What the Retatrutide Peptide Calculator Does
Retatrutide (LY3437943) is an investigational once-weekly injectable peptide being studied by Eli Lilly. It acts on three receptors at once: GLP-1, GIP and glucagon. Like other peptides supplied as a freeze-dried powder, it has to be dissolved before a dose can be measured, and the strength of the solution depends entirely on how much water is added.
That is where this tool helps. It takes the vial amount, the water volume and the dose your clinician gave you, then returns the volume in mL and the matching mark on a U-100 insulin syringe. Some people search for it as a "reta calculator" or, misspelled, a "rera calculator" — it is the same math.
Retatrutide Status: Read This First
Retatrutide is not approved by the FDA or any other major regulator. It is available only inside clinical trials. Products sold online as "retatrutide peptide" or "for research use only" are unregulated, and their contents, purity and sterility are unknown. Drugs.com explains the risks of retatrutide sold online, and the Wikipedia entry on retatrutide summarises its development history.
This page does not recommend a dose, a titration schedule or a supplier. If you are in a trial or under medical care, use the numbers from your study protocol or prescriber, and treat this page as a cross-check, never as the source of a dose.
Retatrutide Calculator Formula
The math is identical to every other peptide. Three steps take you from vial label to syringe mark:
concentration (mg/mL) = vial (mg) ÷ water (mL)
volume (mL) = dose (mg) ÷ concentration
units = volume (mL) × 100
Retatrutide doses are written in milligrams, so keep the dose selector on mg. Choosing mcg by mistake makes the result 1,000 times too small, which is the most common error in any peptide calculation.
Retatrutide Peptide Calculator Example
Suppose a 10 mg vial is reconstituted with 2 mL of bacteriostatic water and the prescribed dose is 1 mg. Here is the working:
- Concentration: 10 mg ÷ 2 mL = 5 mg/mL.
- Volume: 1 mg ÷ 5 mg/mL = 0.2 mL.
- Units: 0.2 mL × 100 = 20 units.
- Doses per vial: 10 mg ÷ 1 mg = 10.
The same 1 mg dose from a 20 mg vial with 2 mL of water would be 10 units, because that solution is twice as strong. Always recalculate when the vial size or water volume changes.
Retatrutide Units Chart by Vial Size
Units per 1 mg of retatrutide for common vial sizes and water volumes. Multiply by your dose in mg to read off your own figure.
| Vial | 1 mL water | 2 mL water | 3 mL water |
|---|---|---|---|
| 5 mg | 20 units per mg | 40 units per mg | 60 units per mg |
| 10 mg | 10 units per mg | 20 units per mg | 30 units per mg |
| 20 mg | 5 units per mg | 10 units per mg | 15 units per mg |
| 30 mg | 3.3 units per mg | 6.7 units per mg | 10 units per mg |
If a dose comes out under 5 units, more water on the next vial makes it easier to measure. You can plan that in advance with the peptide reconstitution calculator, and track how long a vial lasts with the peptide dosage calculator.
Retatrutide Research at a Glance
In a 48-week phase 2 trial in adults with obesity, retatrutide produced average weight reductions of up to about 24%, with gastrointestinal effects such as nausea and diarrhoea being the most common side effects, according to a review in the NIH PMC archive. Larger phase 3 trials followed, so check the latest regulatory status before relying on any figure. Results from trials do not make unregulated products safe.
Weight-loss medicines work best alongside a sensible calorie target. Our TDEE calculator estimates daily energy needs and protein intake.
Retatrutide Peptide Calculator FAQ
How many units is 1 mg of retatrutide?
It depends on the concentration. From a 10 mg vial with 2 mL of water, 1 mg is 20 units. From a 20 mg vial with 2 mL, it is 10 units.
Is a rera calculator the same as this retatrutide calculator?
Yes. "Rera" is a common misspelling of "reta", short for retatrutide. The calculation is the same.
Does this retatrutide peptide calculator recommend doses?
No. It converts a dose you already have into syringe units. Doses must come from a clinical-trial protocol or a licensed prescriber.
Can I use the retatrutide calculator for other peptides?
Yes. The formula is universal. For any other compound, the main peptide calculator does the same job without retatrutide presets.
This retatrutide peptide calculator is an educational arithmetic tool. Retatrutide is an investigational drug and is not approved for prescription use. Nothing here is medical advice; read our medical disclaimer and how our formulas are checked.