Semaglutide: Side Effects & Safety

Semaglutide has been extensively studied in clinical trials involving over 16,000 participants. The most common side effects are gastrointestinal and are typically mild to moderate, decreasing in frequency and severity with continued use. Serious adverse events are rare but include pancreatitis and potential thyroid risks.

• Nausea (20–44%): Most common, usually improves with dose escalation
• Diarrhea (8–30%)
• Vomiting (5–24%)
• Constipation (5–24%)
• Abdominal pain (5–20%)
• Headache (10–14%)
• Injection site reactions: Mild and transient
• Fatigue and dizziness: Less common

• Pancreatitis: Acute pancreatitis has been reported — discontinue if suspected. Monitor for severe abdominal pain
• Thyroid C-cell tumors: Boxed warning based on rodent data showing thyroid medullary carcinoma. Not confirmed in humans but contraindicated with personal/family history of MTC or MEN2
• Gallbladder events: Increased incidence of cholelithiasis and cholecystitis, likely related to rapid weight loss
• Diabetic retinopathy: Rapid glucose improvement can temporarily worsen diabetic retinopathy in patients with pre-existing disease
• Suicidal ideation: Post-marketing reports under investigation by FDA; causal relationship not established

• Personal or family history of medullary thyroid carcinoma (MTC)
• Multiple Endocrine Neoplasia syndrome type 2 (MEN2)
• Known hypersensitivity to semaglutide
• Pregnancy and breastfeeding (discontinue at least 2 months before planned pregnancy)
• History of pancreatitis (use with caution)

See the semaglutide overview for complete information.