Semaglutide vs TirzepatideSemaglutide vs tirzepatide — the molecule-level comparison: single vs dual incretin agonism, SURPASS head-to-head data, weight and glucose outcomes.

Short answer: Semaglutide is a GLP-1 agonist; tirzepatide adds GIP agonism (dual incretin). The SURPASS-2 head-to-head trial showed tirzepatide superior on both HbA1c and weight at matched comparison. Tirzepatide is sold as Mounjaro (diabetes) and Zepbound (obesity).

The mechanism difference

Semaglutide hits one incretin receptor (GLP-1). Tirzepatide hits two (GIP + GLP-1) — dual agonism produces greater metabolic effect in trials. Both are weekly injections with similar GI side-effect profiles.

Trial numbers

SURPASS-2 (head-to-head): tirzepatide superior on HbA1c and weight at every dose level
Weight loss: ~15% semaglutide vs ~20% tirzepatide (obesity doses)
GI side effects: similar profiles, both dose-escalation related

Ozempic (semaglutide) FDA Prescribing Information, Novo Nordisk, 2024.

STEP 1 Trial — Once-Weekly Semaglutide in Adults with Overweight or Obesity (Wilding et al., NEJM 2021).

SUSTAIN 6 — Semaglutide and Cardiovascular Outcomes in Type 2 Diabetes (Marso et al., NEJM 2016).

American Diabetes Association — Standards of Care in Diabetes — 2026.

NICE Guideline NG28 — Type 2 diabetes in adults: management.

World Health Organization — Diabetes fact sheet.

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