Retatrutide Dosage Chart UK — Research Reference 2026
Target keywords: "retatrutide dosage", "retatrutide dosage chart", "uk retatrutide", "peptides retatrutide" (combined ~910/mo, currently ranked #60–#81) Suggested URL: /retatrutide-dosage-chart-uk Meta title: Retatrutide Dosage Chart UK 2026 | Research Reference Meta description: Retatrutide dosage chart with reconstitution volumes, titration steps from published studies, half-life and storage — UK research reference, 2026.
Introduction
Retatrutide is a triple-agonist research peptide acting on GLP-1, GIP and glucagon receptors. Of those three pathways, the glucagon component is what separates retatrutide from tirzepatide (dual GIP/GLP-1) and from semaglutide (GLP-1 alone).
This page is a quick-reference dosage chart for UK research customers, drawn from published Phase 1 and Phase 2 trial protocols. It covers reconstitution volumes for every common vial size, weekly titration steps reported in studies, conversion from milligrams to insulin-syringe units, and storage parameters.
For laboratory research use only. Not for human consumption. This is reference information from published literature, not a dosing recommendation.
1. Retatrutide at a glance
| Property | Value |
|---|---|
| Molecular weight | ~4,731 Da |
| Receptor targets | GLP-1, GIP, glucagon |
| Half-life (literature) | ~6 days |
| Dosing frequency in trials | Once weekly |
| Vial sizes commonly supplied | 5 mg, 10 mg, 15 mg, 20 mg |
2. Reconstitution volumes
Reconstitute with bacteriostatic water. The volume you add controls the concentration.
| Vial | BAC water added | Final concentration | Volume per 1 mg |
|---|---|---|---|
| 5 mg | 1 mL | 5 mg/mL | 0.20 mL (20 IU) |
| 5 mg | 2 mL | 2.5 mg/mL | 0.40 mL (40 IU) |
| 10 mg | 1 mL | 10 mg/mL | 0.10 mL (10 IU) |
| 10 mg | 2 mL | 5 mg/mL | 0.20 mL (20 IU) |
| 10 mg | 3 mL | 3.33 mg/mL | 0.30 mL (30 IU) |
| 15 mg | 1.5 mL | 10 mg/mL | 0.10 mL (10 IU) |
| 15 mg | 3 mL | 5 mg/mL | 0.20 mL (20 IU) |
| 20 mg | 2 mL | 10 mg/mL | 0.10 mL (10 IU) |
| 20 mg | 4 mL | 5 mg/mL | 0.20 mL (20 IU) |
"IU" refers to units on a standard U-100 insulin syringe. 1 mL = 100 IU.
Use our peptide calculator to confirm volumes for any vial size or target dose.
3. Titration chart — based on published Phase 2 protocols
The Phase 2 trial of retatrutide (Jastreboff et al., NEJM 2023) used a titration protocol over 24 weeks. Higher arms titrated more aggressively. Reproduced here as a research reference only:
| Week | Conservative arm | Moderate arm | Aggressive arm |
|---|---|---|---|
| 1–2 | 2 mg | 2 mg | 2 mg |
| 3–4 | 2 mg | 4 mg | 4 mg |
| 5–8 | 4 mg | 4 mg | 8 mg |
| 9–12 | 4 mg | 8 mg | 12 mg |
| 13–24 | 4 mg | 8 mg | 12 mg |
Gastrointestinal side effects observed in trial subjects were dose-dependent and most pronounced in the aggressive arm.
4. Dose to volume — 5 mg/mL concentration
If you reconstitute a 10 mg vial with 2 mL of bacteriostatic water (5 mg/mL), use this chart:
| Dose (mg) | Volume (mL) | Insulin units (U-100) |
|---|---|---|
| 0.5 | 0.10 | 10 |
| 1 | 0.20 | 20 |
| 2 | 0.40 | 40 |
| 3 | 0.60 | 60 |
| 4 | 0.80 | 80 |
| 5 | 1.00 | 100 |
5. Dose to volume — 10 mg/mL concentration
If you reconstitute a 10 mg vial with 1 mL of bacteriostatic water (10 mg/mL):
| Dose (mg) | Volume (mL) | Insulin units (U-100) |
|---|---|---|
| 1 | 0.10 | 10 |
| 2 | 0.20 | 20 |
| 4 | 0.40 | 40 |
| 6 | 0.60 | 60 |
| 8 | 0.80 | 80 |
| 10 | 1.00 | 100 |
6. Storage
| State | Temperature | Duration |
|---|---|---|
| Lyophilised, sealed | 2–8 °C | 24+ months |
| Lyophilised, long-term | –20 °C | 36+ months |
| Reconstituted (BAC water) | 2–8 °C | Up to 28 days |
| Reconstituted (sterile water) | 2–8 °C | <24 hours |
Avoid freeze-thaw cycles on reconstituted material. Protect from light. Do not shake — gently swirl.
7. Half-life and weekly dosing
Retatrutide's ~6-day half-life is why published protocols use once-weekly dosing. After a single dose, plasma levels remain measurable for approximately 3 half-lives (~18 days) before falling below assay detection limits in pharmacokinetic studies.
8. Purity and COAs
Every batch we ship has a third-party Certificate of Analysis with:
- HPLC purity ≥99%
- Mass spec confirming ~4,731 Da
- Batch number, date and independent lab signature
9. FAQs
Is retatrutide stronger than tirzepatide? In the Jastreboff Phase 2 trial, retatrutide produced larger weight reductions in subjects than published tirzepatide data, but the two were not compared head-to-head in the same trial. The glucagon agonism is the mechanistic difference.
Can I split a weekly dose into two smaller doses? Published trials used single weekly administrations. Splitting changes the pharmacokinetic profile and isn't reflected in any published protocol.
How long does a 10 mg vial last on a 4 mg weekly research protocol? 2.5 weeks.
What's the difference between retatrutide and tirzepatide? Tirzepatide is a dual agonist (GIP + GLP-1). Retatrutide adds a third — glucagon. See our tirzepatide UK research guide.
10. UK supply
We stock retatrutide in 5 mg, 10 mg, 15 mg and 20 mg vials, all with batch-matched HPLC + MS Certificates of Analysis. Next-day UK dispatch.
View retatrutide product page →
Internal links to add at publish-time
- /retatrutide-uk
- /product/tirzepatide
- /peptide-reconstitution-guide
- /calculator
- /coa
- /tirzepatide-uk-research-guide-2026 (once published)
Schema markup to add
Article + FAQPage JSON-LD. Consider HowTo schema for the reconstitution section.