The most common Wegovy side effects are gastrointestinal. In the trials, nausea affected 44% of people on Wegovy against 16% on placebo, and diarrhea 30% against 16%. The gap between the two columns is the part the drug is responsible for. Serious but uncommon risks include pancreatitis and gallbladder disease, and the label carries a boxed warning for thyroid C-cell tumors.
Side-effect probability vs placebo
Percent of Wegovy trial participants reporting each side effect at any time during the trial, vs the placebo arm.
Primary sources: Wegovy FDA label, Table 3 (2.4 mg vs placebo) · FDA prescribing information (DailyMed)
- Nausea44% vs 16%
- Diarrhea30% vs 16%
- Vomiting24% vs 6%
- Constipation24% vs 11%
- Abdominal pain20% vs 10%
- Headache14% vs 10%
- Fatigue11% vs 5%
Individual experience varies. Most GI side effects resolve over weeks 4–12 as the body adjusts.
Detailed safety information
Important safety information for Wegovy
Summarized from the FDA-approved prescribing information. Always review the full label and discuss with your prescriber.
FDA Boxed Warning
Risk factors:Personal/family history of medullary thyroid cancerMultiple Endocrine Neoplasia type 2Pancreatitis historyType 1 diabetes
Risk of thyroid C-cell tumors. Contraindicated in patients with personal or family history of MTC or MEN 2.
Contraindications (3)
Risk factors:Hypersensitivity to active ingredientPregnancyPersonal/family MTC historyMEN 2 syndrome
- Personal or family history of medullary thyroid carcinoma
- Multiple Endocrine Neoplasia syndrome type 2
- Known serious hypersensitivity to semaglutide
Common side effects
- Nausea (most common)
- Diarrhea
- Vomiting
- Constipation
- Abdominal pain
- Headache
Serious side effects (6)
Risk factors:Pancreatitis historyGallbladder diseaseKidney impairmentDiabetic retinopathyConcurrent insulin / sulfonylurea
- Pancreatitis
- Gallbladder disease
- Acute kidney injury
- Hypersensitivity / anaphylaxis
- Hypoglycemia (with insulin or sulfonylureas)
- Diabetic retinopathy complications
Information is educational and not a substitute for the full prescribing label or clinical judgment. Read our full medical disclaimer.
Wegovy side effects vs placebo, from the trials
Rates from the Wegovy FDA label, Table 3 (2.4 mg vs placebo). People on placebo reported several of these too, so the difference between the columns is the part attributable to the drug.
| Side effect | On Wegovy | On placebo | Difference |
|---|---|---|---|
| Nausea | 44% | 16% | +28 pts |
| Diarrhea | 30% | 16% | +14 pts |
| Vomiting | 24% | 6% | +18 pts |
| Constipation | 24% | 11% | +13 pts |
| Abdominal pain | 20% | 10% | +10 pts |
| Headache | 14% | 10% | +4 pts |
| Fatigue | 11% | 5% | +6 pts |
Percentages are trial-population rates, not a prediction for any one person. Rates differ by dose and by how fast the dose was raised. Check the Medication Guide dispensed with your own prescription, and tell your prescriber about anything that does not settle.
Managing the common ones
Nausea affected 44% of people on Wegovy in the trials, against 16% on placebo. Stomach side effects are usually worst early in treatment and ease over the following weeks for most people. Smaller, lower-fat meals, stopping at the first sign of fullness and steady fluids help; vomiting or diarrhea that does not settle can dehydrate you enough to injure the kidneys, so tell your prescriber. The GLP-1 side effects guide covers each symptom in more depth.
Serious side effects — when to get care now
- Severe stomach pain that does not go away, sometimes spreading to the back — possible pancreatitis. Stop Wegovy and get care.
- Pain in the upper right abdomen, fever, or yellowing skin or eyes — possible gallbladder disease.
- Vomiting or diarrhea you cannot keep up with, or passing little urine — dehydration can injure the kidneys.
- Swelling of the face, lips or throat, hives, or trouble breathing — a severe allergic reaction.
- A lump or swelling in the neck, trouble swallowing, or lasting hoarseness — symptoms the boxed thyroid warning asks you to report.
- Shakiness, sweating, confusion or a racing heartbeat if you also take insulin or a sulfonylurea — low blood sugar.
FAQ about Wegovy side effects
When do Wegovy side effects start?
Stomach side effects are most common when treatment starts and after each dose increase, and for most people they lessen over the following weeks. Tell your prescriber if they persist or get worse.
Does Wegovy have a boxed warning?
Yes, for thyroid C-cell tumors. The medicine caused them in rodent studies, and it is not known whether it does in people. Wegovy must not be used by anyone with a personal or family history of medullary thyroid carcinoma or with multiple endocrine neoplasia syndrome type 2.
If I stop Wegovy, do I restart at a lower dose?
The label says that after 2 or more missed doses in a row, the dose escalation starts again at a lower dose, to limit stomach side effects.
Editorial summary based on FDA prescribing information. Not a substitute for the full label or your prescriber's judgment. Full medical disclaimer.