If you and your clinician are talking about a GLP-1 medicine, it is normal to wonder about side effects. The best place to start is the official FDA prescribing information, often called the label. This guide walks through what the labels for semaglutide (Wegovy®) and tirzepatide (Zepbound®) list, and offers questions you can bring to your clinician.
This article is for general education. It does not list every possible side effect. Your medicine comes with its own Medication Guide, and your clinician and pharmacist can answer questions about your situation.
Commonly reported side effects
Most of the common side effects on these labels involve the digestive system. The Wegovy® label lists the most common side effects, reported in 5% or more of patients in studies. They include:
- Nausea, vomiting and diarrhea
- Constipation
- Stomach (abdominal) pain and bloating
- Headache, tiredness and dizziness
- Indigestion, burping and gas
- Acid reflux
The Zepbound® label lists nausea, diarrhea, vomiting, constipation, stomach pain, indigestion, injection site reactions, tiredness, allergic reactions, burping, hair loss and acid reflux as its most common side effects.
MedlinePlus, from the National Library of Medicine, lists similar common side effects for both medicines. If a side effect bothers you or does not go away, tell your clinician.
The boxed warning about thyroid C-cell tumors
Both labels begin with a boxed warning titled "Risk of Thyroid C-Cell Tumors." Here is what it says, in plain terms:
- In studies in rodents, semaglutide and tirzepatide caused thyroid C-cell tumors.
- It is not known whether these medicines cause these tumors, including a type of thyroid cancer called medullary thyroid carcinoma (MTC), in people.
- People with a personal or family history of MTC, or who have an endocrine condition called Multiple Endocrine Neoplasia syndrome type 2 (MEN 2), should not use these medicines.
The Medication Guides ask you to tell your health care provider if you get a lump or swelling in your neck, hoarseness, trouble swallowing or shortness of breath. These may be symptoms of thyroid cancer.
Other serious side effects on the labels
The labels also describe serious risks that are less common. According to the Medication Guides, these include:
- Inflammation of the pancreas (pancreatitis). Watch for severe pain in your stomach area that will not go away, with or without vomiting. The pain may spread from your abdomen to your back.
- Gallbladder problems. Signs can include pain in your upper stomach, fever, yellowing of your skin or eyes, and clay-colored stools.
- Dehydration leading to kidney problems. Diarrhea, nausea and vomiting can cause a loss of fluids. The guides say it is important to drink fluids to help lower this risk.
- Severe stomach problems. Tell your provider if stomach problems are severe or do not go away.
- Serious allergic reactions. Signs include swelling of the face, lips, tongue or throat, trouble breathing or swallowing, severe rash or itching, fainting or feeling dizzy, and a very rapid heartbeat.
- Low blood sugar. The risk is higher in people with type 2 diabetes who also take insulin or a sulfonylurea.
- Vision changes in people with type 2 diabetes.
- A faster resting heart rate. The Wegovy® guide says to tell your provider if you feel your heart racing or pounding for several minutes.
The labels also warn about pulmonary aspiration, which is when food or liquid gets into the lungs, during surgery or procedures that use general anesthesia or deep sedation. Tell every care team about your medicine before any planned procedure.
When to seek help right away
If you have signs of a serious allergic reaction, such as trouble breathing or swelling of your face or throat, call 911 or go to the nearest emergency room. For severe stomach pain that will not go away, the Medication Guides say to stop using the medicine and call your health care provider right away. If the pain is sudden or extreme, seek emergency care. Do not wait for a scheduled visit.
A few other things the labels mention
- Other medicines. These medicines slow stomach emptying, which may affect how your body absorbs medicines you take by mouth.
- Birth control pills. The Zepbound® label advises people who use birth control pills to switch to a non-oral method, or add a barrier method, for 4 weeks after starting and for 4 weeks after each dose increase.
- Pregnancy. Both labels say these medicines may cause harm to an unborn baby. The Wegovy® guide says to stop it 2 months before you plan to become pregnant.
- Not with other GLP-1 medicines. Both labels say not to use them with other GLP-1 receptor agonists.
Questions to ask your clinician
Bringing a short list to your visit can make the conversation easier. Here are some ideas:
- Which side effects are most likely for me, and how can I manage them?
- Does anything in my personal or family history, such as MTC or MEN 2, make the boxed warning matter for me?
- I have had pancreas, gallbladder or kidney problems in the past. Does that change things?
- Could this medicine affect anything else I take, including birth control pills or diabetes medicines?
- What should I do if I have nausea, vomiting or diarrhea that does not go away?
- I have a surgery or procedure coming up. What should I tell that care team?
- Which signs mean I should call you, and which mean I should seek emergency care?
- Is the medicine you are prescribing FDA-approved or compounded?
At Talvi, a licensed clinician reviews your health history before anything is prescribed. Sharing your full history, including family history and every medicine and supplement you take, helps your clinician weigh these risks with you.
Reporting a side effect
You can report a side effect to the FDA through its MedWatch program or by calling 1-800-FDA-1088. You can also tell your clinician, who can help you decide on next steps.
The bottom line
The most commonly reported side effects of semaglutide and tirzepatide involve the stomach and digestion, such as nausea, diarrhea, vomiting and constipation. Both labels carry a boxed warning about thyroid C-cell tumors seen in rodents, and both list other serious risks to watch for. Reading your Medication Guide and talking openly with your clinician are the best ways to understand what these risks mean for you.