GLP-1 Side Effects: What's Common and When to Call Your Provider

Like any prescription medication, GLP-1 medications can cause side effects. This guide summarizes what the manufacturers list in their safety information so you can have a better conversation with your provider. It is not a substitute for the full label or for your clinician's advice.

Common side effects

Wegovy (semaglutide), per NovoCare: nausea, diarrhea, vomiting, constipation, stomach (abdomen) pain, changes in skin sensations, headache, tiredness (fatigue), upset stomach, dizziness, feeling bloated, belching, gas, stomach flu, heartburn, hair loss, and low blood sugar in people with type 2 diabetes.

Zepbound (tirzepatide), per Lilly: nausea, diarrhea, vomiting, constipation, stomach (abdominal) pain, indigestion, injection site reactions, feeling tired, allergic reactions, belching, hair loss, and heartburn.

Both companies note that these lists are not complete. Talk to your provider about any side effect that bothers you or doesn't go away.

Serious side effects listed in the labeling

Both products list the following (details vary by product):

• Possible thyroid tumors, including cancer. Tell your provider if you get a lump or swelling in your neck, hoarseness, trouble swallowing, or shortness of breath.
• Pancreatitis. Stop the medication and call your provider right away for severe stomach-area pain that won't go away, with or without vomiting. The pain may reach your back.
• Gallbladder problems, including gallstones. Call your provider for symptoms such as pain in your upper stomach, fever, yellowing of the skin or eyes, or clay-colored stools.
• Low blood sugar (hypoglycemia), especially if you also take insulin or a sulfonylurea. Signs include dizziness, sweating, confusion or drowsiness, headache, blurred vision, slurred speech, shakiness, fast heartbeat, anxiety, irritability or mood changes, hunger, and weakness.
• Dehydration leading to kidney problems. Diarrhea, nausea, and vomiting can cause fluid loss. Tell your provider right away if nausea, vomiting, or diarrhea doesn't go away.
• Severe stomach problems. Tell your provider if stomach problems are severe or won't go away.
• Serious allergic reactions. Stop the medication and get medical help right away for swelling of the face, lips, tongue, or throat, problems breathing or swallowing, severe rash or itching, fainting or dizziness, or a very rapid heartbeat.
• Changes in vision in people with type 2 diabetes.
• Food or liquid getting into the lungs during surgery or procedures that use anesthesia or deep sedation. Tell every health care provider you take the medication before any procedure.

Additional items by product:

• Wegovy also lists increased resting heart rate. Tell your provider if your heart is racing or pounding for several minutes.
• Zepbound also lists depression or thoughts of suicide. Pay attention to changes in mood, behavior, feelings, or thoughts, and call your provider right away if you notice new, worse, or worrying changes. If you are in crisis in the U.S., call or text 988.

When to get help

• Call 911 or go to the nearest emergency room for signs of a serious allergic reaction, or if you believe you're having a medical emergency.
• Contact your provider promptly for severe or persistent stomach pain, vomiting or diarrhea that won't stop or leaves you unable to keep fluids down, signs of dehydration, a lump or swelling in the neck, hoarseness or trouble swallowing, vision changes, symptoms of low blood sugar, a racing heart that lasts, or new or worsening mood changes.
• Ask your provider about any side effect that bothers you or doesn't go away.

Other things the labels mention

• Other medicines. Wegovy slows stomach emptying and can affect medicines that need to pass through the stomach quickly. Tell your provider about all medicines, vitamins, and supplements you take.
• Birth control pills. Lilly states that birth control pills may not work as well while using Zepbound and that a provider may recommend another type of birth control for 4 weeks after you start and after each dose increase. Talk to your provider before starting.
• Injection technique. Lilly says your provider should show you how to use Zepbound before the first use. NovoCare says not to share a Wegovy pen with anyone, even if the needle is changed.
• Compounded products. The FDA has received reports of dosing errors with compounded products. See FDA-approved vs. compounded GLP-1 medications.

How to report side effects

You can report side effects to the FDA through MedWatch (fda.gov/medwatch) or by calling 1-800-FDA-1088. Your provider and pharmacist can also help.

Questions to ask your provider

1. Which side effects are most likely with my medication and dose?
2. What should I do if I have nausea, vomiting, or diarrhea?
3. When should I call you, and how do I reach you after hours?
4. Do my other medications or conditions change my risk? See who shouldn't take GLP-1 medications.
5. What would make you adjust or stop my treatment?