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Peptide comparison
This page compares retatrutide and tirzepatide as a side-by-side reference, focusing on reconstitution and dosing-reference data drawn from each compound’s available source material. The two are presented together so the documented figures, formats, and frequencies can be viewed in one place. The information below reflects published study data and current regulatory labeling rather than any guidance on use.
Retatrutide
Tirzepatide
Investigational; no FDA/UK/EU marketing approval
FDA-approved prescription for labeled indications
Published Phase 2 human RCT
Current regulator label
Subcutaneous
Subcutaneous
Once weekly
Once weekly
1–12 mg
2.5–15 mg
Retatrutide vs Tirzepatide: at a glance
| Attribute | Retatrutide | Tirzepatide |
|---|---|---|
| Regulatory status | Investigational; no FDA/UK/EU marketing approval | FDA-approved prescription for labeled indications |
| Route | Subcutaneous | Subcutaneous |
| Dosing frequency | Once weekly | Once weekly |
| Published range | 1-12 mg | 2.5-15 mg |
| Evidence basis | Published Phase 2 human RCT | Current regulator label |
| What the source describes | Phase 2 obesity trial tested 1, 4, 8 and 12 mg weekly with study-controlled escalation | Start 2.5 mg weekly; labeled maintenance 5, 10, or 15 mg weekly; max 15 mg |
| Formulation | Arithmetic only. No approved commercial concentration, label, or self-use titration exists. | Commercial Zepbound is supplied pre-mixed in fixed-dose pens/vials. Use actual product concentration; do not invent a reconstitution. |
Every value is quoted from each compound's own labeling or published trial, listed in the sources below. A published range describes what has been studied or labeled - it is not a recommendation, and this page does not advise choosing one compound over the other. There is no valid dose conversion between two different compounds.
What is not established
| Compound | Established dose range | Stated limitation |
|---|---|---|
| Retatrutide | 1-12 mg | Trial doses are not prescribing guidance; formulation and phase-3 protocols may differ. |
| Tirzepatide | 2.5-15 mg | Prescription-only; indication, titration, contraindications, interactions and monitoring are outside this calculator. |
Sources
| Compound | Primary source | Checked |
|---|---|---|
| Retatrutide | New England Journal of Medicine - DOI 10.1056/NEJMoa2301972 | 2026-06-24 |
| Tirzepatide | FDA prescribing information (Tirzepatide) - accessdata.fda.gov | 2026-06-24 |
INTERACTIVE
Model the dosing curve for each
Switch between retatrutide and tirzepatide to see how each builds toward steady state across a full titration. Retatrutide is investigational, so its schedule reflects trial-style escalation — edit any step to match your own plan. Estimate and arithmetic only — not medical advice.
FDA-label titration (Mounjaro / Zepbound). Half-life ≈ 5 days.
One-compartment, first-order weekly-dosing model: k = ln(2) ÷ half-life; each dose decays as e^(−k·t) and all doses are summed (superposition). Shows an estimated relative level, not an absolute plasma concentration (no volume-of-distribution or bioavailability modeling). Titration presets reflect common labeled/trial escalations; retatrutide is investigational. Estimate and arithmetic only — not medical advice. Verify against the product label and with a clinician.
Key differences
The clearest contrast is regulatory status: tirzepatide is an FDA-approved prescription medication for its labeled indications, while retatrutide is investigational and has no FDA, UK, or EU marketing approval. Their evidence tiers differ accordingly, with tirzepatide’s figures coming from a current regulator label and retatrutide’s coming from a published Phase 2 human randomized controlled trial. Both are administered subcutaneously once weekly. The documented ranges differ: tirzepatide’s label spans 2.5 to 15 mg weekly, starting at 2.5 mg with labeled maintenance levels of 5, 10, or 15 mg and a maximum of 15 mg, whereas retatrutide’s Phase 2 obesity trial tested 1, 4, 8, and 12 mg weekly using study-controlled escalation across a 1 to 12 mg range. In short, one set of numbers reflects an approved product label and the other reflects a controlled clinical study.
Reference comparison only. Not medical advice; verify with a clinician, product label, pharmacist, or approved research protocol.
Frequently asked questions
How are retatrutide and tirzepatide administered?
Both are subcutaneous, once-weekly compounds in the sources cited above. Note that tirzepatide is FDA-approved for its labeled indications, while retatrutide is investigational with no marketing approval.
What dose ranges does this comparison reference?
The ranges shown above — retatrutide 1–12 mg from published trials and tirzepatide 2.5–15 mg from the label. These are reference figures, not dosing recommendations.
Can I calculate reconstitution for both here?
Yes — open either calculator from the buttons above to get the concentration (mg/mL), draw volume and U-100 syringe units.
Does this page recommend one over the other?
No. It is a neutral reference drawn from labels and published studies, and it does not assess efficacy, safety, or suitability. Those decisions belong with a licensed prescriber.