Beyond the weight-loss headline, how do semaglutide and tirzepatide actually differ?
Updated: 2026-09-09 · GLP-1 and weight
Short answer
Semaglutide acts on one receptor, GLP-1. Tirzepatide acts on two, GIP and GLP-1. That mechanistic difference shows up as somewhat different efficacy and tolerability profiles, and in a direct head-to-head obesity trial tirzepatide produced greater average weight loss. Both share the same family of digestive side effects.
In plain English
- Semaglutide: GLP-1 agonist. Tirzepatide: dual GIP/GLP-1 agonist.
- More receptors does not automatically mean better for everyone; the effect profile shifts too.
- Price, availability and coverage often matter as much as the clinical differences.
- Individual response varies widely; trial averages are not a personal forecast.
What we know
- Tirzepatide's dual GIP/GLP-1 mechanism is well characterised and is the core pharmacological difference.
- A randomised head-to-head obesity trial reported greater average weight loss with tirzepatide.
- Both are approved and both have mainly gastrointestinal adverse effects.
What we don't know yet
- Exactly how much the GIP component contributes in humans is still being studied.
- There is no way to know in advance which one suits a given person better.
Sources
External links to official sources or peer-reviewed studies.