Is constipation a known side effect of GLP-1 receptor agonists, or is diarrhea more common?

GLP-1 Receptor Agonists: Diarrhea is More Common Than Constipation, But Both Occur

Diarrhea is more frequently reported than constipation with GLP-1 receptor agonists, though both are recognized side effects. The most common gastrointestinal adverse effects are nausea (occurring in approximately 25% of patients), followed by diarrhea (up to 10-13% of patients), with constipation being less frequent but still significant (approximately 7-8% of patients) 1.

Relative Frequency of GI Side Effects

The 2025 guideline evidence clearly establishes the hierarchy of gastrointestinal adverse effects:

• Nausea: Most common (21-25% incidence)
• Diarrhea: Second most common (10-13% incidence)
• Vomiting: 9-10% incidence
• Constipation: Less common (7-8% incidence) 1, 2

Recent meta-analyses confirm this pattern, with all six major GI adverse events showing statistically significant increased risk compared to placebo (p < 0.00001): nausea (RR: 2.90), diarrhea (RR: 1.97), and constipation (RR: 2.41) 3.

Drug-Specific Differences

Important variation exists between specific GLP-1 receptor agonists:

• Semaglutide carries the highest risk for constipation and demonstrates significantly higher diarrhea risk compared to other agents 3, 4, 5
• Tirzepatide (dual GIP/GLP-1 agonist) shows the highest risk ratios for both nausea and diarrhea 3, 5
• Dulaglutide and liraglutide have higher rates of both diarrhea and constipation compared to semaglutide and exenatide 6
• Exenatide appears to have a relatively safer GI profile overall 6

Clinical Management Approach

These side effects are dose-dependent and worsen with escalation 1, 2. The 2024 Anaesthesia guideline provides specific management strategies:

For Diarrhea:

• Reduce meal size
• Limit alcohol and carbonated drinks
• Slow dose titration 2

For Constipation:

• Avoid high-fat diet
• Increase dietary fiber
• Ensure adequate hydration 1, 2

General Mitigation:

• Start at low doses and titrate slowly
• Eat smaller meals
• Stop eating when feeling full
• Avoid high-fat or spicy foods
• Drink plenty of water 1

Important Caveats

Many patients develop tolerance over time, and some experience no side effects with dose escalation 1. However, GI adverse events are typically mild and lead to discontinuation in fewer than 5% of patients 7. The side effects are generally self-limiting and reversible upon drug cessation 8.

Both diarrhea and constipation can occur in the same patient at different times during treatment, reflecting the complex effects of GLP-1 receptor agonists on gastric emptying and intestinal motility 2.

When counseling patients, emphasize that while diarrhea is more common overall, constipation is also a recognized side effect that requires monitoring and management, particularly with semaglutide 3, 4, 5.