⚠️ Medical disclaimer: This page is for informational purposes only. If you experience severe or persistent side effects, contact your healthcare provider immediately.
GLP-1 medications are generally well-tolerated, but they do cause side effects — particularly in the first few weeks of treatment and after each dose increase. Here is what you can expect and how to manage the most common issues.
Most Common Side Effects
1. Nausea
Nausea is the most commonly reported side effect — affecting around 40–50% of users at some point. It is usually worst in the first 2–4 weeks and improves as your body adjusts.
How to manage it:
- Eat smaller meals — large portions worsen nausea on GLP-1s
- Avoid fatty, greasy, or spicy foods
- Eat slowly and stop before you feel completely full
- Stay upright for 30–60 minutes after eating
- Ginger tea or ginger chews can help
- Ask your doctor about anti-nausea medication if it is severe
2. Diarrhea
GLP-1 medications slow gastric emptying, which can disrupt normal bowel patterns. Affects around 20–30% of users and typically improves within the first month.
- Stay well hydrated
- Avoid high-fat and high-sugar foods
- Electrolyte supplements can help replace what you lose
3. Constipation
Around 20–25% of users experience constipation — the opposite of diarrhea but equally common.
- Increase fibre intake — vegetables, legumes, whole grains
- Drink at least 2 litres of water daily
- Light walking helps stimulate the gut
- Fibre supplements can help
4. Vomiting
Affects around 10–20% of users, usually in the first weeks. If persistent or severe, contact your doctor — you may need to stay on a lower dose longer before increasing.
5. Fatigue
Some users feel tired, particularly early on. This is partly from eating less (lower calorie intake) and partly the body adjusting. Ensure you are meeting your protein and electrolyte needs.
Less Common Side Effects
Hair Loss (Telogen Effluvium)
Hair thinning or shedding typically starts 3–6 months into treatment. This is caused by rapid weight loss and calorie reduction — not the medication directly. It is usually temporary.
- Maintain adequate protein intake (1.2–1.6g per kg of body weight daily)
- Take a multivitamin covering iron, zinc, and biotin
- Hair typically regrows within 6–12 months
Muscle Loss
Rapid weight loss can include loss of lean muscle, not just fat. Actively managing this is important.
- Prioritise protein in every meal (at least 25–30g per meal)
- Incorporate resistance training
- Consider a protein supplement if you struggle to meet targets
Ozempic Face / Ozempic Butt
These informal terms describe facial and buttock fat loss during rapid weight loss. This is a consequence of losing significant body fat quickly, not a direct drug side effect. Slower, steady dose titration can help.
Serious Side Effects (Rare — Seek Medical Attention)
- Pancreatitis — severe abdominal pain radiating to the back
- Gallbladder problems — pain in the upper right abdomen
- Kidney issues — decreased urination, swelling
- Severe allergic reaction — difficulty breathing, facial swelling
- Thyroid concerns — GLP-1s carry an advisory about thyroid C-cell tumours (noted in animal studies)
⚠️ Seek emergency medical care immediately if you experience severe abdominal pain, difficulty breathing, or signs of an allergic reaction.
Side Effects by Medication
Ozempic / Wegovy (semaglutide) — Nausea: High | Diarrhea: Moderate | Overall: Moderate
Mounjaro / Zepbound (tirzepatide) — Nausea: High | Diarrhea: High | Overall: Stronger than semaglutide
Saxenda (liraglutide) — Nausea: Moderate | Diarrhea: Moderate | Overall: Milder overall
Note: Tirzepatide tends to cause more diarrhea than semaglutide but produces stronger weight loss results. Many users find the trade-off worthwhile.
→ See our Supplements Guide for the best supplements to manage GLP-1 side effects.