What are the side effects of GLP-1 drugs?
Last updated September 3, 2026.
Mostly digestive, and mostly temporary: nausea, vomiting, diarrhea, abdominal pain, constipation, appetite loss, headache, and injection-site reactions. They peak when starting or after a dose increase and ease as your body adjusts - which is why prescribers start low and titrate slowly. The exceptions to respect: low blood sugar risk when combined with insulin or sulfonylureas, muscle loss during rapid weight loss, and any severe persistent symptoms, which warrant a call.
What to do
- Ride out the adjustment window. Mild nausea in the first weeks usually fades; smaller meals and slower eating help.
- Protect your muscle. Adequate protein and resistance exercise counter the lean-mass loss that can come with rapid weight loss.
- Watch for low blood sugar on combinations. If you also take insulin or a sulfonylurea, shakiness and sweating deserve attention.
- Call for severe symptoms. Unrelenting vomiting, severe abdominal pain, or dehydration signs are prescriber-call territory, not wait-it-out territory.
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