Retatrutide Tracker: What It Is & What to Track (2026)

01

What is retatrutide?

Retatrutide (research code LY3437943) is an experimental, once-weekly injectable from Eli Lilly. What sets it apart is that it is a triple hormone-receptor agonist — it activates three receptors at once: GIP, GLP-1, and glucagon (Jastreboff et al., NEJM 2023).

For comparison, semaglutide (Ozempic, Wegovy) is a single GLP-1 agonist, and tirzepatide (Mounjaro, Zepbound) is a dual GIP/GLP-1 agonist.

The added glucagon action is the "third G," and it is thought to raise energy expenditure and act on liver fat — while also being the reason some trial-specific effects (like a modest rise in heart rate) matter for tracking.

To be clear about entities: retatrutide is not tirzepatide and not semaglutide. It is a distinct, later-stage molecule.

If you are comparing the approved options instead, see our semaglutide vs. tirzepatide guide.

02

Is retatrutide FDA-approved? Current status (2026)

No. As of 2026, retatrutide is investigational and not approved by the FDA — or any major regulator — for any use. It is available only to people enrolled in clinical trials.

Eli Lilly has said it anticipates regulatory submission around 2026 following its pivotal Phase 3 readouts, which means the earliest realistic public availability would be roughly 2027–2028, and only if trials and review succeed (Eli Lilly).

Because there is no approved label, there is no official dosing schedule for the public, no pharmacy supply, and no companion app — anyone selling "retatrutide" outside a trial is not offering an approved product.

03

Retatrutide trial results so far

Here is where the excitement comes from.

The headline data below is a snapshot of published and topline trial results — treat it as evidence, not a promise, since averages hide big individual variation and Phase 3 details are still being published.

Sources: NEJM Phase 2; TRIUMPH-1 (ClinicalTrials.gov NCT05929066); AJMC — TRIUMPH-1 topline; Eli Lilly investor — Phase 3 T2D.

In the Phase 2 obesity trial, the 12-mg dose produced a mean 24.2% weight reduction at 48 weeks, with a clear dose-response (roughly 8.7% at 1 mg up to 24.2% at 12 mg) (NEJM 2023).

Trial participants started at a low dose (2 mg) and escalated every four weeks — the same titrate-slowly logic used by approved GLP-1s.

A separate Phase 2a trial reported large reductions in liver fat in people with metabolic dysfunction-associated steatotic liver disease (Nature Medicine 2024).

These numbers are why retatrutide is discussed as potentially best-in-class — but they come from controlled trials, not real-world use.

In Lilly's Phase 3 TRIUMPH-1 topline results (May 2026), people on 12 mg lost an average of 28.3% of body weight at 80 weeks; in a pre-specified extension in people with a BMI of 35 or more, those who stayed on 12 mg reached 30.3% at 104 weeks.

These are company-reported figures; full peer-reviewed data are pending, and retatrutide is not approved anywhere.

04

What tracking retatrutide would look like

Even though you can't be prescribed retatrutide, the tracking framework is worth understanding — it's the same discipline that helps on any GLP-1, and it's exactly what trial participants are asked to monitor.

A triple agonist adds one wrinkle: because the glucagon component nudged heart rate up in trials, resting heart rate becomes a data point worth watching alongside the usual set (NEJM 2023).

Side effects seen in trials — what the data shows

In the Phase 3 TRIUMPH-1 obesity trial (topline, May 2026), the most common adverse events were gastrointestinal.

At 12 mg in TRIUMPH-1: nausea 42.4%, diarrhea 32.0%, constipation 26.1%, vomiting 25.3%; 11.3% stopped because of side effects (vs 4.9% on placebo); altered skin sensations (dysesthesia) were also reported (AJMC — TRIUMPH-1).

In the Phase 2 trial, GI effects were mostly mild-to-moderate, dose-related, and eased by a lower starting dose (NEJM 2023).

Trials also tracked the modest heart-rate increase noted above.

For how GI side effects compare across the approved GLP-1 class, see our guide to GLP-1 side effects.

Retatrutide is investigational, so the points below come from the labels of approved GLP-1 medicines; if you are in a trial, follow your study team.

Safety basics for any GLP-1 log. Don't use these medicines if you or a close relative has had medullary thyroid cancer, or if you have MEN 2.

They are not used during pregnancy — tell your prescriber right away if you become pregnant or plan to, because some must be stopped weeks to months beforehand.

If you also take insulin or a sulfonylurea, watch for low blood sugar (shakiness, sweating, confusion).

Vomiting or diarrhea that keeps you from holding down fluids can dehydrate you and strain your kidneys — call your clinician.

A tracker organizes your records; the package leaflet in your country and your prescriber come first.

05

How to build a metabolic-tracking routine now

You don't need retatrutide to build the habit that makes any GLP-1 work — and starting now means you arrive prepared if a triple agonist ever reaches the market.

This takes under two minutes a week.

1. 1

   Weigh in on fixed days.

   Pick 1–3 mornings, same conditions, and read the trend, not the daily noise.

2. 2

   Track protein daily.

   Muscle protection is the single most under-rated habit in any rapid-weight-loss journey.

3. 3

   Log resistance-training sessions.

   Strength work is the strongest defense against losing lean mass.

4. 4

   Note how you feel.

   Appetite, energy, GI comfort, and — if relevant — resting heart rate.

5. 5

   Photo every 2–4 weeks.

   Same lighting and angle; body-composition change is often invisible on the scale.

6. 6

   If you enter a trial, log the dose and site right after each injection and bring the record to every study visit.

06

Do you need an app for this?

Right now, "tracking retatrutide" mostly means staying informed and building the underlying habits — no approved product means no dedicated companion app. A notebook is fine.

What a general wellness app adds is the automation people forget: a weight trend that smooths daily noise, daily protein and movement logging, and a place to note symptoms or resting heart rate over time.

If you want those habits living in one place — ready for whatever GLP-1 you and a doctor eventually choose — a wellness app like HAVIT is a natural home.

Compare options in our best GLP-1 tracker apps guide and pick what you'll actually keep using; consistency beats hype.

07

Related guides

• Semaglutide vs. tirzepatide: which GLP-1 is right for you?
• Wegovy tracker: what to log on Wegovy and how
• GLP-1 side effects: nausea, GI symptoms & red flags
• The complete GLP-1 tracker app guide

08

Why HAVIT — Medication + Behavior Change, in One App

GLP-1 medications can meaningfully reduce weight — but the number on the scale is only part of the story.

The lean-mass share of the weight lost on GLP-1 therapy has ranged from 40–60% in some trials to 15% or less in others — and lean mass counts organs, bone and fluid, not only muscle (Neeland et al., Diabetes, Obesity and Metabolism, 2024), and results tend to fade once the medication stops unless new habits take their place.

That's why leading guidance treats medication as one part of care, not the whole: the U.S. Preventive Services Task Force recommends that adults with obesity be offered intensive, multicomponent behavioral interventions (USPSTF, Grade B).

HAVIT is built for exactly this moment — one app that unites medication tracking, body composition, nutrition and protein, daily habit-building, and an AI coach that adapts to you.

Across our own 1,090 GLP-1 users, the most consistent trackers built the strongest habits (see the GLP-1 habit report).

Manage the medicine and the muscle — together. Start with HAVIT →

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