cancer With Glucagon-Like Peptide-1 Receptor Agonists and Dual Agonists: A Systematic Review and Meta-analysis. Annals of Internal Medicine, 2026. DOI: 10.7326/ANNALS-25-02237.

Study 3: A 2026 review reporting lower obesity-related cancer risk

Evidence level: Systematic review and meta-analysis combining observational studies and randomized trials.

A review published in Diabetes Research and Clinical Practice in April 2026 included 24 studies involving 3,960,974 patients.

It reported an association between GLP-1 receptor agonist use and lower overall risk of obesity-related cancers within ten years:

Relative risk: 0.70; 95% confidence interval: 0.54–0.89.

The review also reported lower incidence of several individual cancers, including colorectal, endometrial, liver, pancreatic, esophageal, gallbladder and ovarian cancers.

This is an encouraging association, but it should not be interpreted as proof that GLP-1 medicines prevent 30% of obesity-related cancers. The pooled evidence included observational studies, which can be affected by differences in patients' baseline health, diabetes severity, healthcare use, screening, treatment selection and other factors.

Source: Ateiwi Y.A. et al. Glucagon-like peptide-1 receptor agonists and the risk of obesity-related cancers: a systematic review and meta-analysis. Diabetes Research and Clinical Practice, 2026. DOI: 10.1016/j.diabres.2026.113158.

How should these findings be reconciled?

Randomized trials are generally better suited to assessing whether a medicine causes an outcome, whereas large observational studies may be better able to identify uncommon outcomes over longer periods. Neither design is automatically definitive in every circumstance.

When randomized trials do not show a clear reduction in cancer incidence but observational analyses report lower rates, several explanations are possible. The observational association could reflect a genuine long-term benefit mediated by weight loss, differences in the populations studied, residual confounding or a combination of these factors.

The practical conclusion: Current evidence is broadly reassuring regarding overall cancer risk, but claims that GLP-1 medicines prevent obesity-related cancers remain unproven.

4. Does semaglutide or tirzepatide increase thyroid cancer risk?

The thyroid cancer question deserves separate attention because semaglutide and tirzepatide carry a specific warning concerning thyroid C-cell tumors.

In rodent studies, these medicines caused thyroid C-cell tumors. Whether this finding translates into an increased risk of medullary thyroid carcinoma (MTC) in humans remains unknown.

US prescribing information for Wegovy and Zepbound includes the following key precautions:

• These medicines are contraindicated in people with a personal or family history of medullary thyroid carcinoma.
• They are also contraindicated in people with multiple endocrine neoplasia syndrome type 2 (MEN2).
• Patients should be counselled about symptoms that may indicate a thyroid tumor, such as a neck mass, persistent hoarseness, difficulty swallowing or difficulty breathing.

Sources: FDA Wegovy prescribing information and FDA Zepbound prescribing information.

Does this mean GLP-1 drugs cause all thyroid cancers?

No. Medullary thyroid carcinoma is a specific cancer originating from thyroid C cells. It is not the same as papillary or follicular thyroid cancer.

The rodent finding and regulatory warning should be taken seriously, but they do not establish that GLP-1 medicines cause thyroid cancer in humans generally. The 2026 randomized-trial evidence review did not establish an increased thyroid cancer risk, although the available evidence cannot exclude a clinically meaningful effect.

People with a personal or family history of MTC or MEN2 should not use a contraindicated product. Anyone with a thyroid history or concerning symptoms should discuss their circumstances with a qualified healthcare professional.

Routine calcitonin testing or thyroid ultrasound solely because someone takes a GLP-1 medicine has not been established as an effective screening strategy. Testing decisions should be guided by clinical findings and medical advice.

5. Could GLP-1 drugs prevent obesity-related cancers?

There is a plausible biological rationale, but the clinical evidence is not yet sufficient to recommend these medicines specifically for cancer prevention.

Possible indirect benefits

When treatment produces sustained weight loss and improves metabolic health, it may affect some of the processes associated with obesity-related cancer risk:

• Reduced adipose tissue and potentially lower obesity-associated inflammation.
• Improved insulin sensitivity and glucose regulation.
• Changes in sex hormone exposure relevant to selected cancers.
• Improvement in some obesity-related metabolic conditions.

These effects provide reasons to investigate a possible long-term cancer benefit. They do not prove that GLP-1 signalling directly suppresses human tumors or that a medicine produces an additional cancer-prevention benefit beyond its effects on body weight and metabolic health.

