GLP-1 safety information

Last updated July 17, 2026.

This page summarizes the safety information that applies across the GLP-1 class — including semaglutide (Ozempic, Wegovy, Rybelsus), tirzepatide (Mounjaro, Zepbound), liraglutide (Saxenda, Victoza), and dulaglutide (Trulicity). It is a plain-language summary of FDA prescribing information, not a complete list of every risk and not medical advice. Each medication's own page covers drug-specific details and cites its sources. Always read the medication guide that comes with your prescription, and direct questions to your prescriber or pharmacist.

Are GLP-1 medications safe?

The branded GLP-1 medications are FDA-approved, which means their safety was evaluated in large clinical trials — tens of thousands of patients across the class — and continues to be monitored now that millions of people take them. For the right patient, prescribed and monitored by a licensed clinician, they are considered safe and effective. That sentence has two working parts: these are prescription drugs with real risks, genuine contraindications, and side effects that are common enough to expect — which is exactly why they require a prescriber's judgment rather than being sold over the counter. The sections below cover what those risks are.

Boxed warning: thyroid C-cell tumors

GLP-1 medications carry the FDA's most serious warning class. In rodent studies, these drugs caused thyroid C-cell tumors, including medullary thyroid carcinoma (MTC). It is not known whether they cause MTC in humans. Because of this risk:

• Do not use a GLP-1 if you or a family member has ever had medullary thyroid carcinoma (MTC).
• Do not use a GLP-1 if you have Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
• Tell your clinician right away about a lump or swelling in your neck, hoarseness, trouble swallowing, or shortness of breath — possible symptoms of thyroid cancer.

Who should not take a GLP-1

• Anyone with the personal or family thyroid history above (MTC or MEN 2).
• Anyone who has had a serious allergic reaction to that medication or its ingredients.
• People who are pregnant, planning to become pregnant, or breastfeeding — see the pregnancy section below.
• People with a history of pancreatitis, severe gastrointestinal disease (such as gastroparesis), diabetic retinopathy, or gallbladder disease may still be candidates, but need an individualized decision from their clinician.

Serious side effects

These are uncommon, but they are the reasons GLP-1 treatment needs medical supervision. Stop the medication and contact your clinician — or seek emergency care — if you experience:

• Pancreatitis. Severe, persistent abdominal pain that may radiate to your back, with or without vomiting.
• Gallbladder problems. Pain in the upper right abdomen, fever, yellowing of the skin or eyes, or clay-colored stools. Rapid weight loss itself raises gallstone risk.
• Kidney injury. Usually triggered by dehydration from severe vomiting or diarrhea — keep fluids up, especially during dose increases.
• Low blood sugar (hypoglycemia). Mainly when a GLP-1 is combined with insulin or a sulfonylurea. Symptoms include shakiness, sweating, confusion, and rapid heartbeat.
• Severe allergic reactions. Swelling of the face, lips, tongue, or throat; trouble breathing; severe rash.
• Severe stomach problems. GLP-1s slow stomach emptying; rarely this leads to severe gastroparesis-like symptoms or intestinal blockage (ileus).
• Vision changes. People with type 2 diabetes and diabetic retinopathy need monitoring, as rapid blood-sugar improvement can temporarily worsen it.
• Mood changes. The weight-management labels advise monitoring for depression or suicidal thoughts. If they occur, stop and seek help immediately — call or text 988 in the US.

One more to plan ahead for: because GLP-1s slow stomach emptying, tell any surgeon or anesthesiologist you take one before a procedure that requires anesthesia — you may be advised to pause the medication.

Common side effects

Gastrointestinal side effects are the signature of this class: nausea, vomiting, diarrhea, constipation, abdominal pain, and reduced appetite, along with headache, fatigue, and injection-site reactions. They are most pronounced when starting and after each dose increase, and typically ease as your body adjusts — that's why every GLP-1 uses a gradual titration schedule. Each medication page on this site lists its drug-specific rates and coping strategies.

Drug interactions

• Insulin and sulfonylureas. Combining these with a GLP-1 raises hypoglycemia risk; doses often need adjusting.
• Oral medications. Slowed stomach emptying can change how oral drugs absorb. Tirzepatide specifically can reduce the effectiveness of oral birth control — labels advise a barrier backup for four weeks after starting and after each dose increase.
• Other GLP-1s. Never combine two GLP-1 medications, or a GLP-1 with another semaglutide or tirzepatide product.

Give your prescriber a complete list of everything you take, including supplements.

Pregnancy and breastfeeding

GLP-1 medications should not be used during pregnancy — weight loss itself offers no benefit and may harm a developing baby. If you're planning a pregnancy, the semaglutide labels advise stopping at least two months beforehand because the drug clears slowly. If you become pregnant on a GLP-1, stop and call your clinician. Whether these drugs pass into breast milk isn't established; discuss breastfeeding with your clinician.

A note on compounded GLP-1s

Everything above describes the FDA-approved branded medications. Compounded semaglutide and tirzepatide are not FDA-approved — the FDA has not evaluated them for safety, effectiveness, or quality — and vial-and-syringe dosing adds a real risk of measurement errors. If you use a compounded GLP-1, it should come from a state-licensed pharmacy through a legitimate prescriber, with dosing instructions you follow exactly.

Reporting side effects

Report side effects to your prescriber, and to the FDA's MedWatch program at fda.gov/medwatch or 1-800-FDA-1088. If you think you're having a medical emergency, call 911 or go to the nearest emergency room.

Where the details live

Drug-specific safety information — including exact warnings, side-effect rates, and label citations — lives on each medication's page: Ozempic, Wegovy, Rybelsus, Zepbound, Mounjaro, Saxenda, Victoza, and Trulicity. For how we source and verify medical content, see our editorial policy.