Investigational GIP/GLP-1/glucagon receptor triple agonist peptide

Retatrutide

aka LY3437943

Evidence grade

Moderate human evidence

for weight loss

User score everyone · n = 25

US FDA Not approved checked 2026-11-13

WADA 2026 Likely prohibited (S0) by class rule · checked 2026-11-13

EU EU clinical-trial registration found; EMA marketing authorisation not found. · checked 2026-11-13

Goals: Fat loss Compare with another peptide →

User reports

approximate — combined from two independent Reddit reads

Men 45–60

5 men aged 45–60

small sample · n = 5

Outcome mixed 2 of 5 · positive 2 of 5 · unclear 1 of 5

Benefits fat loss 4 of 5 · less appetite 2 of 5 · gut 1 of 5 · joints / tendons 1 of 5

Side effects joint pain 1 of 5 · other 1 of 5

Stopped 0 of 5 Used with other compounds 2 of 5

All men

7 men

small sample · n = 7

Outcome mixed 3 of 7 · positive 3 of 7 · unclear 1 of 7

Benefits fat loss 6 of 7 · less appetite 2 of 7 · gut 1 of 7 · joints / tendons 1 of 7

Side effects gi upset 1 of 7 · joint pain 1 of 7 · other 1 of 7

Stopped 0 of 7 Used with other compounds 4 of 7

Everyone

25 people

Positive: 12 of 25 (48%)
Mixed: 7 of 25 (28%)
Negative: 3 of 25 (12%)
Unclear: 3 of 25 (12%)

Benefits reported of 25

Benefits reported (n = 25)
Item	Reports
Fat loss	15 of 25 (60%)
Less appetite	6 of 25 (24%)
Joints / tendons	2 of 25 (8%)
Energy	1 of 25 (4%)
Gut	1 of 25 (4%)
Inflammation	1 of 25 (4%)
Other	1 of 25 (4%)
Strength	1 of 25 (4%)

Side effects reported of 25

Why people stopped of 25

Stopped 1 of 25 (4%) Used with other compounds 11 of 25 (44%)

User reports are anecdata, not evidence: self-selected, unverified, often combined with other compounds.

In their words

“In 10 months Ive gone from 121kg (267 lbs) to now 85.8kg (189 lbs).”

positivelate-50s M · r/Retatrutide
“Fat loss is legit”

positive48M · r/Retatrutide
“Losing noticeable strength/muscle”

side effect48M · r/Retatrutide
“I (54M) have been on Reta for 9 months and went from 235 down to 208”

positive54M · r/Retatrutide
“I HAD SO MUCH NAUSEA AND I COULD BARELY WORKOUT.”

side effectr/Retatrutide
“50M, 5'8" | 165 to145 lbs | Retatrutide progress from April to August”

positive50M · r/Retatrutide
“It completely killed the cravings... Been sober and lost 110lbs since.”

positiver/science
“I lost quite a bit of muscle mass but also didnt need all that muscle when carrying around a significantly lighter body.”

side effectr/science

Read summaries and method notes

Read 1. Four qualifying men were coded: a man approaching 60 reported substantial weight loss after ten months, a 48-year-old described rapid fat loss with muscle and strength concerns, a 54-year-old described slower weight loss and some regain, and another 54-year-old reported no noticeable heart-rate increase without giving a broader effectiveness verdict. Across all 17 selected users, reported weight and appetite changes were common, but nausea, diarrhea, elevated heart rate, and other symptoms also occurred. Some accounts described substantial effects within weeks, whereas others reported slower progress over nine months or longer. Eight reports involved other compounds or major concurrent interventions, and several users explicitly raised concerns about product authenticity or variable potency. The experiences are not a controlled sample and cannot establish the effectiveness or safety of unverified retatrutide supplies.

Read 2. One man aged 45–60: a 50M (5'8") went from 165 to 145 lb over four months with interval walking. Eight users: 5 positive, 1 mixed, 2 unclear — fast fat loss (10% of body weight in 3 months under 2 mg; 110 lb since May 2025), fewer food and alcohol cravings, less inflammation and chronic low-back pain. Side effects: raised resting heart rate (especially with MOTS-c) and lean-muscle loss. Typical 6–24 weeks at 0.5–2 mg weekly.

Note 1. The two 54M reports were from distinct accounts. The older man's Crohn's and joint improvements occurred alongside major dietary, exercise, supplement, and other treatment changes, so these are reported associations rather than retatrutide-attributable benefits. Muscle loss and skin sensitivity in the 48M report were also confounded by rapid weight reduction and other compounds. Tirzepatide-only reports were excluded. One severe adverse account described an accidentally excessive self-administered amount; this was counted as reported exposure, not a dosing recommendation. Counts are selected verifiable reports, not exhaustive tallies.

Note 2. Seed threads appearing only as sidebar links or unindexed URLs were not counted.

Each read counted people independently. Overlap between the two reads is estimated from shared threads and removed; counts are approximate. How we count.