Why cancer-prevention claims need long-term evidence

Cancer typically develops over a much longer period than the follow-up available in many drug trials. A study lasting two or three years may be able to identify common adverse effects, but it may be underpowered to detect a small change in the incidence of a particular cancer.

Researchers also need to distinguish the effects of treatment from the effects of weight loss itself, changes in diabetes control, other medications, cancer screening and differences in healthcare access.

Until prospective studies with adequate follow-up provide clearer results, GLP-1 medicines should not be prescribed solely to prevent cancer.

6. Do GLP-1 drugs increase pancreatic or colorectal cancer risk?

Pancreatic and colorectal cancers are frequently discussed in relation to GLP-1 medicines, partly because of biological questions and earlier conflicting research.

Pancreatic cancer

Available randomized-trial evidence has not demonstrated a statistically significant increase in pancreatic cancer incidence. In the 2026 Annals of Internal Medicine review, the pooled odds ratio was 0.84, with a 95% confidence interval of 0.53–1.35.

This does not establish that the medicines protect against pancreatic cancer. The interval includes both possible benefit and possible harm, and the number of pancreatic cancer events in trials is limited.

Colorectal cancer

Evidence is also inconclusive for colorectal cancer. Some observational studies report lower incidence among people prescribed GLP-1 medicines. Earlier randomized-trial analyses produced a possible increased-risk signal, whereas subsequent evidence syntheses have not established a consistent causal relationship.

Differences in study populations, duration of follow-up, event counts and the frequency of diagnostic investigations may contribute to inconsistent results.

What patients should do: Follow recommended colorectal cancer screening according to age, personal risk and local clinical guidance. Taking a GLP-1 medicine should not be regarded as a substitute for screening, and a change in bowel habits, rectal bleeding or other concerning symptoms should not automatically be attributed to medication side effects.

7. What about breast, endometrial and liver cancer?

These cancers are important because obesity and metabolic dysfunction are associated with several of them, although the underlying mechanisms and strength of evidence differ.

• Breast cancer: Obesity is associated with increased risk of postmenopausal breast cancer. Randomized trials have not established that GLP-1 medicines reduce breast cancer incidence.
• Endometrial cancer: Obesity is an important established risk factor. Sustained weight loss may influence relevant hormonal and metabolic pathways, but a specific preventive effect from GLP-1 treatment has not been established.
• Liver cancer: Obesity, metabolic dysfunction-associated steatotic liver disease and related metabolic conditions can contribute to liver cancer risk. Whether GLP-1 medicines reduce liver cancer incidence independently of their metabolic effects remains uncertain.

The distinction is important: a medication may improve a risk factor for cancer without having a proven effect on cancer incidence itself. Longer studies are needed to determine whether improvements in weight, insulin resistance and liver health ultimately translate into fewer cancer diagnoses.

8. Can GLP-1 medicines treat existing cancer or prevent recurrence?

Evidence that these medicines help manage obesity or diabetes should not be extrapolated into a claim that they treat an established malignancy.

Current evidence does not establish GLP-1 receptor agonists or tirzepatide as anticancer treatments. They should not replace surgery, radiotherapy, chemotherapy, immunotherapy, targeted therapy or other treatments recommended for a specific cancer.

There is also insufficient evidence to recommend these medicines specifically to prevent cancer recurrence or improve cancer survival.

For people with active cancer, treatment decisions require additional care. Appetite suppression, nausea, vomiting and weight loss may be problematic for patients who are malnourished, experiencing involuntary weight loss or at risk of cancer-associated cachexia. Treatment should be individualized with the oncology team and prescribing clinician.

Anyone already taking a GLP-1 medicine who receives a cancer diagnosis should not stop or change the dose independently. The decision should account for the cancer, nutritional status, diabetes control, treatment plan and individual benefits and risks.

9. Practical recommendations for patients

If you are considering GLP-1 treatment

• Choose treatment based on an established indication, such as appropriate management of obesity or type 2 diabetes, rather than an unproven cancer-prevention benefit.
• Discuss your personal and family medical history, including any history of medullary thyroid carcinoma or MEN2.
• Maintain appropriate cancer screening based on your age, risk factors and clinical recommendations.
• Use a sustainable nutrition and physical activity plan alongside medication, as appropriate for your circumstances.
• Seek medical assessment for persistent or unexplained symptoms rather than assuming they are harmless medication effects.

