GLP-1 peptides — the incretin class
Glucagon-like peptide-1 receptor agonists are the most-studied metabolic peptides of the last decade. This page covers the receptor pharmacology, the differences between mono-, dual-, and triple-agonist designs, and the practical reconstitution and stability characteristics of the specific molecules researchers ask about most: semaglutide, tirzepatide, retatrutide, cagrilintide, and survodutide.
The incretin system in one paragraph
GLP-1 is an endogenous incretin hormone secreted by intestinal L-cells after a meal. It binds the GLP-1 receptor (a class B G-protein-coupled receptor) on pancreatic β-cells to potentiate glucose-dependent insulin release, on α-cells to suppress glucagon, on gastric smooth muscle to slow gastric emptying, and on hypothalamic nuclei to reduce food intake. Native GLP-1 has a half-life of about 1.5–2 minutes because plasma DPP-4 cleaves it almost immediately. Every modern GLP-1 research peptide is a structural analog engineered to resist DPP-4, extend half-life by orders of magnitude, and (in the newer designs) co-target related receptors (GIP, glucagon, amylin).
Mono- vs dual- vs triple-agonist designs
| Compound | Receptor targets | Half-life | Research dose range |
|---|---|---|---|
| Semaglutide | GLP-1 (mono) | ~165 h (≈ 1 week) | 0.25 → 2.4 mg weekly (titrated) |
| Tirzepatide | GLP-1 + GIP (dual) | ~120 h (≈ 5 days) | 2.5 → 15 mg weekly (titrated) |
| Retatrutide | GLP-1 + GIP + glucagon (triple) | ~144 h (≈ 6 days) | 2 → 12 mg weekly (titrated) |
| Survodutide | GLP-1 + glucagon (dual) | ~144 h (≈ 6 days) | 0.6 → 6 mg weekly (titrated) |
| Cagrilintide | Amylin / calcitonin receptors | ~159 h (≈ 6.5 days) | 0.16 → 4.5 mg weekly (often co-administered with semaglutide as "CagriSema") |
Pharmacokinetic values are typical clinical-trial steady-state numbers and vary by lot, subject, and route.
Why dual and triple agonism matters
GIP (glucose-dependent insulinotropic peptide) and glucagon receptors complement GLP-1 in metabolically relevant ways. GIP co-agonism appears to amplify insulin response and modulate adipose-tissue handling. Glucagon co-agonism increases energy expenditure and hepatic fatty-acid oxidation — a pathway pure GLP-1 agonists don't touch. In research-model comparisons:
- GLP-1 mono (semaglutide) → strong appetite suppression, modest energy-expenditure effect.
- GLP-1 + GIP (tirzepatide) → typically larger weight-loss effect than mono-agonism at equivalent doses.
- GLP-1 + GIP + glucagon (retatrutide) → largest weight-loss magnitudes reported to date in phase-2 trials.
- GLP-1 + glucagon (survodutide) → emphasis on hepatic steatosis pathways alongside weight effects.
- Amylin (cagrilintide) → satiety and gastric-emptying axis; complementary to GLP-1, hence stacked dosing.
Reconstitution math (worked example)
GLP-1 vials are usually labeled in milligrams of peptide. To compute the volume of bacteriostatic water to add for a clean dose-per-tick schedule on a U-100 insulin syringe:
1 mL on a U-100 syringe = 100 units → 1 unit = 10 µL
Example — 5 mg semaglutide vial, target 0.25 mg dose:
- Add 2.5 mL BAC water → concentration = 2.0 mg/mL.
- 0.25 mg ÷ 2.0 mg/mL = 0.125 mL = 12.5 units on the syringe.
- Same vial titrated to 0.5 mg → 25 units. 1.0 mg → 50 units. 2.0 mg → entire vial in two draws.
The full per-peptide reconstitution math (including tirzepatide and retatrutide vial sizes) lives in the dosage protocols guide.
