Tirzepatide
Dual GIP + GLP-1 agonist — two incretin arms from one molecule.
Metabolic · 8 min read · updated 13 Aug 2026
Research use only. The ranges below are what published studies and community protocols report. They are reference material for laboratory research, not medical advice or a recommendation for human or veterinary use.
The compound
Tirzepatide
View- Type
- GIP/GLP-1 Receptor Agonist
- CAS
- 2023788-19-2
- Formula
- C₂₂₅H₃₄₈N₄₈O₆₈
- Mass
- ~4813.45 Da
At a glance
- Class
- Dual GIP / GLP-1 receptor agonist
- Length
- 39 amino acids
- Molecular weight
- ~4813.45 Da
- CAS
- 2023788-19-2
- Half-life
- ~5 days
- Cadence studied
- Once weekly
- Vial sizes stocked
- 10 mg, 30 mg, 60 mg
Tirzepatide is built on the GIP peptide backbone rather than the GLP-1 backbone, then engineered to hit both receptors. Two Aib substitutions (positions 2 and 13) confer DPP-4 resistance, and a C20 fatty diacid attached at Lys20 provides the albumin binding that stretches the half-life to roughly five days.
Its receptor profile is deliberately unbalanced: tirzepatide is a full agonist at the GIP receptor and a partial, biased agonist at the GLP-1 receptor. The GLP-1 arm is tuned to favour cAMP generation over β-arrestin recruitment, which reduces receptor internalisation and desensitisation. In practical terms it delivers strong GLP-1-like signalling with less receptor down-regulation than a balanced full agonist would produce at the same occupancy.
Glucose-dependent insulinotropic polypeptide (GIP) is the second incretin, and for years it was written off as therapeutically useless because GIP responsiveness is blunted in hyperglycaemia. Tirzepatide is the compound that revived interest in it: sustained co-agonism appears to restore GIP sensitivity, and GIP receptor signalling in adipose tissue and in the central nervous system contributes to both the metabolic and the anti-nausea profile.
Why two receptors behave differently from one
- Adipose tissue: GIP receptors are densely expressed on adipocytes, where signalling improves lipid buffering and post-prandial triglyceride clearance. GLP-1 receptors are essentially absent there. This is the clearest tissue-level divergence between the two arms.
- Central nervous system: GIP receptor agonism in the hindbrain appears to blunt the nausea signal generated by GLP-1 receptor activation. This is the leading explanation for why tirzepatide tolerates a higher effective incretin load than a pure GLP-1 agonist.
- β-cell: both receptors amplify glucose-stimulated insulin secretion through Gs/cAMP, and the effects are additive rather than redundant.
- Gastric emptying: the delay is driven mainly by the GLP-1 arm, and like semaglutide it partially adapts over the first few months of exposure.
What the research literature covers
- SURPASS-1 through SURPASS-5 — glycaemic endpoints across monotherapy and combination settings at 5, 10 and 15 mg weekly.
- SURPASS-2 — the head-to-head against semaglutide 1 mg, the study most often cited when comparing the two molecules.
- SURMOUNT-1 and SURMOUNT-2 — body-weight endpoints in subjects without and with type 2 diabetes.
- Mechanistic work isolating the GIP contribution using receptor antagonists and knockout models.
Reading the dose ladder
The published schedule uses six steps of 2.5 mg each, held for four weeks apiece. The first step is explicitly a tolerance step, not a treatment dose — the trials treat 5 mg as the lowest maintenance level. Above 10 mg the incremental benefit narrows while the tolerability burden keeps rising, which is why a substantial share of trial subjects held at 10 mg rather than pushing to 15 mg.
The 60 mg vial stocked here is a bulk format. It is convenient for long protocols but it commits you to a single reconstitution concentration for a long stretch, so choose the fill volume with the maintenance dose in mind rather than the starting dose.
Storage
- Lyophilised: 2–8 °C, or −20 °C for extended storage. Protect from light.
- Reconstituted: 2–8 °C and used within about 28–30 days. Never freeze.
- A 60 mg vial at 20 mg/ml lasts a long time at maintenance doses — track the reconstitution date on the vial, because the 30-day window will expire before the volume runs out.
Cautions
- Gastrointestinal effects mirror the GLP-1 class and are strongest in the first week after each step up.
- Because two incretin arms are engaged, co-administration with any other incretin agonist in the same model compounds exposure rather than adding a distinct mechanism.
- The same class-level signals apply as for semaglutide: rodent thyroid C-cell findings, gallbladder events, and pancreatitis at low frequency.
- Injection-site reactions are reported more often than with semaglutide, likely reflecting the larger injected volume at higher doses.
References & credit
- 1Frías JP et al., NEJM 2021 — SURPASS-2 — tirzepatide versus semaglutide 1 mg.
- 2Jastreboff AM et al., NEJM 2022 — SURMOUNT-1 — body-weight endpoints.
- 3Coskun T et al., Mol Metab 2018 — Preclinical characterisation of the dual GIP/GLP-1 agonist.
- 4Willard FS et al., JCI Insight 2020 — Biased agonism at the GLP-1 receptor — the reduced β-arrestin recruitment described above.
This article was written in-house. Where a dose range reflects community practice rather than a published trial, the community references we consulted are credited above and the article says which is which.