If you already use semaglutide or tirzepatide

Current evidence does not support stopping an otherwise appropriate prescription solely because of generalized concerns that GLP-1 medicines cause cancer. Equally, it does not justify continuing treatment for the purpose of cancer prevention alone.

Review your medication with your healthcare professional if your medical history changes, you develop concerning symptoms or you receive a new cancer diagnosis.

10. Frequently asked questions

Does Ozempic cause cancer?

Current human evidence has not established that semaglutide causes an overall increase in cancer incidence. A specific regulatory warning concerns thyroid C-cell tumors observed in rodents, with human relevance unknown. People with a personal or family history of medullary thyroid carcinoma or MEN2 should not use products carrying this contraindication.

Does Wegovy reduce cancer risk?

Wegovy can produce substantial weight loss in eligible patients, and some observational research links GLP-1 medicines to lower rates of obesity-related cancers. However, randomized trials have not established that semaglutide prevents cancer, and it should not be used for that purpose alone.

Does tirzepatide cause thyroid cancer?

Tirzepatide carries a warning based on thyroid C-cell tumors in rodents. Whether the drug causes medullary thyroid carcinoma in humans is unknown. The available clinical evidence has not established a statistically significant increase in overall thyroid cancer incidence.

Can GLP-1 drugs prevent pancreatic cancer?

No preventive effect has been established. Randomized-trial reviews have not demonstrated a statistically significant increase in pancreatic cancer, but the available data also do not prove that these medicines prevent it.

Can GLP-1 drugs help cancer survivors live longer?

This remains an open research question. The effects of these medicines on cancer recurrence, cancer-specific survival and treatment outcomes need to be investigated in appropriate studies. Their role in an individual cancer survivor should be based on established indications and coordinated care.

Should people on GLP-1 medication undergo additional cancer screening?

There is no established general recommendation for extra cancer screening solely because a person takes a GLP-1 medicine. Screening should follow the recommendations appropriate to the person's age, history, risk factors and symptoms. Specific clinical findings may warrant individualized investigation.

Conclusion: Reassuring findings, but cancer prevention remains unproven

The relationship between GLP-1 medicines and cancer is more nuanced than either “these drugs cause cancer” or “these drugs prevent cancer.”

Randomized clinical trials available in 2026 have not established a meaningful overall increase or reduction in cancer risk. Observational studies have reported lower incidence of some obesity-related cancers, creating an important research question but not proof of a protective drug effect.

The thyroid C-cell tumor warning remains a specific prescribing consideration, particularly for people with a personal or family history of medullary thyroid carcinoma or MEN2. It should not be misrepresented as proof that all GLP-1 medicines cause human thyroid cancer.

For now, the most defensible approach is to use these medicines for established indications, maintain appropriate cancer prevention and screening practices, and avoid presenting GLP-1 treatment as a proven cancer-prevention or anticancer strategy.

Medical disclaimer: This article is educational and does not replace personalized medical advice. Medication decisions should be made with a qualified healthcare professional. People with cancer or a history of cancer should discuss weight-management treatment with their oncology and medical teams where appropriate.

References and further reading

1. Ko A. et al. Risk for Cancer With Glucagon-Like Peptide-1 Receptor Agonists and Dual Agonists: A Systematic Review and Meta-analysis. Annals of Internal Medicine. 2026;179(2):216–229. PubMed. DOI: 10.7326/ANNALS-25-02237.
2. Ateiwi Y.A. et al. Glucagon-like peptide-1 receptor agonists and the risk of obesity-related cancers: a systematic review and meta-analysis. Diabetes Research and Clinical Practice. 2026;234:113158. PubMed. DOI: 10.1016/j.diabres.2026.113158.
3. Liang W. et al. GLP-1 receptor agonists and risk of cancer: a systematic review and meta-analysis of randomized controlled trials. Scientific Reports. 2026. Full article.
4. Silverii G.A. et al. GLP-1 receptor agonists and the risk for cancer: a meta-analysis of randomized controlled trials. Diabetes, Obesity and Metabolism. 2025. DOI: 10.1111/dom.16489.
5. National Cancer Institute. Obesity and Cancer Fact Sheet.
6. US Food and Drug Administration. Wegovy prescribing information.
7. US Food and Drug Administration. Zepbound prescribing information.