What This Page Explains
This page explains the most common side effects of GLP-1 medications (tirzepatide, semaglutide), why they occur, and how to interpret them.
One-Minute Summary
Most side effects are digestive and temporary. They reflect how the medication affects appetite, stomach emptying, and gut hormones. Common side effects include nausea (24-33% of patients in clinical trials, per SURMOUNT-1, NEJM 2022), digestive changes, and appetite suppression. Most are mild and improve as your body adjusts. Start with low doses, eat smaller meals, and stay hydrated. Seek medical help for severe symptoms.
Most Common Side Effects
- Nausea
- Fullness
- Bloating
- Constipation
- Diarrhoea
- Reflux
- Reduced appetite
These usually appear early and improve over time.
Why Side Effects Happen
GLP-1 medications:
- Slow stomach emptying
- Alter gut hormone signalling
- Change appetite and satiety cues
These effects can temporarily disturb digestion.
What Is Generally Normal
- Mild to moderate nausea
- Appetite loss
- Changes in bowel habits
- Food aversions
- Earlier fullness
What Requires Medical Assessment
- Severe abdominal pain
- Ongoing vomiting
- Inability to keep fluids down
- Signs of dehydration
- Fainting
- Jaundice
Practical Management
Eating Strategies
- Eat slowly
- Choose smaller, more frequent meals
- Avoid greasy or very heavy foods
- Stop when satisfied, not full
- Don't lie down immediately after eating
Hydration
- Prioritise fluids throughout the day
- Sip water regularly
- Herbal teas can help settle the stomach
- Monitor for signs of dehydration
Medication Timing
- Maintain consistent weekly dosing
- Take on the same day each week
- Starting at a low dose and increasing gradually helps minimise side effects
Managing Specific Side Effects
Nausea
- Most common, usually mild
- Often worst in the first 2-4 weeks
- Improves as your body adjusts
- Eat smaller portions and avoid fatty foods
- Stay hydrated
Constipation
- Increase fibre intake gradually
- Drink plenty of water
- Stay physically active
- Consider speaking with your care team if persistent
Diarrhoea
- Stay well hydrated
- Avoid foods that worsen symptoms
- Usually temporary during dose adjustments
- Seek medical advice if severe or lasting more than a few days
When to Seek Medical Help
Seek immediate medical attention for:
- Severe abdominal pain that doesn't go away
- Severe vomiting or diarrhoea
- Signs of allergic reaction (rash, swelling, difficulty breathing)
- Signs of low blood sugar (shakiness, sweating, confusion — especially if diabetic)
- Any symptom that concerns you
Medical Notice
This information is educational and does not replace medical advice. Seek medical care for concerning or severe symptoms.