Table of Contents
- What Is Retatrutide and How Does It Work?
- Retatrutide Dosage Chart
- Why Does the Starting Dose Begin at 2 mg?
- How Much Weight Did Each Dose Deliver?
- The 4 mg Dose Is the One People Overlook
- Retatrutide Results Across the Other Trials
- Side Effects by Dose
- What Would Change Someone's Dose?
- Where Retatrutide Stands with the FDA
- What the Chart Does Not Cover
- Bottom Line
Key Takeaways
- The retatrutide starting dose is 2 mg once weekly, not 1 mg as some charts claim.
- Doses rise every four weeks on a fixed escalation schedule.
- Phase 3 studied three target doses: 4 mg, 9 mg, and 12 mg.
- The maximum dose is 12 mg, which produced about 28% average weight loss over 80 weeks.
- The 4 mg target reached 19% body weight reduction with fewer people quitting than in the placebo group.
- Lilly plans to file for FDA approval in Q1 2027 after five successful Phase 3 trials.
Retatrutide is an injectable weight loss drug still being developed by Eli Lilly. There is no official dosing information yet because the FDA has not approved it, so every number below comes from clinical trial protocols instead of a prescribing label.
That said, the trials are consistent. Every Phase 3 study used the same retatrutide dosing schedule: 2 mg once weekly to start, then a step up every four weeks until reaching an assigned target.
Below is that schedule, what each dose produced, and why the climb is spaced the way it is.
What Is Retatrutide and How Does It Work?
Retatrutide is a once-weekly injection being studied as an obesity treatment and for type 2 diabetes. What sets it apart is how many hormone pathways it switches on at once.
Retatrutide activates GIP, GLP-1, and glucagon receptors at the same time:
- GIP (glucose-dependent insulinotropic polypeptide) helps manage blood sugar
- GLP-1 slows digestion and drives appetite regulation, so you feel full sooner
- Glucagon raises how much energy your body burns
Semaglutide works on one of those. Tirzepatide works on two.
Retatrutide's triple agonist action distinguishes it from other GLP-1 medications, and that third receptor is why researchers expected stronger results. It also explains the slow climb, since three pathways activating at once takes more adjusting than one.
For a wider look at how these compounds sort into groups, see our guide to the different types of peptides.
Retatrutide Dosage Chart
There is no official retatrutide dosage yet because the medication is still under FDA review. What we do have is the Phase 3 protocol, and trial doses have ranged from 1 mg to 12 mg once weekly.
Here is the schedule for someone heading to the maximum dose.
| Timeline | Weekly dose | What it is |
|---|---|---|
| Weeks 1 to 4 | 2 mg | Starting dose, same for everyone |
| Weeks 5 to 8 | 4 mg | Step up, or your target if assigned 4 mg |
| Weeks 9 to 12 | 6 mg | Step up only, never a target dose |
| Weeks 13 to 16 | 9 mg | Step up, or your target if assigned 9 mg |
| Week 17 onward | 12 mg | Maximum dose and final target |
Not everyone climbs the whole ladder. Your assigned target decides where you stop.
- The 4 mg target takes one step and about 5 weeks
- The 9 mg target takes three steps and about 16 weeks
- The 12 mg target takes four steps and about 20 weeks
The 6 mg dose was never tested as a destination. It softens the jump between 4 mg and 9 mg, so any chart listing it as a maintenance dose is describing something the trials never studied.
Each dose was given as a subcutaneous injection on the same day each week, rotating injection sites.
Two things to keep in mind. Some Phase 3 results have been announced by Lilly but not yet published in a peer-reviewed journal, and research is still running. The final schedule could look different once the FDA reviews the complete data.
Why Does the Starting Dose Begin at 2 mg?
The low start was tested directly rather than assumed.
The Phase 2 trial published in the New England Journal of Medicine split its 4 mg and 8 mg groups in two. Some participants entered at 2 mg and others at 4 mg, both climbing to the same target.
Researchers reported that stomach effects were dose-related, mostly mild to moderate, and partially reduced by the 2 mg start.
Weight loss was reported for each target group as a whole, with both entry points pooled together, so the paper does not separate results by starting dose. What it does show is that the lower entry point made the early weeks easier to get through.
Phase 3 took that finding and applied it to everyone. All participants now begin at 2 mg regardless of target, with four weeks between each step so your body has time to adjust before the next increase arrives.
How Much Weight Did Each Dose Deliver?
TRIUMPH-1 followed 2,339 adults for 80 weeks, starting from an average body weight of 248.5 pounds.
The 12 mg group lost 28.3% of their body weight, about 70 pounds. The 9 mg group lost 25.9%, the 4 mg group lost 19%, and placebo came in at 2.2%.
Nearly half the 12 mg group, 45.3%, lost at least 30% of their starting weight. And 65.3% of participants taking retatrutide 12 mg achieved a BMI <30 by week 80.
A smaller group kept going. The TRIUMPH-1 results show 532 people with a BMI of 35 or higher continued to 104 weeks, and those on 12 mg lost an average of 85 pounds, or 30.3%. That group started heavier, averaging 268.3 pounds, so the percentage matters more than the raw number here.
One detail most coverage skips. Lilly reported two versions of these figures.
- The numbers above assume people stayed on treatment
- Counting everyone regardless of whether they continued, the 12 mg result was 25.0%
Both are real. The second is closer to what happens outside a trial.
