Retatrutide Dosing Schedule and Titration Protocol

The retatrutide dosing schedule used in Lilly's Phase 3 TRIUMPH trials starts at 2 mg once a week and steps up every 4 weeks, through 4, 6 and 9 mg, until each person reaches a target of 4, 9 or 12 mg. On that ramp the first 12 mg dose lands at week 17. It's the only retatrutide schedule that has been tested in thousands of people.

As of September 2026, retatrutide is still in Phase 3 trials and no approved version exists yet. Lilly said in July 2026 that it plans to file for US approval (a Biologics License Application) in the first quarter of 2027. Until then there's no label, no official titration table and no missed-dose rule, so where retatrutide has no answer, this page uses the tirzepatide and semaglutide labels and says so.

The retatrutide dosing schedule in Phase 3 trials

Every TRIUMPH result Lilly has released uses the same ramp. In the TRIUMPH-2 and TRIUMPH-3 results from July 2026, Lilly describes people starting at 2 mg once weekly and increasing "in a stepwise approach every four weeks" until they reached their target: 4 mg after one step at 2 mg, 9 mg via steps at 2, 4 and 6 mg, and 12 mg via steps at 2, 4, 6 and 9 mg. TRIUMPH-4 (December 2025) and TRIUMPH-1 (May 2026) describe the same 2 mg start and 4-week steps.

Laid out by week, that looks like this. The week numbers are our arithmetic from the 4-week steps; Lilly's releases give the steps and the interval.

One detail changes how you read this. In the trials, the target was assigned at random on day one. People didn't choose when to step up or where to stop, and nobody moved to 12 mg because 9 mg had stalled. Every dose was one injection under the skin, once a week, for 68 weeks in TRIUMPH-4 and 80 weeks in TRIUMPH-1, TRIUMPH-2 and TRIUMPH-3. If you want the same steps converted into syringe units for a given vial, the retatrutide dosage chart does that.

How much retatrutide the schedule adds up to

People ask "how much reta for a cycle" because vials come in fixed sizes. Adding up the trial ramp gives a straight answer, and one surprise: the 9 mg and 12 mg paths use exactly the same amount through week 16.

These are sums of the published steps, not a dosing plan. For your own numbers, including how many doses a given vial holds at each step, the retatrutide calculator does the math.

Why the dose goes up every 4 weeks

Two things set the pace: how long retatrutide stays in your body, and how your stomach handles each jump.

In the Phase 1b trial published in The Lancet in 2022, retatrutide's half-life was about 6 days, and the authors said that suits once-weekly dosing. A drug that lingers that long builds up over several weekly shots before levels settle. The Zepbound label says tirzepatide, with a half-life of about 5 to 6 days, reaches steady blood levels after 4 weeks of weekly doses. That's tirzepatide data, not retatrutide.

Our read: with a half-life of about 6 days, 4 weeks is between 4 and 5 half-lives, enough for each dose to get close to its full level before the next increase. That way each step is judged near full strength.

As for why increase the reta dose at all: in TRIUMPH-1, a higher target meant more weight loss and more side effects.

The gap between 9 mg and 12 mg is 2.4 percentage points of body weight. The gap in people who quit over side effects is 4.4 points.

Why the ramp starts at 2 mg, not 4 mg

The Phase 2 obesity trial, published in the New England Journal of Medicine in 2023, tested this directly. It gave 338 adults retatrutide or placebo for 48 weeks, and two of the target doses were reached from different starting points. The authors reported that stomach side effects were dose-related and "partially mitigated with a lower starting dose (2 mg vs. 4 mg)."

The results posted on ClinicalTrials.gov show how big that difference was. At the 8 mg target, 21 of 35 people who started at 4 mg had nausea (60.0%), against 6 of 35 who started at 2 mg (17.1%). At the 4 mg target it was 12 of 33 (36.4%) against 6 of 33 (18.2%). A parallel Phase 2 trial in type 2 diabetes, in The Lancet, pointed the same way: its highest rate of stomach side effects, 12 of 24 people (50%), was in the fast 8 mg group, the one that started at 4 mg.

Phase 3 went slower still. The Phase 2 12 mg group climbed 2, 4, 8, then 12 mg. The Phase 3 12 mg path adds a 6 mg step and uses 9 mg in place of 8 mg, so no single jump is bigger than 3 mg. If you're weighing whether to begin lower than 2 mg, the retatrutide starting dose page covers lower starting points, including the 1 mg group in the Phase 2 obesity trial.

