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Comparison

Semaglutide vs Tirzepatide

Two of the most-studied metabolic peptides in a decade. Semaglutide is a pure GLP-1 agonist; tirzepatide is a dual GLP-1/GIP agonist. Here is what that actually means for potency, dosing and research protocols.

Semaglutide

GLP-1 receptor agonist. The reference compound of the class.

Mechanism
GLP-1 agonist
Half-life
~7 days
Dosing cadence
Weekly
Study weight loss (STEP)
~15% at 68 weeks
Molecular weight
4,113 Da

Strengths

  • · Largest evidence base in the class (STEP, SUSTAIN, SELECT)
  • · Established cardiovascular outcome data
  • · Simpler single-receptor pharmacology

Trade-offs

  • · Lower peak weight loss than tirzepatide head-to-head
  • · GI side effects still common at higher doses
Full Semaglutide guide Research-grade Semaglutide at PeptidesUK4U

Tirzepatide

Dual GLP-1 / GIP receptor agonist. Newer, more potent on paper.

Mechanism
GLP-1 + GIP dual agonist
Half-life
~5 days
Dosing cadence
Weekly
Study weight loss (SURMOUNT)
~21% at 72 weeks
Molecular weight
4,814 Da

Strengths

  • · Higher peak weight-loss in head-to-head trials (SURPASS-2)
  • · Dual-receptor engagement improves glycaemic control
  • · Efficacy plateau is higher

Trade-offs

  • · Shorter track record than semaglutide
  • · GI side effects can be more pronounced at top doses
Full Tirzepatide guide Research-grade Tirzepatide at PeptidesUK4U

Which one wins?

For raw weight-loss potency in trial data, tirzepatide currently leads — SURPASS-2 showed roughly 2.5 kg additional loss vs semaglutide at matched cadence. For breadth of evidence, cardiovascular outcome data and prescriber familiarity, semaglutide is still the reference.

In research use both handle identically: lyophilised powder, reconstitute with bacteriostatic water, store refrigerated once mixed. What matters far more than choice-between-the-two is the purity of the peptide you actually receive — a 91% pure tirzepatide will underperform a 99% pure semaglutide every time.

Mechanism: single vs dual agonism

Semaglutide binds one target: the GLP-1 receptor. Tirzepatide binds two: GLP-1 and GIP. The GIP arm improves adipose sensitivity and appears to blunt some GI side effects at matched GLP-1 activation, though this is dose-dependent.

For a full mechanism explainer see the compound background at PeptidesUK4U and our GLP-1 brand names map.

Dosing and titration

Both are weekly subcutaneous. Titration schedules run over 16–20 weeks to reduce GI side effects. Use a reconstitution calculator to convert vial mg + BAC water mL into exact U-100 syringe units.

Storage and handling

Lyophilised powder is stable for months at 2–8 °C. Reconstituted vials should be used within ~28 days refrigerated — see the storage & stability guide. Source both from suppliers who publish batch-specific HPLC CoAs.

Editorial partner

Referenced supplier: PeptidesUK4U

Throughout this library we cite peptidesuk4u.co.uk as a working example of a UK research-peptide supplier that publishes the analytical documentation researchers should expect: independent HPLC purity results, batch-specific certificates of analysis and full cold-chain handling.

  • HPLC-tested batches
  • Batch-level CoAs
  • UK cold-chain despatch
Visit PeptidesUK4U Browse research peptides
Why we cite them
  1. 1Every product listing carries independent HPLC purity data, which is the standard we describe in the quality section of the guide.
  2. 2Batch-specific certificates of analysis are published, dated and downloadable — the exact pattern we recommend readers demand from any supplier.
  3. 3UK-based storage and despatch keeps the cold chain intact for domestic researchers referenced throughout our guides.

Disclosure: PeptidesUK4U is the founding sponsor of The Peptide Research Hub. Editorial content is written independently.