Glucagon-like peptide 1 (GLP-1) drugs are among the most talked-about medications in recent years. First approved to treat type 2 diabetes, certain GLP-1s are now also powerful tools for weight management.

If you’re living with cancer, you may be wondering if it’s safe to take these obesity drugs during your treatment. That’s a very real concern, and researchers are starting to provide answers. New evidence suggests that these medications may be safe for many people during active cancer treatment. They may also help control blood sugar and possibly lower the risk of cancer coming back. Still, careful monitoring for side effects remains key.

This article explains how these weigh-loss drugs work and why they may matter for people with cancer. We’ll address common safety concerns, including questions about thyroid cancer and overall cancer risk. We’ll also discuss muscle loss and whether these medications could play a role in cancer prevention.

Understanding Why Obesity Drugs Matter for People With Cancer

The U.S. Food and Drug Administration (FDA) has approved some GLP-1 drugs for type 2 diabetes and others for weight loss:

• Semaglutide, a GLP-1 receptor agonist, is the active ingredient in Ozempic and Rybelsus (for type 2 diabetes) and Wegovy (for weight loss).
• Tirzepatide is the active ingredient in Mounjaro (for type 2 diabetes) and Zepbound (for weight loss). It acts on two gut hormones — GLP-1 and glucose-dependent insulinotropic polypeptide.
• Liraglutide, an older GLP-1 receptor agonist, is approved as Victoza for type 2 diabetes and Saxenda for weight loss. Unlike semaglutide and tirzepatide, liraglutide must be taken as a daily injection.

GLP-1 receptor agonists mimic natural gut hormones that signal fullness to your brain. They boost insulin levels and slow how fast the stomach empties, which helps reduce appetite. Research also suggests that GLP-1s may lower inflammation, even beyond their effects on weight loss.

For people going through cancer treatment, this may matter more than you think. Weight gain is common during treatment, especially with steroids, hormone therapies, and reduced activity. At the same time, obesity is linked to at least 13 types of cancer, which make up about 40 percent of cancer cases each year in the United States.

Obesity and related conditions, such as insulin resistance and chronic (long-term) inflammation, are known risk factors for several cancers, including colon cancer. For people managing both diabetes and cancer, or those experiencing significant weight gain during treatment, GLP-1s may offer benefits worth discussing with their healthcare team.

Sorting Out Safety Concerns — Myth Versus Evidence

If you’ve looked into GLP-1 medicines, you’ve likely seen some scary headlines. Let’s take a closer look at what research actually shows about the most common safety concerns.

The Thyroid Cancer Question

You may have seen a “black box” warning about thyroid cancer on these medications. Here’s the background: In animal studies, researchers found a higher risk of a rare cancer called medullary thyroid cancer. GLP-1 medicines affected certain thyroid cells in mice and rats, which led to the warning.

In people, the evidence has been generally reassuring, though not completely conclusive. A 2022 review of studies found no significant increase in thyroid cancer risk among people using these drugs. Another study reported that using GLP-1 medicines for up to five years did not raise the overall risk of cancer compared with another diabetes medication.

To be cautious, these medicines are not recommended for people with a personal or family history of medullary thyroid cancer or a rare genetic condition called multiple endocrine neoplasia type 2.

Pancreatic Cancer Risk

Another concern that sometimes comes up is pancreatic cancer. A 2025 review of studies found no increased risk of pancreatic cancer in people with type 2 diabetes who used GLP-1 receptor agonists compared with other treatments. In fact, one recent study found that GLP-1 use was linked to a lower risk of pancreatic cancer compared with several other diabetes medicines.

The Bottom Line on Cancer Risk

Current evidence does not show that GLP-1s cause most cancers in people. Some studies suggest that these medicines may even be linked to a lower risk of certain cancers, including breast and prostate cancer. Research in recent years has shifted away from fears about causing cancer and toward understanding how to use these medicines safely, including for people undergoing cancer treatment.

Using GLP-1s During Active Cancer Treatment

For people already taking GLP-1s — or considering starting one during cancer treatment — practical questions often come up. Here’s what recent research suggests about outcomes, side effects, and timing.

