Retatrutide Tracker: What Is Known and What a Log Can Hold

What is retatrutide?

Retatrutide, also called LY3437943, is an experimental drug from Eli Lilly that activates three receptors at once: the glucose-dependent insulinotropic polypeptide receptor, the glucagon-like peptide-1 receptor and the glucagon receptor.^[1] Because it acts on three targets, it is called a triple agonist. LY3437943 is the code name used in the early papers.^[2] It is given as a once-weekly injection under the skin in clinical trials.^[1] Eli Lilly describes it as investigational, which means no regulator has approved it for any use.^[3] It is being studied for obesity and related conditions, and the table below gives the status as of October 2026. Because it has no approved product, there is no prescribing information to quote, and nothing on this page is guidance on how anyone should use it. Dose decisions in a trial belong to the trial clinicians.

Developer

Eli Lilly and Company.^[3]

Mechanism

Agonist of the GIP, GLP-1 and glucagon receptors.^[1]

FDA status

Investigational. Not approved as of October 2026.^[3]

Latest trial stage

Phase 3. Results from the TRIUMPH-2 and TRIUMPH-3 trials were announced on July 23, 2026.^[3]

Compounding status

Cannot be used in compounding under federal law, per the FDA.^[4]

Half-life source

About 6 days in a phase 1b study.^[2]

Is retatrutide FDA-approved?

No. As of October 2026 retatrutide has not been approved by the FDA, and no retatrutide product has an FDA label. In its July 23, 2026 announcement of phase 3 results, Eli Lilly called the drug investigational and said it plans to submit a Biologics License Application to the FDA in the first quarter of 2027.^[3] A submission is a request for review, not an approval, and the announcement does not say when or whether a decision will come, so nothing here predicts a date. Until a label exists, any schedule you see online for retatrutide did not come from a regulator. That is why PepTrac gives no dose or schedule for it. A tracker can still keep dated records for trial participants and for anyone logging for a clinician. We will update this page when the status changes, and the date at the top shows when it last did.

Can retatrutide be legally compounded?

According to the FDA, no. The agency's page on unapproved GLP-1 drugs, dated October 1, 2026, states that retatrutide and cagrilintide cannot be used in compounding under federal law.^[4] The same page lists safety problems with unapproved and compounded GLP-1 products, including reports of dosing errors and adverse events, and says that a multiple-dose vial should be discarded within 28 days after first use. It counted 990 adverse event reports for compounded semaglutide and more than 730 for compounded tirzepatide as of May 31, 2026.^[4] Compounding is a separate question from approval, and for retatrutide the FDA's answer is that federal law does not allow it. PepTrac does not sell, source or supply retatrutide or any other medication, and it does not tell anyone where to find it. Questions about where a product comes from belong with a licensed clinician or pharmacist.

What did the phase 2 retatrutide trial test?

The phase 2 trial, published in the New England Journal of Medicine in 2023, enrolled 338 adults with obesity or overweight plus a weight-related condition. They received weekly retatrutide at 1, 4, 8 or 12 mg, or placebo, for 48 weeks, and the main measure was weight change at 24 weeks.^[1] At 48 weeks the mean weight change was 8.7 percent at 1 mg, 17.1 percent in the combined 4 mg groups, 22.8 percent at 8 mg and 24.2 percent at 12 mg, against 2.1 percent on placebo.^[1] Gastrointestinal events were the most common side effect, rose with dose, and eased with a lower starting dose of 2 mg rather than 4 mg. Heart rate rose with dose, peaked at 24 weeks and then declined.^[1] These are trial facts for a group of volunteers, not guidance, and Eli Lilly funded the study.

What did the phase 3 TRIUMPH trials report?

Eli Lilly announced results from two more phase 3 trials on July 23, 2026. In TRIUMPH-2, which enrolled adults with obesity or overweight and type 2 diabetes, the highest dose group lost an average of 20.8 percent of body weight at 80 weeks. In TRIUMPH-3, which enrolled adults with severe obesity and established cardiovascular disease, participants lost up to an average of 22.6 percent at 80 weeks.^[3] Eli Lilly reported positive results from five phase 3 studies in its TRIUMPH program, and the figures quoted here are the top averages it reports.^[3] These figures come from a company press release, not from a peer-reviewed paper, so treat them as early and read the full publications when they appear. Trial averages describe groups, and they do not predict what any one person will experience or whether an approval will follow.

What is retatrutide's half-life?

About 6 days, based on a phase 1b trial of LY3437943 in 72 adults with type 2 diabetes, who received once-weekly injections of retatrutide, placebo or dulaglutide for 12 weeks. The authors reported that its pharmacokinetics were dose proportional and that its half-life was approximately 6 days, which they said suggests suitability for once-weekly dosing.^[2] Eli Lilly funded the study. A half-life of about 6 days means that roughly half of a dose remains after 6 days and a quarter after 12, so one dose keeps acting for weeks. PepTrac uses 144 hours, or 6 days, as the half-life in its catalog and 24 hours as the time to peak. This is early-phase data from a small study, so treat any curve built on it as a rough guide. For the decay arithmetic, see retatrutide half-life.

What does PepTrac's estimate look like for a weekly retatrutide entry?

Take 1 mg as an arithmetic input, which is the lowest dose group in the phase 2 trial.^[1] After one entry, PepTrac's model reads 0.52 on day 7, with a range of 0.42 to 0.59. After four weekly entries, the level just before the fifth reads 0.90, with a range of 0.65 to 1.13. These are relative units scaled so each entry peaks at its own milligrams, and they are not blood concentrations. The range comes from re-running the model with the half-life and time to peak each changed by 20 percent, so it shows sensitivity to those two inputs, not statistical confidence. Because the half-life comes from a phase 1b study, treat the range as a floor on the uncertainty, not a ceiling. The amount is an arithmetic example, not a dose recommendation, and the curve is not a lab result.

What can a retatrutide log hold?

A log can hold only what a person enters, and for a drug with no label that is the whole point of keeping it tidy. For a trial participant, or anyone keeping records to show a clinician, the useful fields are the date and time, the amount in milligrams, the injection site and body weight. PepTrac stores each of those and shows the level estimate described above. It gives no schedule, no dose steps and no suggestion for retatrutide, and it does not prescribe or supply it. PepTrac also lacks a dedicated side-effect screen, so keep symptoms elsewhere. If you are in a trial, follow the trial team's instructions and ask whether they want you to keep your own log. The GLP-1 tracker page covers the approved medicines, and their labels, in one table.