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How GLP-1 medicines work: semaglutide, tirzepatide and the newer agents

Updated 3 July 2026 · 7 min read

GLP-1 medicines are the best-evidenced peptides in this library, and the reason the whole category has entered the mainstream. This guide explains what they do in the body and how the newer 'dual' and 'triple' agonists differ. It is educational and does not tell you what to take or at what dose — those are decisions for you and a licensed clinician.

What GLP-1 is

Glucagon-like peptide-1 (GLP-1) is a hormone your gut releases after eating. It nudges the pancreas to release insulin when glucose is high, slows how fast the stomach empties, and signals fullness to the brain. Medicines like semaglutide and liraglutide are engineered to mimic GLP-1 but last far longer than the natural hormone.

Single, dual and triple agonists

  • GLP-1 agonists (semaglutide, liraglutide): act on the GLP-1 receptor alone.
  • GIP/GLP-1 dual agonists (tirzepatide): add the GIP receptor, which appears to improve results for many people.
  • GLP-1/glucagon dual agonists (survodutide, mazdutide): add the glucagon receptor, proposed to raise energy expenditure.
  • Triple agonists (retatrutide): GIP + GLP-1 + glucagon, showing striking phase-2 weight loss but still investigational.

There is also a shift toward convenience: cagrilintide is an amylin analogue studied alongside semaglutide, and orforglipron is an oral small molecule rather than an injected peptide. Approval status differs sharply between these — some are licensed medicines, others are investigational.

Compare the GLP-1 family and their approval status:

How strong is the evidence?

The approved GLP-1 and GIP/GLP-1 agents sit on large phase-3 randomised trials (the STEP, SUSTAIN, SURPASS and SURMOUNT programmes). The newer triple agonists and oral agents have promising data but less long-term follow-up. A high evidence grade means the trials are strong; it does not mean a medicine is right, safe or legal for any given person.

GLP-1 medicines are prescription-only where licensed. Aminove does not restate a personalised schedule or suggest a dose; use these only under a clinician's care.