Why Do GLP-1 Medications Cause Side Effects?
GLP-1 and GIP receptor agonists work by mimicking natural gut hormones that signal satiety to the brain and slow down gastric emptying (the rate at which food moves from the stomach into the intestine). Because digestion slows down, the stomach stays fuller for longer, which can trigger nausea, indigestion, or reflux during initial dose escalation.
Top 4 Side Effects and Practical Relief Strategies
Nausea (Most Common in Weeks 1–4)
Nausea is the most frequently reported side effect when initiating treatment or increasing dosage. It is usually temporary and resolves within 3 to 7 days of a dose increase.
Clinical Recommendations:
• Stop eating the moment you feel 70% full; overeating is the #1 trigger of severe nausea.
• Sip cold, clear drinks or peppermint/ginger tea throughout the day.
• Avoid greasy, heavily spiced, or ultra-processed meals.
• Do not lie down flat immediately after finishing a meal.
Constipation & Slow Motility
Because digestive transit is slowed, stools can dry out if your fluid intake is inadequate.
Clinical Recommendations:
• Aim for 2.0 to 2.5 litres of water daily.
• Include gentle soluble fibre (oats, chia seeds, chia puddings, psyllium husk).
• Consult your pharmacist regarding gentle osmotic laxatives (e.g. Macrogol) if symptoms persist past 3 days.
Fatigue & Low Energy
Many patients eat substantially fewer calories in the initial weeks. A sharp drop in caloric intake and carbohydrates naturally causes transient sluggishness.
Clinical Recommendations:
• Ensure adequate protein intake (aim for 60g to 90g daily) to protect lean muscle mass.
• Consider electrolyte replacement drinks if you are eating significantly smaller portions.
Heartburn & Acid Reflux
Delayed stomach emptying increases the risk of stomach acid splashing back into the esophagus, especially in the evening.
Clinical Recommendations:
• Finish your final meal at least 3 hours before going to bed.
• Limit acidic foods (tomatoes, citrus fruits, carbonated drinks).
• Over-the-counter antacids (e.g., Gaviscon) can provide fast symptomatic relief.
Have Questions About Medication Dosing?
Prescribers at Click Pharmacy provide ongoing clinical support, dosing guidance, and monitoring throughout your weight loss journey.
When to Seek Immediate Medical Attention
While mild gastrointestinal effects are normal, contact your GP, call NHS 111, or attend A&E immediately if you experience severe, persistent abdominal pain radiating to your back (a potential symptom of acute pancreatitis), persistent inability to keep liquids down, or signs of an allergic reaction.