Summary

Investigational GIP/GLP-1/glucagon receptor triple agonist peptide.

Proposed mechanism

Retatrutide is the first triple hormone receptor agonist to reach Phase 3. It activates three incretin/metabolic pathways simultaneously:

GLP-1 receptor — appetite suppression, gastric emptying, insulin secretion
GIP receptor — enhanced insulin response, adipose tissue metabolism (same target as tirzepatide's second arm)
Glucagon receptor — increased hepatic fat oxidation, resting energy expenditure, thermogenesis

The glucagon arm differentiates it from tirzepatide (Zepbound/Mounjaro). Separate-trial weight-loss percentages do not establish substantially greater fat oxidation or head-to-head superiority over dual agonists.

Safety

Dose-related gastrointestinal adverse events and treatment discontinuation
Dysesthesia varies by population and dose, up to about 21% in TRIUMPH-4
Dose-dependent heart-rate increase in phase 2
Serious adverse events more common than placebo in published knee-OA trials; causality not established by imbalance alone
No approved prescribing label or established comprehensive contraindication profile
Counterfeit product injury is distinct from authentic retatrutide trial safety

From labels, regulators and trials. No signal in small studies ≠ safe.

Legal status

US FDANot approved

Not approved; not eligible for compounding under federal law. FDA's October 2, 2026 remand letter maintains drug rather than biologic classification; sponsor disputes pathway and plans filing by Q1 2027. Approval date not found. Not on July 23-24, 2026 PCAC agenda; no applicable outcome. Source

checked 2026-11-13

WADA 2026Likely prohibited (S0)

Prohibited (S0, non-approved substances; application of class rule). Source

checked 2026-11-13

EU

EU clinical-trial registration found; EMA marketing authorisation not found. Source

checked 2026-11-13

Evidence B weight loss

B stands and is the rubric's ceiling here: A requires a regulatory approval and there is none. The evidence is far above the 'one solid RCT' bar (published phase 3 trials TRIUMPH-1, TRIUMPH-2, TRIUMPH-4 and TRANSCEND-T2D-1, all positive), so B understates the trial record but is the correct rubric grade until a regulator approves it.

Human trials · 6

PMID 373663152023RCT, double-blind, phase 2 338 people

Adults with obesity or overweight plus a weight-related condition, without diabetes

At 48 weeks, 12 mg weekly produced -24.2% weight change versus -2.1% placebo. Source
PMID 428149542026RCT, double-blind, phase 3 2,339 people

Obesity/overweight without diabetes (TRIUMPH-1)

At 80 weeks, weight change -17.6%, -23.7%, -25.0% at 4, 9, 12 mg versus -3.9% placebo; treatment-regimen estimates. Source
PMID 428103722026RCT, double-blind, phase 3 1,152 people

Obesity/overweight and T2D (TRIUMPH-2)

At 80 weeks, weight change -11.9%, -16.8%, -18.8% at 4, 9, 12 mg versus -5.1% placebo; treatment-regimen estimand. Source
PMID 422505752026RCT, double-blind, phase 3 537 people

T2D inadequately controlled by diet/exercise alone (TRANSCEND-T2D-1)

At 40 weeks, 12 mg reduced HbA1c by 1.94 percentage points versus 0.81 with placebo and weight by 15.3% versus 2.6%. Source
NCT059313672026RCT, double-blind, phase 3; topline 2025, publication November 8, 2026 445 people

Painful knee osteoarthritis and BMI at least 27, without diabetes (TRIUMPH-4)

At 68 weeks, weight change -20.0% at 9 mg and -23.7% at 12 mg versus -4.6% placebo; knee pain also improved.
NCT058820452026RCT, double-blind, phase 3; sponsor topline report 1,949 people

Severe obesity and established cardiovascular disease, with/without T2D (TRIUMPH-3); n as reported by sponsor

Sponsor reported up to 22.6% weight reduction at 80 weeks under efficacy estimand; this is not a cardiovascular event result.

Bar length = trial size on a log scale.

Dose ranges

Reported ranges from labels and studies, with context. Not a recommendation.

clinical trial
Phase 2 obesity study: target doses 1, 4, 8 or 12 mg subcutaneously once weekly for 48 weeks. Source
clinical trial
Phase 3 trials: 4, 9 or 12 mg weekly target doses (TRIUMPH-1/2/TRANSCEND-T2D-1); 9 or 12 mg in TRIUMPH-4, with protocol initiation at 2 mg and escalation. Source on a non-primary host — not linked

Editorial ratings EDITORIAL

Editors’ judgement, 0–5. Opinion, not data; separate from grade and user score.

Not rated yet.

Sources

Reddit threads read · 13

14 further sources on commercial or non-primary hosts not listed.

Research checked 2026-11-13.

Item	Reports
Other	6 of 25 (24%)
Heart rate up	3 of 25 (12%)
GI upset	2 of 25 (8%)
Nausea	2 of 25 (8%)
Joint pain	1 of 25 (4%)
Tingling / numbness	1 of 25 (4%)