Can Ozempic Fight Cancer? The Evidence Is Not There Yet, Expert Warns
In the span of just a few years, a class of drugs originally developed for type 2 diabetes has been credited with transforming obesity treatment, reducing heart attack risk, and even curbing addiction. Now, a new wave of headlines is asking whether GLP-1 drugs like Ozempic, Wegovy, and Mounjaro can prevent or treat cancer. It is a tantalizing possibility, and one that, according to a leading physician-scientist, remains almost entirely unproven.
“The excitement around the idea that GLP-1 drugs can prevent cancer is running well ahead of the evidence,” wrote Dr. Ziyad Al-Aly, a clinical epidemiologist at Washington University in St. Louis, in a recent analysis published by The Conversation and republished by Live Science. “Not wrong, necessarily. Just not yet earned.”
Al-Aly’s caution comes at a moment of intense public and scientific interest in GLP-1 receptor agonists. More than a dozen observational studies published since 2024 have reported lower cancer rates among users of the drugs. One 2024 study tracking 1.6 million people with type 2 diabetes found that 10 out of 13 obesity-related cancers were less common in GLP-1 users than in those taking insulin. A 2025 analysis of roughly 87,000 adults reported overall cancer rates about 17 percent lower among GLP-1 users, with the clearest reductions in endometrial, ovarian, and meningioma cancers. Another study presented at the 2026 American Society of Clinical Oncology meeting found a 34 percent lower risk of death across six cancer types among GLP-1 users.
But Al-Aly argues that these results are far easier to misinterpret than they first appear. The core problem, he says, is that cancer is more than 100 distinct diseases, a single drug cannot have a single verdict on cancer risk. It may lower some, raise others, and leave most untouched.
The Healthy User Problem
The most serious confounder in the existing research is what epidemiologists call healthy user bias. People who start GLP-1 drugs tend to be healthier and wealthier than those who do not. They have insurance, regular medical visits, and the means to afford expensive medications. Those advantages, not the drug itself, may be what lowers their cancer risk.
This bias is notoriously difficult to remove from observational studies. Al-Aly points to one telling clue: when researchers compared GLP-1 users to patients taking metformin, the standard first-line diabetes drug, the apparent cancer benefit largely disappeared. “The apparent benefit came from the comparison drug, not the GLP-1 drug,” he wrote.
The timing of the reported effects raises further suspicion. Cancer typically takes years or decades to develop, yet some studies have shown apparent cancer reduction almost immediately after patients started taking GLP-1 drugs. “When cancer risk appears to drop almost as soon as a patient starts treatment, the speed is not a magical triumph,” Al-Aly wrote. “It is the tell: people who start these drugs were already at lower cancer risk.”
What the Gold Standard Shows
Randomized controlled trials, the gold standard of medical evidence, paint a much more cautious picture. Two 2025 meta-analyses covering roughly 50 and 48 trials respectively found little evidence that GLP-1 drugs either raise or lower cancer risk. These analyses are more reliable than observational studies, but they inherit their own limitations: short follow-up periods of one to two years and too few cancer cases to settle the question definitively.
A truly definitive trial would need to enroll tens of thousands of participants and follow them for many years. In the meantime, researchers are designing observational studies that emulate randomized trials to get as close to that standard as possible.
The Known Unknowns
Even if GLP-1 drugs do affect cancer risk, researchers have no idea how. The effect could come from weight loss, metabolic improvement, direct anti-inflammatory or immune effects, or an entirely unknown mechanism. Without understanding the pathway, it is impossible to predict which cancers might be affected and which patients might benefit.
Meanwhile, the initial safety concern that launched this field of inquiry, that GLP-1 drugs might themselves cause cancer, appears to have been overstated. A 2025 analysis of 62 studies found no consistent increased risk of pancreatic cancer. Another analysis of 93 clinical trials found no clear link to thyroid cancer in humans, although a U.S. Food and Drug Administration black box warning remains in place based on rodent studies.
“The reassurance is real but provisional,” Al-Aly wrote. “These drugs are young, and cancer can take decades to surface.”
A Hypothesis Worth Testing
Almost all of the existing research comes from a handful of high-income countries, even as GLP-1 uptake becomes global and the cancer burden disproportionately affects lower-income nations. Geographic and demographic limitations mean that even the most robust observational findings may not generalize.
Al-Aly’s bottom line is characteristically direct. “The idea that GLP-1 drugs lower cancer risk is a hypothesis worth testing but not a conclusion to act on,” he wrote. “The surest thing I can say is also the least satisfying: it is still too early. These drugs are far younger than the cancers they are being credited with preventing.”
Sources
[1] Al-Aly, Z. “Can Ozempic prevent or treat cancer? It’s way too soon to say, an expert cautions.” Live Science, 19 July 2026. https://www.livescience.com/health/medicine-drugs/can-ozempic-prevent-or-treat-cancer-its-way-too-soon-to-say-an-expert-cautions