Trial protocols, not adviceRetatrutide is not approved by the FDA. The schedules below describe what researchers gave volunteers in controlled studies. Only a licensed clinician can decide whether any medicine and dose is right for a person.
Retatrutide dosing schedule and titration in phase 3 (TRIUMPH and TRANSCEND)
All phase 3 trials started at 2 mg once weekly and increased the dose every 4 weeks until the assigned maintenance dose was reached. The dose strengths used were 2, 4, 6, 9 and 12 mg.[1][3][7][8]
| Maintenance dose | Schedule | On target dose from |
|---|---|---|
| 4 mg | Weeks 1–4: 2 mg Weeks 5–8: 4 mg | Week 5 |
| 9 mg | Weeks 1–4: 2 mg Weeks 5–8: 4 mg Weeks 9–12: 6 mg Weeks 13–16: 9 mg | Week 13 |
| 12 mg | Weeks 1–4: 2 mg Weeks 5–8: 4 mg Weeks 9–12: 6 mg Weeks 13–16: 9 mg Weeks 17–20: 12 mg | Week 17 |
Week numbers are calculated from the 4-week steps. In TRIUMPH-1, people stayed on their maintenance dose for the rest of the 80-week treatment period.[1]
Retatrutide starting dose
The retatrutide starting dose in every phase 3 trial was 2 mg once weekly for the first 4 weeks.[1][3] Phase 2 tested this directly. In the obesity trial, two arms started at 4 mg and two comparable arms started at 2 mg:[4]
| Target dose | Start 2 mg: weight change | Start 4 mg: weight change |
|---|---|---|
| 4 mg | −16.3% | −17.8% |
| 8 mg | −21.7% | −23.9% |
Weight loss was similar either way, but stomach side effects were highest in the arms that started at 4 mg, and the authors wrote they were "partially mitigated with a lower starting dose."[4] The diabetes trial also compared a 4 → 8 mg "fast" schedule with a 2 → 4 → 8 mg "slow" one and found similar HbA1c results (−1.88% vs −1.99%).[5] These are trial findings, not a recommendation for anyone.
Retatrutide dosage chart: phase 2 obesity trial
The 48-week phase 2 trial in 338 adults with obesity tested more schedules, including two different starting doses.[4][6]
| Arm | Escalation, every 4 weeks | Weight change at 48 weeks |
|---|---|---|
| Placebo | – | −2.1% |
| 1 mg | No escalation | −8.7% |
| 4 mg, start 2 mg | 2 → 4 mg | −16.3% |
| 4 mg, start 4 mg | 4 mg throughout | −17.8% |
| 8 mg, start 2 mg | 2 → 4 → 8 mg | −21.7% |
| 8 mg, start 4 mg | 4 → 8 mg | −23.9% |
| 12 mg, start 2 mg | 2 → 4 → 8 → 12 mg | −24.2% |
Starting at 4 mg instead of 2 mg did not change weight loss much, but it gave the highest rates of stomach side effects. The authors wrote that these were "partially mitigated with a lower starting dose."[4] That is why phase 3 started everyone at 2 mg.
Phase 2 type 2 diabetes trial schedule
A separate 36-week phase 2 trial in 281 people with type 2 diabetes used similar steps.[5]
| Arm | Escalation, every 4 weeks | HbA1c change at 24 weeks |
|---|---|---|
| 0.5 mg | No escalation | −0.43% |
| 4 mg, escalated | 2 → 4 mg | −1.39% |
| 4 mg | 4 mg throughout | −1.30% |
| 8 mg, slow | 2 → 4 → 8 mg | −1.99% |
| 8 mg, fast | 4 → 8 mg | −1.88% |
| 12 mg | 2 → 4 → 8 → 12 mg | −2.02% |
| Placebo | – | −0.01% |
Dose, weight loss and side effects in TRIUMPH-1
Higher maintenance doses gave more weight loss, and also more side effects and more people stopping. TRIUMPH-1, the largest trial, shows the trade-off at each phase 3 dose after 80 weeks:[1]
| Dose | Weight change | Nausea | Vomiting | Dysesthesia | Stopped due to side effects |
|---|---|---|---|---|---|
| 4 mg | −17.6% | 28.6% | 10.6% | 5.1% | 4.1% |
| 9 mg | −23.7% | 38.4% | 22.8% | 12.3% | 6.9% |
| 12 mg | −25.0% | 42.4% | 25.3% | 12.5% | 11.3% |
| Placebo | −3.9% | 14.8% | 4.8% | 0.9% | 4.9% |
Going from 9 mg to 12 mg added about 1.3 percentage points of weight loss but raised the share who stopped treatment from 6.9% to 11.3%. Full results are on the results page and the side effects page.
