Retatrutide dosage: the doses trials tested, and why none is approved

There is no approved retatrutide dosage. Retatrutide is not approved by the FDA or any other regulator, and it is not on the market [Lilly, Oct 2026]. An approved dose only exists once a regulator reviews the evidence and prints it on a drug label. What does exist is a record of the doses Lilly's trials tested, how those trials raised the dose and what happened at each level.

That record is what this page reports, as facts about the trials. It is not a dosing guide, and nothing here tells anyone what to take. Every figure carries its source, with the source type labeled.

Is there an approved retatrutide dosage?

No. In trials, retatrutide is taken as a once-weekly subcutaneous injection, which means a shot under the skin [Lilly, Oct 2026]. The dose each volunteer received was set by the trial's protocol and assigned at random. In the TRIUMPH-2 trial, volunteers gave themselves the weekly injections [Lancet, Sep 29, 2026].

So a "retatrutide dosage chart" can only be a chart of what researchers tested. It can't tell anyone outside a trial what a safe or useful dose would be.

What doses did the trials test?

Here is every trial with published or announced results, with the doses it tested. All doses were given once a week by injection under the skin. This table records what each trial tested. It is not a dosage chart.

The phase 2 sources we could read list each arm's steps but not how many weeks each step lasted [ClinicalTrials.gov, NCT04881760]. The phase 2 diabetes authors wrote that those results informed dose selection for the phase 3 programme [Lancet, 2023].

Retatrutide dosing schedule: how phase 3 stepped the dose up

The phase 3 trials all used the same pattern. Lilly describes it this way: The TRIUMPH clinical trial program includes five doses of retatrutide: 2 mg, 4 mg, 6 mg, 9 mg and 12 mg. It adds that volunteers began on 2 mg once weekly and increased the dose every four weeks until reaching their target dose [Lilly, Dec 11, 2025].

In TRIUMPH-1, Lilly spelled out each path. The 4 mg group got there via one step at 2 mg. The 9 mg group went via steps at 2 mg, 4 mg and 6 mg. The 12 mg group went via steps at 2 mg, 4 mg, 6 mg and 9 mg [Lilly, May 21, 2026]. The trial design paper describes the 80-week trials as 16 weeks of dose escalation followed by 64 weeks at the assigned dose [DOM, Oct 15, 2025].

Three more details matter for reading the results:

• Blinding. Doses were reached through a fixed dose escalation regimen, and neither volunteers nor staff knew who got which dose [DOM, Oct 15, 2025].
• Dose cuts were allowed. A permanent reduction was permitted for management of gastrointestinal adverse events or inadequate oral intake that other steps hadn't fixed. It was also allowed for people who reached a BMI of 22 or lower, or felt they had lost too much weight [DOM, Oct 15, 2025].
• Some trials aimed for the most each person could tolerate. The TRIUMPH-1 extension used a maximum tolerated dose of 9 mg or 12 mg [Lilly, May 21, 2026]. The 10,000-person outcomes trial gives escalated doses up to a maximum tolerated dose [ClinicalTrials.gov, NCT06383390].

What about "retatrutide dosage per week"? In every trial above, the dose a group was assigned was given as one injection a week.

Why did the trials raise the dose in steps?

The trial design paper gives the reason in one sentence. The doses and the escalation were selected based on safety and efficacy data as well as exposure‐response modelling from phase 1 and 2 retatrutide studies [DOM, Oct 15, 2025]. Exposure-response modelling means estimating how the amount of drug in the blood relates to its effects and side effects. The phase 2 starting-dose results in the next section are part of that evidence.

The once-a-week rhythm also comes from early work. In the 12-week phase 1b study, the drug's half-life was about 6 days. In other words, the level in the blood fell by half roughly every six days. The authors wrote that its pharmacokinetics suggest suitability for once-weekly dosing [Lancet, 2022]. How the drug acts on its three receptors is explained in how retatrutide works.

What happened when trials started lower?

The phase 2 obesity trial is the one that tested starting doses directly. Some groups began at 2 mg, others at 4 mg. The paper found that the gut side effects were partially mitigated with a lower starting dose (2 mg vs. 4 mg) [NEJM, 2023].

The registry's posted counts show the size of the difference. For the 8 mg groups, nausea affected 60.0% of people whose first dose was 4 mg, against 17.1% of those whose first dose was 2 mg. Vomiting affected 25.7% against 5.7%. For 4 mg, nausea affected 36.4% without a step-up and 18.2% with one [ClinicalTrials.gov, NCT04881760]. On placebo, it was 11.4%. Each group held only about 35 people, so these numbers are rough.

