Retatrutide Dosage Calculator: Complete Dosing & Reconstitution Guide
Use this calculator for concentration and volume arithmetic. The research discussion separates trial dose groups from treatment instructions; retatrutide remains investigational.
This tool converts an amount you enter into liquid volume. It does not select a dose or titration schedule. Use the instructions and concentration for your actual product; it does not convert pen clicks, tablets, or powder-mixing instructions.
Select Medication
Your product and entered amount
Enter mg per administration and the labeled mg/mL, not the total mg in the container. Full-vial solution volume is optional and means liquid volume, not container capacity.
Volume calculation
Enter an amount and labeled concentration to calculate volume.
Week tracking
Recordkeeping only: changing the week or date never changes your entered amount. A future start date displays week 1.
Current Week 1
Full-Vial Supply Estimate
Enter valid amount, concentration, and full-vial solution volume to estimate supply. Values must be within the calculator’s numerical range.
Assumes a full vial now, one administration per week, no dose changes and no handling losses. Counts complete portions only. Not a refill date, shelf-life estimate, or authorization to keep a vial in use.
Titration: product-specific references
A calendar week alone does not determine a dose. Product, indication, response and tolerability matter. Ozempic and Wegovy do not share one interchangeable dosing schedule; a branded product’s label also does not establish the instructions for a compounded vial.
Retatrutide is not Mounjaro. Mounjaro contains tirzepatide; Lilly describes retatrutide as investigational. The retatrutide option provides arithmetic, not a recommended treatment schedule. References checked September 8, 2026.
Arithmetic verification is separate from clinical review.
Understanding Retatrutide Dosing Tiers
The 2023 randomized phase 2 obesity trial assigned participants to distinct weekly dose groups. It did not give everyone a 1 → 4 → 8 → 12 mg ladder. Trial doses are evidence about the study, not instructions for a commercial vial.
Phase 2 Dose Groups, Not a Universal Schedule
| Assigned group | Initial dose in that trial |
|---|---|
| 1 mg | 1 mg |
| 4 mg | 2 mg or 4 mg, in separate groups |
| 8 mg | 2 mg or 4 mg, in separate groups |
| 12 mg | 2 mg |
Emerging evidence remains relevant: Lilly reported phase 3 TRIUMPH-1 results in May 2026, including 28.3% average weight reduction at 80 weeks in the 12 mg group using the efficacy estimand. This sponsor-reported result and the phase 2 24.2% result at 48 weeks describe different studies and time points; one does not simply replace the other or predict an individual outcome.
Reconstitution Math for Compounded Peptides
Reconstitution means dissolving a powder in the product-specified diluent. Arithmetic cannot establish the correct diluent, sterility, identity, stability or suitability of a preparation.
Final concentration (mg/mL) = total mass (mg) ÷ final solution volume (mL). Final volume is the resulting liquid volume, not the container capacity.
Standard Reconstitution Scenarios
These retained examples illustrate equal concentrations, not standard retatrutide formulations or mixing recommendations:
- 10 mg in 2 mL final solution = 5 mg/mL.
- 5 mg in 1 mL final solution = 5 mg/mL.
- 15 mg in 3 mL final solution = 5 mg/mL.
Calculating Doses from Your Reconstitution
Volume (mL) = entered amount (mg) ÷ actual concentration (mg/mL). For example, 4 mg ÷ 5 mg/mL = 0.8 mL. This converts the supplied numbers; it does not establish that 4 mg is appropriate.
Syringe Unit Conversions
U-100 and U-40 describe different insulin concentration scales. The number of scale units is not the number of graduation lines. Inspect the actual device and instructions.
Standard Syringe Markings
| Scale | Volume per scale unit | 0.5 mL equivalent |
|---|---|---|
| U-100 | 0.01 mL | 50 units |
| U-40 | 0.025 mL | 20 units |
| mL scale | Read the stated graduation interval | 0.5 mL |
Converting Between Syringe Types
As a second arithmetic example, 0.8 mL corresponds to 80 U-100 units or 32 U-40 units. This does not make devices interchangeable. Neither a scale label nor this calculation establishes capacity or achievable measurement precision; the calculator above uses U-100 only.
