Wegovy Side Effects: Onset, Duration
What to expect from Wegovy injections - when side effects typically begin, how long they last, and NHS-recommended strategies to manage common reactions.
Key Takeaways
- Most common: Nausea (44%), diarrhoea (30%), vomiting (24%) - usually mild-moderate
- When they start: Gastrointestinal effects often begin within 24-72 hours of first 0.25mg dose
- Peak timing: Side effects worst during dose escalation (weeks 5-12 at 0.5-1.7mg doses)
- Duration: 75% resolve within 2-8 weeks as body adjusts
- Serious risks: Pancreatitis (0.4%), gallstones (1.6%), suicidal thoughts (monitor mood)
Complete guide to Wegovy injection side effects: when they start, how long they last, and NHS-recommended management strategies for nausea, diarrhoea and other common reactions.
Most Common Wegovy Side Effects
Based on UK Yellow Card reports and STEP clinical trials:
1. Gastrointestinal (Very Common: >1 in 10)
- Nausea: 44% of users (peaks at 1.0-1.7mg doses)
- Diarrhoea: 30% (often fatty stools from delayed gastric emptying)
- Vomiting: 24% (typically during first 8 weeks)
- Constipation: 20%
- Abdominal pain: 18%
2. General (Common: >1 in 100)
- Fatigue: 15% (usually improves after week 12)
- Headache: 13% (often dehydration-related)
- Dizziness: 9% (common when standing quickly)
- Injection site reactions: 8% (redness, itching - rotate sites)
3. Metabolic (Common)
- Hypoglycaemia: 6% (mainly in diabetics on insulin/sulfonylureas)
- Increased pancreatic enzymes: 4% (monitor for pancreatitis)
NHS Advice: Most common side effects are dose-dependent and improve with continued use. Slower dose escalation may help sensitive patients.
When Wegovy Side Effects Start
Wegovy side effect onset timeline
| Time After Starting | Most Likely Side Effects | Typical Severity |
|---|---|---|
| 24-72 hours | Mild nausea, fatigue | Mild (2-3/10) |
| 1-2 weeks | Diarrhoea/constipation, headache | Moderate (4-6/10) |
| Weeks 5-12 | Peak GI effects at 1.0-1.7mg doses | Moderate-severe (5-7/10) |
| Week 13+ | Gradual improvement at 2.4mg maintenance | Mild (1-3/10) |
How Long Wegovy Side Effects Last
| Side Effect | Typical Duration | When to Seek Help |
|---|---|---|
| Nausea | 2-6 weeks (90% resolve by week 12) | If preventing eating/drinking >24hrs |
| Diarrhoea | 3-10 days (usually <1 week) | Blood in stool or >3 days without improvement |
| Constipation | May persist intermittently | No bowel movement >4 days |
| Fatigue | 2-4 weeks | If accompanied by dizziness/confusion |
| Injection site reactions | 1-3 days per incident | Signs of infection (pus, spreading redness) |
Pattern: Most side effects follow a "hump-shaped" curve - increasing during dose escalation (weeks 1-12), then decreasing at maintenance dose (2.4mg).
Serious Side Effects Requiring Immediate Medical Attention
Stop Wegovy and seek urgent care if you experience:
- Pancreatitis: Severe persistent abdominal pain radiating to back with vomiting
- Gallbladder problems: Right upper quadrant pain, fever, jaundice
- Suicidal thoughts: New or worsening depression/ideation
- Severe allergic reactions: Swelling of face/throat, difficulty breathing
- Diabetic retinopathy changes: Sudden vision changes in diabetics
UK Incidence Rates:
- Acute pancreatitis: 0.4% (4 in 1,000 users)
- Cholelithiasis (gallstones): 1.6%
- Major depressive disorder: 0.9%
- Anaphylaxis: 0.2%
NHS-Recommended Management Strategies
For Nausea
- Inject at bedtime to sleep through worst effects
- Eat smaller, bland meals (BRAT diet: bananas, rice, applesauce, toast)
- Ginger supplements or acupressure bands
- Ask GP about antiemetics if severe (e.g. cyclizine)
For Diarrhoea
- Reduce dietary fat to ≤30% of calories
- Stay hydrated with oral rehydration solutions
- Loperamide may be used short-term (consult pharmacist)
For Constipation
- Increase soluble fibre (oats, psyllium)
- Maintain adequate hydration (2-3L water daily)
- Consider lactulose or macrogol if needed
Dose Adjustment Tip: If side effects are intolerable at 1.0mg, your GP may recommend maintaining at 0.5mg for an extra 4 weeks before escalating.
Frequently Asked Questions
Why am I nauseous only after certain doses?
Nausea peaks at 1.0-1.7mg as your body adapts to higher GLP-1 levels. Many find the 2.4mg maintenance dose less nauseating than mid-range doses.
Can I take anti-sickness tablets with Wegovy?
Yes, GPs may prescribe cyclizine or ondansetron short-term. Avoid prochlorperazine (may worsen constipation). Always consult your doctor first.
Do side effects mean Wegovy is working?
Not necessarily. While GI effects correlate with drug exposure, their absence doesn't indicate treatment failure. Weight loss can occur without side effects.
Why are my side effects worse than my friend's?
Individual sensitivity varies based on genetics, BMI, diet, and medication history. Women often report more nausea than men due to hormonal interactions.
Should I stop Wegovy if side effects are bad?
Never stop abruptly without medical advice. Your GP may recommend: (1) Slower dose escalation (2) Temporary dose reduction (3) Switching to alternative if persistent.
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Medical Content Manager
Nabeel is a co-founder and medical content manager of Chemist Doctor. He works closely with our medical team to ensure the information is accurate and up-to-date.
Medical Doctor
Dr. Talal is a GMC registered doctor and medical reviewer at Chemist Doctor. He ensures clinical accuracy and reliability across health content.
Medical Director
Usman is a co-founder and medical director of Chemist Doctor. He leads the organisation's strategic vision, bridging clinical and operational priorities.
Review Date: 18 November 2025
Next Review: 20 May 2026
Published on: 18 November 2025
Last Updated: 19 November 2025