The phase 2 diabetes trial pointed the same way. Gut side effects ranged from 13% on 0.5 mg up to 50% in the 8 mg fast escalation group [Lancet, 2023]. In phase 3, Lilly said the most common gut side effects in TRANSCEND-T2D-1 occurred primarily during dose escalation [Lilly, Mar 19, 2026]. The full side-effect picture is in retatrutide side effects.

Did higher doses lose more weight?

Yes, but with more dropouts. In TRIUMPH-1's peer-reviewed paper, average weight change over 80 weeks was −17.6% on 4 mg, −23.7% on 9 mg and −25.0% on 12 mg. On placebo it was −3.9% [NEJM, Sep 29, 2026]. Those figures count everyone assigned to each dose, including people who stopped.

Dropouts rose the other way. Side effects led 4.1% of people on 4 mg to stop, 6.9% on 9 mg and 11.3% on 12 mg, against 4.9% on placebo [Lilly, May 21, 2026]. Lilly pointed out that the 4 mg dose was reached with only a single escalation step and had a lower dropout rate than placebo [Lilly, May 21, 2026]. The pattern isn't always tidy. In TRIUMPH-2, more people stopped on 9 mg (12%) than on 12 mg (8%) [Lancet, Sep 29, 2026]. Trial-by-trial weight results are in retatrutide weight loss results.

What is the retatrutide max dose?

The highest dose tested in any trial that has reported is 12 mg once a week [NEJM, Sep 29, 2026] [Lilly, Dec 11, 2025]. That is the top of what researchers chose to test. It is not a proven safe maximum, and no regulator has set one. Some volunteers on 12 mg stopped the drug because of side effects, as the dropout figures above show.

Why there's no retatrutide dosage chart, calculator or units guide here

People who search for a dosage chart, a "starting dose" or syringe units are usually looking at a vial bought online. Those products are not Lilly's trial drug, and no one has checked what is inside them. The FDA says sellers have labeled retatrutide "for research purposes" while selling it directly to consumers for human use with dosing instructions [FDA, Oct 1, 2026]. Retatrutide also cannot be used in compounding under federal law, so no pharmacy can legally prepare it [FDA, Oct 1, 2026].

What's on a vial's label may not match what's in it. The TGA, Australia's regulator, tested one vial sold as retatrutide. It found undeclared semaglutide and no retatrutide, at about 8 times the level in approved semaglutide products [TGA, Sep 14, 2026]. The buyer had been hospitalized after uncontrollable vomiting. In Victoria, Australia, health officials have linked six cases of acute liver injury to products labeled retatrutide [Victoria Health, Jun 19, 2026]. A dose worked out from a label like that has nothing to stand on.

Measuring is a hazard of its own. With compounded semaglutide, the FDA has logged patients who administered five to 20 times more than the intended dose. It cited confusion between different units of measurement (e.g., milliliters, milligrams and “units”). Some of those patients needed hospital care [FDA, Jul 26, 2024]. That's why this site gives no conversions, no mixing steps and no calculators. What the online listings are, and why selling them is illegal, is covered in retatrutide for sale.

When will there be a real retatrutide dosage label?

A label would settle the questions trials leave open: the starting dose, the steps, the maintenance doses and the maximum. Approved drugs show what that looks like. The Zepbound label, for example, sets a starting dose for treatment initiation, three maintenance doses and a Maximum Recommended Dosage of 15 mg once weekly [FDA label, Aug 2026]. The FDA approved those numbers after reviewing Lilly's evidence.

For retatrutide, that review hasn't begun. Lilly says it plans to submit its application to the FDA in Q1 2027 [Lilly, Sep 29, 2026]. A decision would follow the FDA's review, so no label can exist before then. Lilly also hasn't said which doses it will ask for. Two running trials could shape the answer. TRIUMPH-9 is comparing Different Retatrutide Dose Escalation Schemes, with main results estimated for October 2028 [ClinicalTrials.gov, NCT07357415]. TRIUMPH-6 is testing what keeps weight off after 80 weeks: staying on the same dose, changing the dose or switching to placebo. Its main results are estimated for April 2028 [ClinicalTrials.gov, NCT06859268].

The timeline is covered in retatrutide FDA approval. For the basics of the drug, start with what is retatrutide.