To calculate a GLP-3 RT (retatrutide) stock concentration, divide the peptide mass in the vial by the molecular weight (about 4731 g/mol) to get moles, then divide by the reconstitution volume: a 10 mg vial in 1 mL gives 10 mg/mL, which is about 2.11 mM.
This page is concentration arithmetic for in vitro work only. It covers the three vial sizes sold as RT-GLP3 (retatrutide), 10 mg, 20 mg and 30 mg, and how to move from a stock solution to a working concentration for cell-based assays.
What is the formula for stock concentration?
Use the free-peptide molecular weight of 4731.33 g/mol (C221H342N46O68):
- Mass concentration (mg/mL) = vial mass (mg) / volume (mL)
- Moles in the vial (µmol) = vial mass (mg) / 4731.33 x 1000
- Molarity (mM) = moles (µmol) / volume (mL)
For example, 10 mg is 2.114 µmol of peptide; in 2 mL that is 5 mg/mL and 1.057 mM.
Stock concentration table
Values assume the full labelled peptide mass and the free-peptide molecular weight.
| Vial | Moles | In 1 mL | In 2 mL | In 3 mL | In 5 mL |
|---|---|---|---|---|---|
| 10 mg | 2.114 µmol | 10 mg/mL, 2.114 mM | 5 mg/mL, 1.057 mM | 3.33 mg/mL, 0.705 mM | 2 mg/mL, 0.423 mM |
| 20 mg | 4.227 µmol | 20 mg/mL, 4.227 mM | 10 mg/mL, 2.114 mM | 6.67 mg/mL, 1.409 mM | 4 mg/mL, 0.845 mM |
| 30 mg | 6.341 µmol | 30 mg/mL, 6.341 mM | 15 mg/mL, 3.170 mM | 10 mg/mL, 2.114 mM | 6 mg/mL, 1.268 mM |
Choose the reconstitution volume from the solubility information on the batch report or technical datasheet. The compound carries a lipid side chain, so solubility can differ from simpler peptides. Matching solvent to the assay is covered in the Reconstitution Solution product notes and the store's general peptide concentration and reconstitution math guide.
How do you make a working concentration from the stock?
Use C1V1 = C2V2. From a 2.114 mM stock, a 1:100 dilution gives about 21.1 µM, and a further 1:1000 dilution gives about 21.1 nM. Concentration-response experiments typically span several log units, so a serial dilution series built from one stock keeps the relative spacing exact. The worked method is in Stock and Working Solutions: Serial Dilution for In-Vitro Assays.
What corrections should you apply?
- Net peptide content: a vial's labelled mass is not always the measured peptide mass. Where the report gives net content, multiply the labelled mass by the net-content fraction before calculating.
- Counter-ion: if the report states a salt-form molecular weight (a trifluoroacetate form is roughly 114 Da heavier), use that value for the matching mass basis, and do not mix bases.
- Aliquots: divide the stock into single-use aliquots and avoid repeated freeze-thaw cycles.
Related research guides
Research-use note
All materials discussed are supplied for in vitro laboratory research use only, and are not for human or animal use.
