Side-by-side · Research reference

GLP-1 (7-37)vsTirzepatide

Side-by-side comparison across mechanism, dosage, evidence, side effects, administration, and stack synergies. Citations on every claim where available.

AHuman-MechanisticHUMAN-REVIEWED16/43 cited

BFDA-ApprovedFlagship14/45 cited

GLP-1 (7-37)

Incretin Hormone · Native Peptide

~2 minHalf-lifeAlavi 2021 Ding 2017

3297.7 DaMolecular weightAlavi 2021

1922Discovery year

Research use only · IV/SC in experimental settings

Tirzepatide

GIP+GLP-1 Dual Agonist · FDA-Approved

2.5–15 mgWeekly doseZEPBOUND (tirzepatide) injecti 2023

20.9%Body-weight ↓Jastreboff 2022

~5 daysHalf-lifeZEPBOUND (tirzepatide) injecti 2023

SQ · Abdomen / thigh / arm · Once weekly

01Mechanism of Action

Parameter

GLP-1 (7-37)

Tirzepatide

Primary target

GLP-1 receptor (class B GPCR)Koole 2015

GIP receptor (GIPR) + GLP-1 receptor (GLP-1R)Frias 2018

Pathway

GLP-1R activation → cAMP production → PKA signaling → insulin secretion (pancreatic β-cells)Lu 2025 Koole 2015

Dual GIPR/GLP-1R agonism → ↑insulin (glucose-dependent), ↓glucagon, ↓gastric emptying, ↓appetite, ↑energy expenditure (via GIP component)Jastreboff 2022 Frias 2018

Downstream effect

Glucose-dependent insulin release, glucagon suppression, delayed gastric emptying, reduced food intakeLu 2025 Ding 2017

Profound glycemic improvement and weight reduction; cardiometabolic benefitsJastreboff 2022

Feedback intact?

Yes — physiological secretion and degradation preserved

Glucose-dependent insulin release preserves physiological feedback

Origin

Endogenous peptide cleaved from proglucagon in intestinal L cells; secreted postprandially

39-AA peptide with C-20 fatty-acid acylation. Single molecule with balanced GIP + GLP-1 affinityFrias 2018

Antibody development

—

02Dosage Protocols

Parameter

GLP-1 (7-37)

Tirzepatide

Clinical use

None — native GLP-1 not used therapeutically

Engineered analogues (semaglutide, liraglutide) used clinically.Friedman 2024

—

Research dosing

Variable — 0.1–10 nmol/kg in animal models

Used as reference standard for analogue comparison.

—

Half-life

~2 minutes (plasma)Alavi 2021 Ding 2017

Requires continuous infusion for sustained effect.

~5 days (116 h)ZEPBOUND (tirzepatide) injecti 2023

Modified analogues

t½ extended to 13 h (liraglutide), 165 h (semaglutide)

Via DPP-4 resistance + fatty acid acylation.

—

Standard dose (T2D)

—

5–15 mg / weekZEPBOUND (tirzepatide) injecti 2023

Standard dose (weight)

—

5, 10, or 15 mg / week (titrated)ZEPBOUND (tirzepatide) injecti 2023 Jastreboff 2022

Titration schedule

—

2.5 mg → +2.5 mg every 4 weeks → 15 mg max

Slower titration mitigates GI side effects.

Evidence basis

—

FDA-approved · Phase 3 RCTs (SURMOUNT, SURPASS)Jastreboff 2022 ZEPBOUND (tirzepatide) injecti 2023

Duration

—

Indefinite for chronic indication

Reconstitution

—

Pre-filled commercial pen. Research vial: bacteriostatic water per label.

Timing

—

Once weekly, any time of day

03Metabolic / Fat Loss Evidence

Parameter

GLP-1 (7-37)

Tirzepatide

Mechanism

GLP-1R activation in hypothalamic satiety centers (arcuate nucleus) reduces food intakeLu 2025

Effect demonstrated with long-acting analogues (liraglutide).Lu 2025

—

Native GLP-1 efficacy

Minimal — rapid degradation prevents sustained appetite suppression

—

Gastric emptying

Delayed in animal models, contributing to satiety

—

Body weight impact

Not observed with native GLP-1 — requires analogue formulations

—

04Side Effects & Safety

Parameter

GLP-1 (7-37)

Tirzepatide

Native GLP-1

Well-tolerated in research settings; no prolonged exposure data

—

Hypoglycemia risk

Low — insulin secretion is glucose-dependent

—

Analogue side effects

Nausea, vomiting, diarrhea (GLP-1R agonists)

Not applicable to native GLP-1 due to non-therapeutic use.

—

GLP-1 resistance

High glucose-induced PKCβ overexpression may reduce GLP-1 responsiveness in endothelial cellsPujadas 2016

—

GI symptoms

—

Nausea, vomiting, diarrhea (common, dose-dependent)Jastreboff 2022

Injection site reaction

—

Mild erythema, pruritus

Pancreatitis risk

—

Rare; discontinue if suspectedZEPBOUND (tirzepatide) injecti 2023

Thyroid C-cell tumours

—

Boxed warning — contraindicated in MEN2 / MTC historyZEPBOUND (tirzepatide) injecti 2023

Hypoglycemia

—

Low as monotherapy; risk with sulfonylureas / insulin

Gallbladder events

—

Increased cholelithiasis

Pregnancy / OB

—

Contraindicated

Diabetic retinopathy

—

Rapid glycemic improvement may transiently worsen

Absolute Contraindications

GLP-1 (7-37)

—

Tirzepatide

·MTC personal or family history; MEN2
·Pregnancy / breastfeeding
·Hypersensitivity to tirzepatide

Relative Contraindications

GLP-1 (7-37)

—

Tirzepatide

·Severe gastroparesis
·History of pancreatitis
·Diabetic retinopathy

05Administration Protocol

Parameter

GLP-1 (7-37)

Tirzepatide

1. Research use only

Native GLP-1(7-37) is not formulated for therapeutic use. Administered IV or SC in experimental protocols to study GLP-1R pharmacology and as reference standard for analogue development.

Commercial: pre-filled pen / vial. Research lyophilised: bacteriostatic water per label.

2. Storage

Lyophilised peptide stored at -20°C or below. Reconstituted solutions should be prepared fresh and used immediately due to rapid degradation.

SQ — abdomen, thigh, or upper arm. Rotate weekly.

3. Clinical alternatives

For therapeutic GLP-1R activation, use FDA-approved long-acting analogues: semaglutide (once weekly), liraglutide (once daily), dulaglutide (once weekly), or exenatide (twice daily or once weekly).

Once weekly, same day. Day change allowed if ≥3 days separate doses.

4. Storage

—

Refrigerate 2–8 °C unopened. Room temp ≤30 °C up to 21 days after first use.

5. Needle

—

Pen-supplied. Research vial: 27–31G insulin syringe.