GLP-1 Side Effects: What the Labels Report
The figures below come straight from the Wegovy and Zepbound prescribing information. They show how often common effects occurred in each drug's weight-loss trials. They are not a ranking and not a prediction for you.
How often common side effects occurred
Wegovy figures are for the 2.4 mg dose versus placebo. Zepbound figures show the range across the 5 mg, 10 mg and 15 mg doses, with the placebo rate from the same pooled trials.
| Reaction | Wegovy 2.4 mg % | Wegovy placebo % | Zepbound % | Zepbound placebo % |
|---|---|---|---|---|
| Nausea | 44 | 16 | 25-29 | 8 |
| Diarrhea | 30 | 16 | 19-23 | 8 |
| Vomiting | 24 | 6 | 8-13 | 2 |
| Constipation | 24 | 11 | 11-17 | 5 |
| Abdominal pain | 20 | 10 | 9-10 | 5 |
| Dyspepsia | 9 | 3 | 9-10 | 4 |
| Fatigue | 11 | 5 | 5-7 | 3 |
| Dizziness | 8 | 4 | 4-5 | 2 |
| Eructation (burping) | 7 | <1 | 4-5 | 1 |
Different trials, patients and durations: do not compare the two drugs from this table. The Zepbound label also lists injection site reactions (6-8%), hair loss (4-5%) and gastroesophageal reflux disease (4-5%). The Wegovy label also lists headache, hair loss and reflux among reactions at 5% or more.
Boxed warning
Both labels warn about thyroid C-cell tumors. In rodents the drugs caused these tumors; it is unknown whether they do in humans, including medullary thyroid carcinoma. Neither drug should be used with a personal or family history of medullary thyroid carcinoma or with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).
Other warnings on the labels
Both labels carry a Warnings and Precautions section. The headings that appear on one or both include:
- Thyroid C-cell tumors (boxed warning)
- Acute pancreatitis
- Acute gallbladder disease
- Hypoglycemia, mainly with insulin or an insulin secretagogue
- Acute kidney injury from volume depletion
- Severe gastrointestinal adverse reactions
- Hypersensitivity reactions
- Diabetic retinopathy complications in type 2 diabetes
- Pulmonary aspiration during general anesthesia or deep sedation
- Never share a pen between patients
Other points the labels make
- Zepbound delays gastric emptying and can change how well oral medicines are absorbed. For women using oral birth control, the label advises switching to a non-oral method, or adding a barrier method for 4 weeks after starting and after each dose increase.
- The Zepbound label says the drug may cause fetal harm and to discontinue it when pregnancy is recognized. Ask your prescriber about pregnancy plans before starting either drug.
- Tell every clinician about planned surgery or sedation. Both labels warn about pulmonary aspiration under anesthesia.
- Report side effects to the FDA MedWatch program or the manufacturer.
Frequently asked questions
What are the most common GLP-1 side effects?
Stomach and digestive effects. The Wegovy label lists nausea, diarrhea, vomiting, constipation and abdominal pain among its most common reactions, and the Zepbound label lists the same group plus dyspepsia, injection site reactions, fatigue and hair loss.
Can I compare the Wegovy and Zepbound percentages directly?
No. They come from different trials with different patients, doses and durations, so the percentages are not a head-to-head comparison. Use them to see what each label reports, not to rank the drugs.
Do these numbers apply to compounded products?
They describe the approved products in the trials. Compounded drugs are not FDA approved and are not reviewed for safety, effectiveness or quality before they are marketed, so the label figures do not describe what a given compounded product will do.
Do side effects go away?
The labels tie dose escalation to tolerability, and both let the prescriber slow the schedule. Whether effects ease for you is something to ask your prescriber, not something a table can promise.
What is the boxed warning?
Both labels carry a boxed warning about thyroid C-cell tumors seen in rodents. It is unknown whether the drugs cause these tumors, including medullary thyroid carcinoma, in humans. Both are contraindicated with a personal or family history of medullary thyroid carcinoma or MEN 2.