Written by PX1 Research Team
PX1 chemists and research educators with hands-on experience in US-based peptide manufacturing, HPLC / mass-spectrometry lot testing, and endotoxin QC. All content is citation-backed and peer-reviewed for accuracy.
Retatrutide Dosage Chart (2026): Titration Schedule and Volume Table
Research Guide
Reviewed By
PX1 QC — Analytical Chemistry Team
Every article is reviewed by PX1's in-house analytical team for accuracy on mechanism, dosing ranges reported in the literature, and lab-handling guidance. We do not publish clinical or medical advice.
Quick answer
A complete retatrutide dosage chart built from published Phase 2 titration data, with reconstitution volumes in mL and insulin-syringe units for 5 mg/mL and 10 mg/mL preparations.
Key takeaways
- Lot-specific HPLC purity ≥99.0% with the chromatogram attached
- LC-MS mass confirmation against the expected 4731.6 Da
- LAL endotoxin reported in EU/mg
- Karl Fischer moisture within spec
How this chart was built
Retatrutide (LY-3437943) is a GLP-1 / GIP / glucagon triple agonist still in clinical development. Every number below is derived from the published Phase 2 obesity protocol (Jastreboff et al., NEJM 2023), which evaluated once-weekly doses of 1, 4, 8 and 12 mg over 48 weeks with a stepped titration. This is a laboratory reference, not a dosing recommendation.
The dosage chart
| Phase (weeks) | Weekly dose | Volume at 5 mg/mL | Volume at 10 mg/mL |
|---|---|---|---|
| 1–4 | 1 mg | 0.20 mL (20 units) | 0.10 mL (10 units) |
| 5–8 | 2 mg | 0.40 mL (40 units) | 0.20 mL (20 units) |
| 9–12 | 4 mg | 0.80 mL (80 units) | 0.40 mL (40 units) |
| 13–16 | 6 mg | 1.20 mL | 0.60 mL (60 units) |
| 17–20 | 8 mg | 1.60 mL | 0.80 mL (80 units) |
| 21–24 | 10 mg | 2.00 mL | 1.00 mL |
| 25+ | 12 mg | — | 1.20 mL |
Units refer to an insulin syringe graduated in 100 units per 1 mL.
Two things researchers get wrong most often when reading a chart like this:
- The chart is not the protocol. Trials held each step for roughly four weeks before escalating. Compressing the schedule is what generated the GI adverse-event signal in the fast-titration arms.
- The volume column depends entirely on your reconstitution. A 10 mg vial reconstituted with 2 mL is 5 mg/mL; the same vial with 1 mL is 10 mg/mL. Recalculate every time the fill or diluent changes.
The only formula you need
`volume (mL) = target dose (mg) ÷ concentration (mg/mL)`
And to get concentration:
`concentration (mg/mL) = vial fill (mg) ÷ diluent volume (mL)`
Worked example: a 15 mg vial reconstituted with 1.5 mL of bacteriostatic water gives 10 mg/mL. A 6 mg step is 6 ÷ 10 = 0.60 mL, which is 60 units on a U-100 insulin syringe.
Run your own numbers with the reconstitution calculator.
Why titration is structured the way it is
The glucagon-receptor arm of retatrutide's activity increases energy expenditure but also amplifies the gastrointestinal profile shared by the incretin class. Published data show adverse events cluster around escalation weeks, not steady-state weeks — which is why every trial arm used a hold period rather than continuous ramping.
Half-life and interval
A fatty-acid side chain binds serum albumin and extends retatrutide's half-life to approximately six days, which is what makes once-weekly administration the standard interval across all published protocols. Splitting a weekly dose into smaller more frequent fractions has no published pharmacokinetic basis.
Documentation to verify before any dosing work
- Lot-specific HPLC purity ≥99.0% with the chromatogram attached
- LC-MS mass confirmation against the expected 4731.6 Da
- LAL endotoxin reported in EU/mg
- Karl Fischer moisture within spec
PX1 publishes all four per lot at /purity-reports. Current retatrutide lots are listed in the catalog.
Research use only. Not for human consumption. Not intended to diagnose, treat, cure, or prevent any disease.