Clinical Data & Patient Experiences
Last Updated: January 16, 2026 | Source: FDA Prescribing Information + Patient Discussion Analysis
The following adverse reactions were reported in placebo-controlled clinical trials and are listed in Wegovy's FDA-approved prescribing information.
| Adverse Reaction | Placebo | 2.4mg |
|---|---|---|
| Nausea | 6% | 44% |
| Diarrhea | 16% | 30% |
| Vomiting | 5% | 24% |
| Constipation | 10% | 24% |
| Abdominal Pain | 6% | 11% |
| Headache | 10% | 14% |
| Fatigue | 3% | 11% |
Source: FDA Prescribing Information for Wegovy (semaglutide), Table 1
Patient-reported experiences and clinical data.
Note: Patient-reported patterns are general guidance — consult your clinician for personal advice.
Clinical: 44% at 2.4mg dose
Nausea typically peaks 2-4 days post-injection, especially during dose increases. The 2.5mg→5mg transition is often the most challenging.
Common triggers: High-fat meals, eating past fullness, large portions
Relief strategies: Ondansetron, ginger, small frequent meals, avoiding trigger foods
Read the full nausea management guideClinical: 6-7%
Unlike nausea, constipation often worsens over time. Reduced food intake (800-1200 cal/day) plus slowed GI motility creates ongoing issues.
Management: Daily MiraLAX, magnesium citrate, fiber supplements, prevention over reaction
Clinical: Listed as "eructation" 3.0-3.3%
FDA data understates this. Sulfur burps — the distinctive rotten-egg-tasting belch — are a common complaint, often accompanied by diarrhoea.
Triggers: Fatty foods, eggs, dairy, overeating
Relief: Pepto-Bismol, Gas-X, avoiding trigger foods, smaller meals
Clinical: Not in trials; added post-marketing
A common pattern: hair thinning typically appears 3-6 months after starting, likely related to rapid weight loss and caloric restriction (telogen effluvium) rather than the medication directly.
Common approaches: Ensure adequate protein (60-80g/day), biotin, multivitamin; usually resolves as weight stabilizes
Clinical: Not prominently reported in trials
Fatigue is common in the first weeks, often related to dramatically reduced caloric intake.
Management: Track calories (minimum 1000-1200), protein shakes, electrolytes, adequate sleep
Medical Disclaimer: This content is for informational purposes only and does not constitute medical advice. Consult your healthcare provider.
Sources: FDA Prescribing Information, patient-reported experiences