The 4 mg Dose Is the One People Overlook
Most coverage treats 12 mg as the finish line. The 4 mg data argues otherwise.
That group reached 19% average weight loss, about 47 pounds, after a single dose increase. They got there by week 5 instead of week 20.
The tolerability numbers are the surprising part. In TRIUMPH-1, 4.1% of the 4 mg group stopped treatment because of side effects, compared with 4.9% of the placebo group.
People on 4 mg quit less often than people taking nothing at all.
That is the real trade the chart offers. A dose you can stay on supports long term success better than a higher one you abandon in month four.
Retatrutide Results Across the Other Trials
TRIUMPH-1 was not the only Phase 3 study. Four more have reported, each testing the same ladder in a different group of people.
- TRIUMPH-2 enrolled adults with obesity and type 2 diabetes, a group that typically finds weight loss harder. The 12 mg dose produced 20.8% weight loss, about 50 pounds, with A1C down 1.6%.
- TRIUMPH-3 enrolled adults with severe obesity and existing heart disease. The 12 mg dose produced 22.6% weight loss at 80 weeks.
- TRIUMPH-4 enrolled adults with obesity and knee osteoarthritis pain, reaching 28.7% weight loss at 68 weeks.
- TRANSCEND-T2D-1 enrolled adults with type 2 diabetes, reaching 16.8% weight loss with A1C down 2.0%.
The heart disease group saw changes beyond the scale. In TRIUMPH-3, the highest dose lowered triglycerides by 37.0%, dropped systolic blood pressure by 9.3 mmHg, and took 7.5 inches off waist circumference.
That is five positive Phase 3 trials counting TRIUMPH-1, all built on the same escalation schedule. Getting the same pattern across different populations is why this chart holds up better than the versions circulating online.
Side Effects by Dose
Stomach symptoms were the most common issue, and they rose alongside dose in both trial phases.
Phase 2 rates ran higher. Nausea sat near 14% at the lowest dose, ranged from 18% to 36% at 4 mg depending on where people started, and reached up to 60% at 12 mg. Diarrhea affected about 20% of the 4 mg group.
Phase 3 came in lower across the board, likely because the added 6 mg rung smoothed the climb.
| Side effect | 4 mg | 9 mg | 12 mg | Placebo |
|---|---|---|---|---|
| Nausea | 28.6% | 38.4% | 42.4% | 14.8% |
| Diarrhea | 25.2% | 34.1% | 32.0% | 13.5% |
| Constipation | 23.8% | 25.9% | 26.1% | 10.9% |
| Vomiting | 10.6% | 22.8% | 25.3% | 4.8% |
| Stopped treatment | 4.1% | 6.9% | 11.3% | 4.9% |
Most of this happened during escalation rather than later, and eased once people settled at their maintenance dose. Our overview of peptide safety research covers how these patterns compare across the wider category.
What Would Change Someone's Dose?
Trial participants followed a set path, but study doctors could slow it down or lower it. A few things would shape that in practice.
- How your body adjusts to the current dose. Ongoing nausea usually means holding steady rather than climbing.
- Your health history. Kidney and liver function were tracked throughout the trials.
- Other medications you take. Anything affecting digestion or blood sugar would need review.
- How fast you are losing. Rapid weight loss is not automatically better, and some participants had doses reduced after losing enough.
None of this is something to work out alone. Any real plan would need medical guidance from a licensed provider.
Where Retatrutide Stands with the FDA
Retatrutide is an investigational drug available only through clinical trials right now. There is no prescribing label, which is why no official dosing chart exists.
That is moving. Lilly has five positive Phase 3 trials in hand and plans to submit a Biologics License Application to the FDA in Q1 2027. A standard review takes about ten months, so a decision would follow after that.
The bigger picture is encouraging. Retatrutide sits in the same family as the peptides for weight loss already in pharmacies, with the strongest late-stage results published so far.
What the Chart Does Not Cover
The trial protocols answer a lot. Three things they do not.
- There is no missed dose rule. Approved drugs print that on the label. Advice you find online is copied from other weekly injections, which are different medications with different half-lives.
- Milligrams are not syringe units. Trial protocols list doses in mg, but that number depends on your vial size and how much bacteriostatic water goes in. Our peptide dosage calculator has retatrutide built in and converts a target dose into syringe units for you.
- The schedule could still shift. A Phase 3b trial comparing different escalation schemes is underway right now, running about 113 weeks. Its whole purpose is finding which titration approach works best, so the final chart may not match the current one.
Bottom Line
The real chart is simpler than the search results suggest. Start at 2 mg, step up every four weeks, stop at whichever target you were assigned.
12 mg produced about 28% average weight loss. 9 mg reached 25.9%. And 4 mg delivered 19% while being easier to stay on than placebo, which is the number most charts skip past.
Every target dose produced meaningful weight loss, driven by decreased appetite and a higher rate of energy burn. That is why the lowest one still matters.
More is not automatically better, and the trials were built to show it.
You cannot get retatrutide outside a study today. But the research behind this schedule is unusually strong for a compound still under review, and an FDA filing is planned for early 2027.
Disclaimer: This article is for general information only and is not medical advice. Retatrutide is still moving through FDA review, and the doses above come from clinical trial protocols rather than an approved prescribing label. Talk with a licensed healthcare professional before starting any peptide or changing your treatment plan.
