GLP3 Reconstitution Calculator

Your calculator assumes the peptide in your vial corresponds to a single known hormone. However, "GLP‑3" is not an official receptor or a new human hormone — humans produce GLP‑1 and GLP‑2, but there is no "GLP‑3" hormone. "GLP‑3" is an informal internet nickname for retatrutide, an investigational drug that simultaneously activates three distinct hormone receptors: GIP, GLP‑1, and glucagon. Your calculator works perfectly for reconstituting retatrutide powder, but the name "GLP‑3" can be misleading because it suggests a single‑receptor peptide, while retatrutide is a complex multi‑agonist with unique pharmacological properties.

Your calculator is built around the assumption that you are reconstituting a vial for frequent, often daily, injections from the same vial, as the "Doses per vial" display shows. The half‑life of retatrutide is approximately 150‑180 hours, or 6 days, which means it reaches a steady state in the body after 4‑5 weeks and maintains therapeutic levels throughout a once‑weekly regimen. The clinical dosing schedule uses a single weekly injection that then sustains activity for the entire week. You should therefore use the calculator to prepare the entire weekly dose at once — not to split it into smaller daily injections — and the "Doses per vial" count will tell you how many weeks one vial lasts, not how many daily injections.

Your calculator's "Doses per vial" assumes full potency and sterility for the entire content of the vial, but retatrutide is an investigational peptide with no manufacturer‑validated stability data for reconstituted solution. General guidance suggests 28 days at 2‑8°C as a practical beyond‑use date, but this is not based on clinical studies. The 28‑day limit is primarily driven by infection risk from repeated vial puncture, not necessarily by chemical degradation. Therefore, the "Doses per vial" number is a mathematical maximum. If your weekly dose is 2 mg and the vial contains 10 mg, the calculator shows 5 doses, but you should never draw the 5th dose after more than 28 days, even if the vial is not empty.

Your calculator assumes that the peptide will completely dissolve in the chosen BAC water volume at neutral pH. However, retatrutide is reported as "slightly soluble" in water and shows only sparing solubility (1‑10 mg/mL) in PBS at pH 7.2. To achieve higher concentrations (e.g., 20‑30 mg/mL), some suppliers recommend ultrasonic treatment or adjusting the pH to 9 with aqueous NH3. If you use the calculator with a small BAC volume (e.g., 1 mL for a 10 mg vial) and the solution remains cloudy, the peptide has not fully dissolved, and the calculated units will be inaccurate. In such cases, you must use a larger BAC volume (even if the calculator marks it as "Usable" rather than "Best") or switch to an alternative solvent.

Your calculator is a point‑in‑time tool: it calculates the units for the dose you enter today. For a study lasting 68‑104 weeks with regular dose increases every 4 weeks, as used in Phase 3 trials, you will need to recalibrate your calculator at each step. For example, if you start with a 10 mg vial reconstituted with 1 mL of BAC water (10 mg/mL), the calculator will show 20 units for a 2 mg dose during weeks 1‑4, but then 40 units for a 4 mg dose during weeks 5‑8 — but your vial may already be partially used, so you must ensure enough solution remains. Your calculator does not have a "remaining volume" tracker, so for lengthy, multi‑stage protocols, consider keeping a separate log of how many units you have withdrawn from each vial.