New Findings on Outcomes and Survival

Some observational (real-world) studies suggest that people with type 2 diabetes who started a GLP-1 medicine around the time they began cancer treatment lived longer than those taking metformin alone. They also appeared to have fewer hospital stays and serious infections.

These studies don’t prove that GLP-1 medicines directly improved survival — they show an association, not cause and effect. Why might there be a connection? Good blood sugar control is especially important during cancer treatment. Research suggests that people with cancer and type 2 diabetes who maintain better blood sugar control may live longer. GLP-1 medications may also help reduce inflammation, which plays a role in both diabetes and cancer.

Management of Side Effects

One concern is adding GLP-1 side effects on top of chemotherapy-related nausea. Common side effects of GLP-1s include nausea, vomiting, diarrhea, constipation, and belly pain.

The safety of GLP-1 medicines during active cancer treatment hasn’t been fully studied. Careful monitoring is important to help avoid digestive problems. If nausea or vomiting prevents you from eating or drinking enough, your healthcare provider may recommend stopping the medication for a while.

Drug Timing and Interactions

GLP-1 medicines slow stomach emptying, so they can affect how quickly some oral medications are absorbed. If needed, your oncology team may adjust your medication timing.

Some early laboratory studies have explored possible anticancer benefits. In lab models, breast cancer and prostate cancer cells exposed to GLP-1 medicines showed slower growth under certain conditions. This research is still in early stages and hasn’t translated into proven benefits in people.

Considerations Before Surgery or Procedures

If you’re scheduled for surgery or a procedure that requires sedation, GLP-1s may need to be stopped temporarily. For daily GLP-1 medicines, this often means holding the dose on the day of the procedure. For weekly injections, the medication is typically stopped one week before.

Because GLP-1 drugs slow stomach emptying, food can stay in the stomach longer than usual. This may raise the risk of aspiration (breathing stomach contents into the lungs) during anesthesia. Always follow your surgeon’s and anesthesiologist’s instructions about medication timing.

Addressing the Muscle Mass Question

One of the most important priorities for people during cancer treatment involves preserving muscle mass. Weight loss may seem beneficial, but not all weight loss is healthy.

Cancer-related cachexia is a serious condition involving unintentional muscle loss that can occur in advanced cancer. Cachexia is driven by inflammation and is very different from GLP-1-related weight loss, which works by reducing appetite and slowing stomach emptying.

Using GLP-1 medicines during cancer treatment requires careful monitoring to avoid too much weight loss or muscle loss. Losing too much muscle can make it harder to tolerate treatment, slow recovery after surgery, and lower quality of life.

When To Stop or Avoid GLP-1s

People with cancer-related cachexia or severe loss of appetite would generally not start — or continue — a GLP-1 medicine. If you are losing weight without trying, can’t eat enough due to treatment side effects, or already have severe muscle weakness, these medicines may not be appropriate.

Working With Your Care Team

Teamwork is essential. Your oncologist should know if you are taking — or considering — a GLP-1 medicine so they can adjust anti-nausea medicines and watch for possible drug interactions. A diabetes specialist can help manage complex blood sugar issues. A registered dietitian can guide you on getting enough protein and preventing muscle loss.

The decision should take into account your cancer type, stage, treatment plan, and personal health goals. Lifestyle changes — including nutrition and physical activity — should also be part of the discussion.

Taking the Next Step

GLP-1s are moving from a “wait and see” approach to potentially helpful tools for some people during cancer treatment. Their benefits for blood sugar control — and possible improvements in outcomes — must be balanced against side effects and keeping muscle mass. There is no one-size-fits-all answer. The right choice depends on your individual situation.

You can start by writing down all your current medicines and noting any weight changes since your cancer diagnosis. Keep track of how you feel after meals and any digestive symptoms. Most importantly, have an open conversation with your oncology team about your goals and whether a GLP-1 medicine fits safely into your treatment plan.

Join the Conversation

On MyObesityTeam, people share their experiences with obesity, get advice, and find support from others who understand.

What is your biggest challenge when it comes to managing your weight or blood sugar during cancer treatment? Let others know in the comments below.