GLP-1 receptor agonists including semaglutide (Ozempic, Wegovy, Rybelsus) and tirzepatide (Mounjaro) are increasingly used for type 2 diabetes and obesity. This guide outlines practical strategies for managing their adverse effects based on latest clinical evidence.
1. Gastrointestinal Side Effects
Nausea, vomiting, diarrhoea, constipation, abdominal pain, and bloating are the most common adverse effects. They occur most frequently during dose escalation and tend to fade over time. Practical tips: eat slowly, choose smaller portions, avoid late-night eating, follow a low-fat diet, and drink at least 2-2.5 litres of water daily.
2. Acute Pancreatitis Risk
Rarely but seriously, GLP-1 agonists can cause acute pancreatitis. Warning signs: severe abdominal pain radiating to the back, nausea and vomiting. If suspected, the medication must be stopped immediately.
3. Hair Loss (Telogen Effluvium)
Up to 1 in 10 patients experience temporary hair loss due to rapid weight loss (telogen effluvium). It appears 3-4 months after starting treatment and resolves within 3-6 months.
4. NAION Vision Risk
A UK regulatory warning flagged increased NAION risk with all semaglutide forms. NAION causes sudden painless vision loss. If this occurs, semaglutide must be stopped immediately and an ophthalmologist consulted urgently.
5. Drug Interactions
GLP-1 agonists slow gastric emptying, potentially affecting absorption of narrow-therapeutic-index medications (digoxin, lithium, warfarin). For women on oral HRT, transdermal oestrogen and a levonorgestrel-releasing IUD are recommended.
GLP-1 Drugs vs Bariatric Surgery
GLP-1 agonists are valuable for mild-to-moderate obesity (BMI 27-35). For severe obesity (BMI 40+), gastric bypass or sleeve gastrectomy offer far more durable results, including 70-80% type 2 diabetes remission rates.
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How long do GLP-1 side effects last?
GI side effects fade over time. Hair loss appears at 3-4 months and resolves by 3-6 months. Serious effects (pancreatitis, NAION) require immediate discontinuation.
Can GLP-1 drugs replace bariatric surgery?
For mild-to-moderate obesity they may help, but for severe obesity and serious comorbidities, bariatric surgery delivers far more durable results. Weight regain on cessation is also an important consideration.
Source: Kevin Fernando, MBChB. Medscape Family Medicine, 18 March 2026. MHRA Safety Updates 2024-2025.