Retatrutide dosing compared with Zepbound and Wegovy
All three drugs start low and step up every 4 weeks, but the milligram amounts are completely different and cannot be swapped between drugs.
| Retatrutide (trials) | Tirzepatide (Zepbound label) | Semaglutide (Wegovy label) | |
|---|---|---|---|
| Starting dose | 2 mg[1] | 2.5 mg[9] | 0.25 mg[10] |
| Steps | 2 → 4 → 6 → 9 → 12 mg | Up in 2.5 mg steps | 0.25 → 0.5 → 1 → 1.7 → 2.4 mg |
| Interval between steps | Every 4 weeks | At least 4 weeks | Every 4 weeks |
| Maintenance doses | 4, 9 or 12 mg | 5, 10 or 15 mg | 1.7 or 2.4 mg |
| Status | Investigational | FDA-approved | FDA-approved |
Retatrutide's steps are trial protocols; the other two columns are from the FDA labels. How the trial results compare is covered in retatrutide vs tirzepatide and retatrutide vs semaglutide.
How often retatrutide is dosed
Every published trial gave retatrutide once per week, on the same day each week. The weekly dose ranged from 0.5 mg (phase 2 diabetes trial) to 12 mg.[4][5] No trial split the weekly dose into smaller daily injections. The long half-life of about 6 days is what makes weekly dosing possible.[4]
Units chart for the phase 3 dose steps
If a dose is measured from a mixed vial with a U-100 insulin syringe, the number of units depends on the concentration. This chart covers a 10 mg vial. Other vial sizes are on the reconstitution page.
| Dose | 1 mL | 1.5 mL | 2 mL | 2.5 mL | 3 mL |
|---|---|---|---|---|---|
| 2 mg | 20 | 30 | 40 | 50 | 60 |
| 4 mg | 40 | 60 | 80 | 100 | 120 |
| 6 mg | 60 | 90 | 120 | 150 | 180 |
| 9 mg | 90 | 135 | 180 | 225 | 270 |
A 12 mg dose does not fit in a single 10 mg vial. See the 24 mg vial guide for a chart that covers every step.
What is still unknown
- Whether doses above 12 mg were studied. None appear in the published trials.
- Which escalation scheme is best. TRIUMPH-9 is comparing three schemes over 104 weeks, with no results yet.[6]
- What the approved label will say. Doses and schedules can change between trials and final FDA labeling.
Related
- Dosage calculatorConvert any dose to units
- Results by doseWeight loss in each trial
- Side effects by doseNausea, vomiting, dysesthesia and more
Frequently asked questions
What is the retatrutide maintenance dose?
Phase 3 trials assigned people to a maintenance dose of 4, 9 or 12 mg once weekly, reached by the titration schedule above.[1]
What is the retatrutide max dose?
What is the retatrutide dosing schedule?
In phase 3 trials: 2 mg weekly for 4 weeks, then 4 mg, then 6 mg, then 9 mg, then 12 mg, with each step lasting 4 weeks, stopping at the assigned dose (4, 9 or 12 mg).[1]
How long until the 12 mg dose?
Following the phase 3 steps, the 12 mg dose starts in week 17, after four 4-week steps at 2, 4, 6 and 9 mg.
Is the 1 mg dose effective?
In phase 2, 1 mg weekly gave an average weight change of −8.7% at 48 weeks, compared with −2.1% on placebo.[4] Phase 3 trials did not use 1 mg as a maintenance dose.
Sources
- Jastreboff AM et al. Retatrutide for obesity (TRIUMPH-1)
- Lilly: retatrutide delivered powerful weight loss in pivotal phase 3 obesity trial (TRIUMPH-1)
- Lilly: retatrutide delivered weight loss of up to 71.2 lbs in TRIUMPH-4
- Jastreboff AM et al. Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial
- Rosenstock J et al. Retatrutide in people with type 2 diabetes: a phase 2 trial
- Retatrutide studies (NCT04881760, NCT05929066, NCT05931367, NCT06662383, NCT07629401 and others)
- Bellido V et al. Retatrutide in obesity with type 2 diabetes (TRIUMPH-2)
- Bajaj HS et al. Retatrutide in type 2 diabetes (TRANSCEND-T2D-1)
- Zepbound (tirzepatide) prescribing information
- Wegovy (semaglutide) injection prescribing information