Retatrutide Dosage Chart: Trial Titration Schedule
Retatrutide is a once-weekly triple agonist that produced the largest weight-loss numbers seen in any GLP-1-class trial so far. It is also still investigational, with no FDA-approved label and no official prescribing dose. This chart documents the titration schedule the trials actually used, the reconstitution math behind it, and how the doses map to the weight-loss data, so the numbers floating around online have a verifiable source.
Retatrutide Trial Dosage Chart
Across the Phase 2 obesity study and the Phase 3 TRIUMPH program, retatrutide was escalated in four-week steps to a maximum of 12 mg once weekly. The table below shows the canonical ramp. Starting points varied by trial arm, and the Phase 2 study (Jastreboff et al., NEJM 2023) began some groups at 1 mg.
| Weeks | Weekly Dose | Phase | Purpose |
|---|---|---|---|
| 1–4 | 2 mg (1 mg in some arms) | Initiation | Lowest step; lets the gut adapt before escalation |
| 5–8 | 4 mg | Early titration | Maximum dose for the lowest-dose trial arm |
| 9–12 | 8 mg | Mid titration | Maximum dose for the middle trial arm |
| 13+ | 12 mg | Maximum | Highest studied dose; used in TRIUMPH-1 |
Note the structure: the trials did not push everyone to 12 mg. They ran separate arms that stopped at 4 mg, 8 mg, or 12 mg, which is how the dose-response relationship was measured. For a narrative walk-through rather than a table, see our retatrutide dosing guide and retatrutide dosing schedule.
How the Titration Schedule Works
Every step in the chart lasts about four weeks. The reason is tolerability, not efficacy. GLP-1 and glucagon receptor activity slows gastric emptying and blunts appetite, and a sudden jump in dose produces a spike in nausea and vomiting. The four-week hold lets receptor signaling reach a steady state before the next increase, which is the same titration logic behind tirzepatide and semaglutide.
People who reacted poorly to a step held longer before advancing. The starting dose matters here: beginning too high is the fastest route to dropping out over GI distress. Faster ramps were not shown to improve weight loss; they mostly increased side effects.
Reconstitution and Concentration Reference
Trial sites used prepared, dose-controlled product. Outside a trial, retatrutide is sold as a lyophilized powder that must be reconstituted with bacteriostatic water, and this is where the largest dosing errors happen. The final concentration is set entirely by how much water you add, and that fixes how many units on an insulin syringe correspond to a milligram dose.
| Vial Size | BAC Water Added | Concentration | 2 mg dose = | 12 mg dose = |
|---|---|---|---|---|
| 10 mg | 1 mL | 10 mg/mL | 20 units | n/a (exceeds vial) |
| 10 mg | 2 mL | 5 mg/mL | 40 units | n/a (exceeds vial) |
| 20 mg | 2 mL | 10 mg/mL | 20 units | 120 units (over 100u syringe) |
On a standard U-100 insulin syringe, one "unit" is 0.01 mL, so 100 units equals 1 mL. A 12 mg dose at 10 mg/mL would need 1.2 mL, more than a single 100-unit syringe holds. That mismatch is a frequent source of error. Use the calculator below, and cross-check the method in our reconstitution guide and peptide reconstitution calculator.
Peptide Reconstitution Calculator
Calculate concentrations and dosing volumes for peptide reconstitution
Calculation Results
Concentration
25.00
mcg per unit
Volume to Draw
10.0
units per dose
Doses per Vial
20.0
total doses
Vial Duration
20
days
Syringe Fill Indicator
Vial Label Generator
Retatrutide
25.00 mcg/unit
Reconstituted: 2026-06-21
Expires: 2026-07-19
Disclaimer: This calculator is for research and educational purposes only. It is not medical advice. Always consult with a healthcare professional before using any peptide product. Verify all calculations independently.
Dose vs Weight-Loss Response
Retatrutide showed a clean dose-response curve, which is why the 12 mg dose draws the most attention. In the 48-week Phase 2 obesity trial, the 12 mg arm lost about 24% of body weight. In the larger Phase 3 TRIUMPH-1 trial reported in May 2026, the 12 mg dose averaged roughly 28.3% reduction at 80 weeks, with a large share of participants exceeding 30%.
| Max Weekly Dose | Approx. Weight Loss (Phase 2, 48 wk) |
|---|---|
| 4 mg | ~17% |
| 8 mg | ~21% |
| 12 mg | ~24% |
The numbers climb with dose but so do side effects, which is the trade-off the titration ramp is built around. More detail on outcomes sits in our retatrutide weight loss guide.
