GLP-1 side effects are most often digestive, such as nausea, diarrhea, vomiting and constipation, according to the FDA labels for Wegovy®, Zepbound® and the newer pills. The labels also list rarer serious risks, and in November 2026 the FDA added a class-wide warning about a rare cause of sudden vision loss.
What you'll find here
- Side effects of each weight-loss medication, taken from FDA labels and trials.
- FDA safety communications and warnings, summarized and dated.
- The specific risks of compounded and gray-market products.
- New clinical trials explained, with what they can and cannot tell you.
Key safety facts (as of November 2026)
- Boxed warning. GLP-1 weight-loss drugs carry a boxed warning about the risk of thyroid C-cell tumors, and they are contraindicated in people with a personal or family history of medullary thyroid carcinoma (MTC) or MEN 2.
- Serious risks on the labels include pancreatitis, gallbladder disease, severe stomach side effects, kidney injury from dehydration, serious allergic reactions, and low blood sugar when combined with insulin or a sulfonylurea.
- Vision (NAION). On November 9, 2026, the FDA announced it is requiring all GLP-1 receptor agonist labels to warn about a possible increased risk of NAION, a rare eye condition that can cause sudden vision loss in one eye. Our GLP-1 vision loss explainer puts the risk in real numbers.
- Compounded products. The FDA does not review compounded semaglutide or tirzepatide for safety, effectiveness or quality. As of May 31, 2026, it had received 990 adverse-event reports linked to compounded semaglutide and more than 730 linked to compounded tirzepatide.
- Pregnancy. The Wegovy® pill and Foundayo® labels say these drugs may cause fetal harm and should be stopped when pregnancy is recognized. Talk to your prescriber if you are planning a pregnancy.
- Birth control and pregnancy planning. The Zepbound® label advises people using oral hormonal contraceptives to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and after each dose increase. The Wegovy® label says to stop it at least 2 months before a planned pregnancy.
How we read new research
A single study rarely changes medical advice. We say what kind of evidence it is (randomized trial, observational study, FDA safety communication or approval), who was studied, how long, and who funded it, and we grade it with the scale in our methodology.
If you notice sudden vision changes, severe stomach pain or signs of an allergic reaction, contact a healthcare professional right away. Never start, stop or change a medication without your prescriber.
For how the oral options compare on side effects and label warnings, read Foundayo vs Wegovy pill. For what each program actually ships (brand-name or compounded), check the price tracker. Our sourcing rules are in the methodology, and our medical disclaimer explains the limits of this information.
Coming next
- Is compounded semaglutide or tirzepatide safe and legal in 2026?
- Retatrutide: status and gray-market risks