Storage and stability
Lyophilized GLP-1 peptides are stable at −20 °C for 24+ months. Reconstituted in bacteriostatic water and refrigerated at 2–8 °C, semaglutide and tirzepatide remain analytically stable for 28–56 days; retatrutide and survodutide are similar. CagriSema combinations should be treated by the shorter of the two component shelf-lives. The full cold-chain protocol (light, freeze–thaw, draw-count) is in the storage & handling guide.
Safety, risks & legal notice
Read before ordering or conducting any research
For laboratory research only
Every compound described on this page is sold and provided strictly as a research-grade reagent for in-vitro and animal-model studies. These products are not intended for human consumption, cosmetic use, dietary supplementation, or any clinical or therapeutic application. By purchasing, you represent that you are a qualified researcher, laboratory, or educational institution with appropriate facilities and oversight.
Not FDA-approved or evaluated
Some compounds in this class have limited regulatory approvals for specific indications (semaglutide (Type 2 diabetes and obesity) and tirzepatide (Type 2 diabetes and obesity)). However, the research-grade materials supplied here are not manufactured, labelled, or verified for those approved uses, and we make no claims regarding their safety or efficacy outside laboratory research.
No medical, clinical, or dosing advice
Dr Jays Peptides does not employ physicians, pharmacists, or clinical researchers. Nothing on this page — including dosage figures, reconstitution math, or mechanism descriptions — constitutes medical advice, a prescribing recommendation, or instructions for self-administration. If you are considering any peptide for personal use, consult a licensed healthcare provider who can evaluate your individual risk factors, medication interactions, and monitoring needs.
Class-specific risk signals
- Gastrointestinal: nausea, vomiting, diarrhea, and constipation are dose-dependent and common across the class; they can lead to dehydration and electrolyte disturbances in research subjects.
- Gallbladder disease: cholelithiasis and cholecystitis rates are elevated in clinical trials of GLP-1 receptor agonists.
- Thyroid C-cell tumors: dose-dependent medullary thyroid carcinoma (MTC) and C-cell hyperplasia were observed in rodent carcinogenicity studies with semaglutide and liraglutide; relevance to humans is unknown but constitutes a theoretical risk signal.
- Pancreatitis: acute pancreatitis cases have been reported in post-marketing surveillance and clinical trials; any sudden severe abdominal pain in a research model should trigger immediate evaluation.
- Hypoglycemia: when studied alongside insulin or sulfonylureas, GLP-1 agonists increase hypoglycemia frequency.
- Gastric emptying: slowed gastric motility may alter absorption kinetics of co-administered compounds in research protocols.
General risk factors
- Purity and contamination: Research peptides are not manufactured to pharmaceutical-grade GMP standards. Even high-purity lots may contain trace endotoxins, residual solvents, or unrelated peptide sequences.
- Stability and degradation: Improper storage, repeated freeze–thaw cycles, or use beyond recommended reconstitution windows can produce degraded products with unknown toxicology.
- Immunogenicity: Foreign peptides can elicit antibody responses; repeated administration may cause allergic reactions or neutralizing antibodies that alter pharmacokinetics in unpredictable ways.
- Drug interactions: Peptides may potentiate or antagonize prescription medications, herbal supplements, or other research compounds. No systematic interaction data exists for most of these molecules.
- Pregnancy, lactation, and pediatric populations: Zero safety data. Absolute contraindication for use in these populations.
Legal status & buyer responsibility
The legal status of research peptides varies by country, state, and municipality. It is the buyer's sole responsibility to understand and comply with all applicable laws, regulations, and institutional policies in their jurisdiction before ordering. Dr Jays Peptides ships products with accurate customs declarations; buyers are responsible for any import duties, inspections, or seizures. We reserve the right to cancel any order where we believe the buyer lacks legitimate research intent or where shipment would violate local law.
Limitation of liability: To the maximum extent permitted by law, Dr Jays Peptides and its affiliates, suppliers, and agents disclaim all liability for any injury, illness, adverse reaction, or loss arising from the purchase, handling, or use of any product described on this page. This includes liability for negligence, product defect, mislabeling, or failure to warn. By proceeding with a purchase, you agree to indemnify and hold harmless Dr Jays Peptides from any claims, damages, or expenses related to your research activities.