How Retatrutide Doses Compare to Other GLP-1 Drugs
Milligrams do not transfer between these drugs. Each molecule has different receptor targets and potency, so a dosage chart for one says nothing about the right dose of another.
| Drug | Receptor Targets | Max Studied / Approved Dose |
|---|---|---|
| Retatrutide | GIP + GLP-1 + glucagon | 12 mg weekly (investigational) |
| Tirzepatide | GIP + GLP-1 | 15 mg weekly (approved) |
| Semaglutide | GLP-1 | 2.4 mg weekly (approved) |
The third receptor, glucagon, is what separates retatrutide from tirzepatide. See retatrutide vs tirzepatide and retatrutide vs semaglutide for the full comparison.
Side Effects by Dose Level
Side effects track dose. At the low steps (2–4 mg), most people report mild, intermittent nausea. At 8 mg and 12 mg, nausea, vomiting, and diarrhea become more frequent and more intense, especially in the week after a dose increase. The trials also recorded dose-dependent increases in resting heart rate, and because the glucagon receptor can nudge blood glucose upward, glycemic markers were monitored. Our retatrutide side effects guide breaks these down.
Why There Is No Official Prescribing Dose Yet
A dosage chart is normally anchored to an FDA-approved label that specifies the starting dose, the titration intervals, and the maximum. Retatrutide has none of that. Until Lilly files and the FDA reviews the TRIUMPH data, every "dose" is a trial protocol, not an approved instruction. That gap is why online charts contradict each other and why product sold outside trials has no verified concentration. The honest version of this chart is: here is what the studies did, under supervision, with controlled material.
Related Guides
Frequently Asked Questions About Retatrutide
The published trials used a four-week step-up ramp: roughly 2 mg once weekly for weeks 1-4, 4 mg for weeks 5-8, 8 mg for weeks 9-12, and 12 mg from week 13 onward. The Phase 2 obesity study (Jastreboff et al., NEJM 2023) started some arms as low as 1 mg and tested 4 mg, 8 mg, and 12 mg maximum doses. Exact starting points varied by trial arm. None of this is an approved or prescribable regimen; retatrutide remains investigational.
12 mg once weekly is the highest dose carried through the major obesity trials, including the Phase 3 TRIUMPH-1 program. In TRIUMPH-1, the 12 mg arm produced an average of about 28.3% body-weight reduction at 80 weeks. Higher doses have not been established as safe or more effective in completed pivotal trials.
In the trials, each titration step lasted about four weeks before the next increase. That interval gives the gut time to adapt and limits nausea and vomiting, the same logic used for tirzepatide and semaglutide titration. Some people who tolerate the drug poorly stayed longer at a step. Faster escalation raises the rate of gastrointestinal side effects.
No. As of mid-2026 retatrutide is not FDA approved. Eli Lilly is expected to file for approval after completing the TRIUMPH Phase 3 program, with a realistic approval window in 2027 and commercial availability in 2028. There is no approved label, no commercial pen, and no sanctioned prescribing dose. Material sold as retatrutide outside a clinical trial is unapproved.
Lyophilized peptide has to be mixed with bacteriostatic water before it can be measured. The final concentration depends on how much water you add to the vial, and that determines how many units on an insulin syringe equal a given milligram dose. The concentration table and calculator on this page show the math, but reconstitution accuracy is exactly where dosing errors and contamination risk concentrate.
They are not interchangeable on a milligram basis. Tirzepatide tops out at 15 mg weekly and hits two receptors (GIP and GLP-1). Retatrutide tops out at 12 mg in trials and adds a third target, the glucagon receptor, which drives extra energy expenditure. A 12 mg retatrutide dose and a 15 mg tirzepatide dose are different molecules with different potency, so you cannot convert one to the other.
Gastrointestinal effects dominate and scale with dose: nausea, vomiting, diarrhea, and constipation are most common during dose increases. Higher doses in the trials also showed dose-dependent increases in heart rate. Because the glucagon arm can raise blood glucose, trial protocols monitored glycemic markers. These were research settings with medical oversight that self-directed use does not have.
Because there is no official label to anchor them. Different charts pull from different trial arms, mix Phase 2 and Phase 3 protocols, or invent "microdosing" schedules with no trial basis. When a chart cites a specific number without a trial source, treat it skeptically. The numbers on this page map to the published Jastreboff Phase 2 study and the TRIUMPH program.
The only sanctioned access is enrollment in a clinical trial, where dosing, sourcing, and monitoring are controlled. Outside that, product purity, true concentration, and sterility are unverified, and there is no clinician adjusting the dose to your response. This page documents what the trials did; it is not a protocol to copy at home.