Retatrutide Dosage Chart (mg, Units and Weekly Schedule)

The retatrutide dosage chart used in Lilly's Phase 3 trials starts at 2 mg once a week and steps up every 4 weeks, through 4, 6 and 9 mg to a top dose of 12 mg, which takes 16 weeks to reach. People assigned to 4 mg or 9 mg stopped climbing there. As of September 2026 no approved label exists, so every chart you'll find, this one included, is built from trial data rather than prescribing rules.

Plenty of charts online mix two different trial ladders or add rungs no trial used. Every table below names the trial it came from or says it's our arithmetic, and where no trial has tested something people ask about, we say so.

The retatrutide dosage chart from the Phase 3 trials

TRIUMPH-1, an 80-week trial that randomized 2,339 adults with obesity or overweight, spells the schedule out. Everyone on retatrutide "initiated treatment with 2 mg once weekly and increased the dose in a step-wise approach every four weeks" until reaching a target of 4 mg, 9 mg or 12 mg. Lilly's releases for TRIUMPH-2, TRIUMPH-3 and TRIUMPH-4 describe the same ladder.

No Phase 3 group stayed on 6 mg; it was only ever a stepping stone. The steps also get bigger near the top: 2 mg at a time at first, then 3 mg at a time from 6 to 9 and from 9 to 12.

The last column is plain arithmetic, and it's the one people forget when they plan how long a vial lasts. By the end of week 16 on the 12 mg path, you've taken 84 mg in total. From then on, each week adds another 12 mg.

TRIUMPH-1 also ran an extension to 104 weeks for 532 people with a starting BMI of 35 or more. They got 24 more weeks of retatrutide, with a blinded step up to a "maximum tolerated dose" of 9 mg or 12 mg, so the top-dose data now runs to 104 weeks. For the week-by-week version with calendar dates, see our retatrutide dosing schedule.

What each dose did in TRIUMPH-1

More milligrams bought more weight loss, and more side effects. Lilly reported two versions of the weight numbers. The efficacy estimand shows what happened if everyone stayed on treatment; the treatment-regimen estimand counts everyone, including people who stopped.

On 12 mg, about 4 in 10 people (42.4%) had nausea at some point, against about 1 in 7 on placebo. Fewer people stopped 4 mg over side effects than stopped placebo.

Our read: 4 mg delivered about two-thirds of the 12 mg weight loss (19.0% against 28.3%) with about a third of the dropout rate over side effects (4.1% against 11.3%). 12 mg is the highest rung the trials tested, and the 4 mg groups stopped three rungs lower.

TRIUMPH-4, in 445 adults with knee osteoarthritis, tested only 9 mg and 12 mg over 68 weeks: 26.4% and 28.7% average weight loss. Stopping over side effects ran higher there, 12.2% and 18.2% against 4.0% on placebo, and Lilly said that included people who stopped for "perceived excessive weight loss." Side effects by dose get their own page in our retatrutide side effects guide.

The Phase 2 chart looked different

Many charts online show steps of 2, 4, 8 and 12 mg, and some add 10 mg. Those numbers come from, or are guessed from, the 2023 Phase 2 obesity trial in The New England Journal of Medicine, which used a different ladder. Its 338 adults got 1 mg (no steps), 4 mg, 8 mg or 12 mg for 48 weeks, and, according to the trial's liver substudy in Nature Medicine, dose increases came every 4 weeks.

The Phase 2 trial also tested the first rung. Among people heading to 8 mg, the trial's registry results show nausea in 21 of 35 who started at 4 mg, against 6 of 35 who started at 2 mg. The NEJM authors wrote that stomach side effects were "partially mitigated with a lower starting dose (2 mg vs. 4 mg)." Phase 3 then started everyone at 2 mg and swapped the 8 mg rung for 6 and 9 mg. Our retatrutide starting dose page goes further into that first step.

We found no retatrutide trial, in Phase 2 or Phase 3, that used a 10 mg dose.

Turning milligrams into syringe units

Trials count in milligrams. People drawing from a vial count in units on an insulin syringe, and the link between the two is the concentration. A U-100 syringe is marked for liquid holding 100 units per mL, the strength on Lilly's own Humulin R U-100 label, so each unit mark is 0.01 mL. The formula is short: dose in mg divided by concentration in mg per mL gives mL, and mL times 100 gives units.

Anything over 100 units won't fit in one 1 mL syringe, and a 0.5 mL syringe tops out at 50 units. That's why a "units chart" copied from someone else is risky: 20 units is 2 mg at 10 mg per mL and 1 mg at 5 mg per mL. Our retatrutide units guide covers syringe sizes, and the retatrutide calculator does the math for your own vial and water.

All of this assumes the vial holds what its label says. Lilly says retatrutide is legally available only through its clinical trials and that anything sold outside them comes "with no way to verify its safety, purity or dosing." If you're comparing retatrutide for sale, you can't know whether any milligram chart applies to a vial without a batch-specific third-party test that states the amount in it.

When the chart doesn't fit you

The trials followed a fixed calendar, but approved drugs in the same class build flexibility into their labels. That's class evidence, not retatrutide data.

• Holding a step: the Wegovy (semaglutide) label says that if a dose isn't tolerated during escalation, prescribers can consider delaying the next increase by 4 weeks.
• Stopping lower: the Zepbound (tirzepatide) label lists 5 mg, 10 mg and 15 mg as maintenance doses and says to weigh response and tolerability when choosing one.
• Missing a dose: the Zepbound label allows a missed dose within 4 days (96 hours); after that, skip it and take the next one on your usual day.
• Missing two or more: the Wegovy label says to restart escalation at a lower dose after 2 or more missed weekly doses, to cut the risk of stomach side effects.

The Zepbound ladder has the same rhythm as the retatrutide one: 2.5 mg for 4 weeks, then 2.5 mg increases after at least 4 weeks each, up to 15 mg. Retatrutide's half-life of about 6 days, measured in a Phase 1b trial in The Lancet, is why one shot a week works, and also why a missed week doesn't clear the drug overnight. Any change to your schedule belongs in a conversation with your doctor.

Doses the chart leaves out

Below 2 mg, the evidence is thin. The Phase 2 obesity trial's fixed 1 mg group lost 8.7% at 48 weeks. The Phase 2 diabetes trial in The Lancet had a 0.5 mg group that lost 3.19% at 36 weeks, against 3.00% on placebo, and the 72-person Phase 1b trial tested 0.5 mg and 1.5 mg for 12 weeks in people with type 2 diabetes. None of the published trials tested a slow ladder that starts at 0.25 mg or 0.5 mg and climbs for weight loss. People on forums describe these schedules often, but they're user reports, not trial data. More on that in our microdosing retatrutide guide.

Above 12 mg, we found nothing. The Phase 1b trial's top group reached 12 mg through 3, 6 and 9 mg steps, and none of the later trials we found went higher.

Split dosing is the other gap. Every retatrutide trial we found gave one injection a week, so twice-weekly half doses have no published data behind them. If you do split a dose, each draw needs its own units calculation, since half of 9 mg at 10 mg per mL is 45 units, not the 90 on the chart.

The schedule itself may still change. TRIUMPH-9, a Phase 3b trial of about 600 adults without type 2 diabetes, is comparing 3 different dose-escalation schemes, and its ClinicalTrials.gov record doesn't list their doses. Its primary completion date is estimated for October 2028.

As of September 2026, Lilly plans to file a biologics license application with the FDA in the first quarter of 2027. If retatrutide is approved, the first real prescribing chart, with official rules for missed doses and dose changes, will come from that label.