When to hold a step instead of going up

The trials ran on a fixed calendar because they had to compare doses fairly. Approved drugs in the same class give prescribers room to slow down. The Wegovy label says that if a dose isn't tolerated during the climb, consider delaying the next increase by 4 weeks. The Zepbound label says to stay at least 4 weeks on each dose and to consider a lower maintenance dose if the current one isn't tolerated. That's semaglutide and tirzepatide guidance, not retatrutide's, but it's the closest thing to a rulebook.

Threads asking whether they're going up too fast come up again and again in retatrutide communities on Reddit, often from someone about to step up while still feeling sick from the last increase. Those are user reports, not evidence, but they match the trial pattern: side effects bunch up after each increase.

TRIUMPH-4 shows what pushing to the top can cost. In 445 adults with excess weight and knee osteoarthritis, 12.2% on 9 mg and 18.2% on 12 mg stopped over side effects, against 4.0% on placebo, and Lilly noted some of those stops were for "perceived excessive weight loss."

Our read: 4 mg is a trial dose in its own right. In TRIUMPH-1 it averaged 19.0% weight loss, and fewer people stopped over side effects on 4 mg (4.1%) than on placebo (4.9%), so stopping there still puts you on a dose the trials tested. Ask your doctor about it if the higher steps are wearing you down. The full list of what to expect is on the retatrutide side effects page.

Can you dose reta twice a week?

Nobody has tested it. Every retatrutide trial so far, from Phase 1b through Phase 3, used one injection a week. People on Reddit describe splitting the weekly dose into two or three smaller shots, hoping for fewer peaks in nausea, and other threads argue against it. Neither side has data. No trial has measured whether splitting changes side effects, weight loss or blood levels.

The Zepbound label allows moving your injection day as long as the two doses are at least 3 days (72 hours) apart. That's about shifting a day, not splitting a dose, and it's tirzepatide guidance. Splitting also doubles the number of times you draw a small volume from a vial, and each draw is another chance to misread the syringe. The microdosing retatrutide page covers what's known about smaller, more frequent doses.

The vial matters as much as the schedule. Nothing sold online is Lilly's product, and Lilly says retatrutide "cannot be legally sold or marketed for human use." If you're looking at retatrutide for sale, a batch-specific third-party test showing the actual amount in the vial matters more for your dose math than any week-by-week table, because every step above assumes the vial holds what its label says.

Missed doses and restarting after a break

There's no retatrutide missed-dose rule, because there's no retatrutide label. The two labels closest to it disagree a little:

• Zepbound (tirzepatide): take the missed dose within 4 days (96 hours). If more than 4 days have passed, skip it and take the next dose on your usual day.
• Wegovy (semaglutide): take it as soon as you can if your next dose is more than 2 days away; skip it if it's less than 2 days away. If you miss 2 or more doses in a row, restart the climb at a lower dose to reduce stomach side effects.

Retatrutide's half-life (about 6 days) is close to tirzepatide's (about 5 to 6 days on the Zepbound label), but nobody has tested whether the same windows apply. The Wegovy rule is the one to raise with your doctor after a break of 2 weeks or more. Going straight back to 12 mg after a gap means restarting at your highest dose with none of the gradual build-up the trials used.

Should you cycle retatrutide?

No retatrutide trial has used cycles, planned breaks or a taper. In the obesity trials, treatment ran without pauses: 48 weeks in Phase 2, 68 to 80 weeks in Phase 3, and 104 weeks in the TRIUMPH-1 extension, where people with a BMI of 35 or more who stayed on 12 mg averaged 30.3% weight loss. The "8 weeks on, 8 weeks off" retatrutide cycle posted on peptide sites has no study behind it.

The closest data on stopping comes from tirzepatide. In SURMOUNT-4, published in JAMA in 2024, 670 adults had lost an average of 20.9% after 36 weeks on tirzepatide. Half then switched to placebo, and their weight went back up by 14.0% over the next 52 weeks, while those who stayed on tirzepatide lost a further 5.5%. That's tirzepatide data, not retatrutide, and no one has published what happens when people stop retatrutide or step down slowly.

So the honest answer on retatrutide cycle length is that the only lengths tested are the trial durations, all of them continuous. If you're weighing a break or a stop, the how long can you take retatrutide page covers the longest data, and it helps to agree with your doctor beforehand how you'll track your weight and blood pressure once the weekly doses end.