Weight-Based vs Fixed Dosing
Fixed Dose Groups in Research
The phase 2 study assigned mg dose groups rather than one body-weight formula. Participants were not all assigned the same final amount.
Weight-Based Dosing
An mg/kg calculation can multiply weight by a specified factor, but mathematics alone cannot supply that factor. The former 0.1 mg/kg example on this page was not a validated retatrutide dosing rule. It should not be used to select an amount.
Titration Schedule & Injection Timing
Why There Is No Universal 12-Week Timeline Here
The former 1, 4, 8 and 12 mg calendar conflated study groups with a single escalation schedule. The study protocol and assigned group determine a trial participant’s instructions. The week tracker above is recordkeeping only and never changes an entered amount.
Injection Day Best Practices
For a study participant, timing, device use, preparation, storage and missed-dose instructions come from the study team. A generic before-meal rule or 15-minute warming rule cannot be established from the volume calculation. Recording the supplied instructions and any symptoms can help resolve questions.
When to Hold or Delay Escalation
Common Reasons to Delay Escalation
Persistent vomiting, severe abdominal pain or palpitations call for prompt clinical assessment. The calculator cannot determine whether an amount should be held, reduced or stopped, or how long an interruption should last.
Dose Hold Protocol
Ask the study team for explicit instructions. “Hold” can mean different things; it must not automatically be interpreted as continuing the same weekly amount for one or two additional weeks.
Common Reconstitution Errors to Avoid
Top Reconstitution Mistakes
- Confusing mass with concentration: 10 mg in 2 mL is 5 mg/mL, not 10 mg/mL.
- Confusing volume with capacity: a 3 mL container does not prove it contains 3 mL of solution.
- Assuming a universal diluent: bacteriostatic water is not saline and is not automatically the specified diluent for every product.
- Assuming a universal storage rule: use formulation-specific instructions; refrigeration or a preservative does not establish a discard date.
- Confusing U-40 and U-100: the same number of units represents different volumes on these scales.
Dosage Calculator Tools & Resources
Calculators convert supplied numbers; they cannot verify a vial’s identity or contents. Independently check the arithmetic against the stated concentration and supplied instructions. A correct calculation does not select a treatment amount.
For more context, see our guides on retatrutide dosing evidence, trial dosing schedules, and general peptide dose calculations. For preparation terminology and common errors, read our peptide reconstitution guide.
Compare with tirzepatide dosing.
Peptides for Weight LossComplete weight loss peptide guide.
Which GLP-1 is BestCompare all GLP-1 options.
Frequently Asked Questions
Trial participants follow their assigned study instructions. The 2023 phase 2 obesity trial had separate 1, 4, 8 and 12 mg groups; it did not escalate every participant from 1 to 12 mg. The calculator does not generate a trial regimen.
As arithmetic, 10 mg in a final solution volume of 2 mL equals 5 mg/mL. At that concentration, 4 mg corresponds to 0.8 mL. This does not specify a diluent, validate an amount or establish syringe graduation size.
U-40 means 40 scale units per mL: one unit is 0.025 mL. U-100 means 100 units per mL: one unit is 0.01 mL. Therefore 0.5 mL is 20 U-40 units or 50 U-100 units. Capacity and graduation spacing are separate properties; this calculator displays U-100 only.
The phase 2 obesity study used assigned mg dose groups, not a weight-derived treatment formula. An mg/kg arithmetic example does not establish an appropriate retatrutide regimen. Ask the trial team about study-specific instructions.
Do not infer an adjustment from this calculator. Trial-specific instructions govern dose interruptions, reductions and escalation; symptoms require individualized assessment rather than a generic tier rule.
First confirm the actual contents and concentration with the supplier or study team. Mathematically, 10 mg in 1 mL is 10 mg/mL, while 10 mg in 2 mL is 5 mg/mL. A container capacity or unexpected fill level alone is not enough to establish concentration.
There is no universal acceptable error of plus or minus 0.1 mL. Its relative size depends on the intended volume, and its clinical significance depends on the product and amount. Use product-specific preparation instructions and appropriate measuring equipment.