Not medical advice. Talk to your provider before using any peptide.
Full disclaimer
Retatrutide35 residues (approx.)YQGTFTSDYSILDKKAQAFIEYLLEGGPSSGAPPPSEach bubble = one amino acid. Size = residue mass. Color = chemical class.Uses closest standard amino acids for non-standard residues.Also known as: LY3437943, LY-3437943, Triple G
28.7% mean body weight reduction at 68 weeks. That number, from the Phase 3 TRIUMPH-4 trial in 445 adults, makes the retatrutide peptide (LY3437943) the most effective weight-loss compound ever tested in a clinical trial. It works by activating three receptors at once: GLP-1, GIP, and glucagon. The glucagon piece is what separates it from tirzepatide and semaglutide, driving direct hepatic fat oxidation and higher resting energy expenditure. Still in Phase 3 trials with no FDA approval yet, so access today means compounding pharmacies or clinical trial enrollment. GI side effects during titration are real and often intense.
28.7% mean body weight gone in 68 weeks. That Phase 3 number from TRIUMPH-4 (n=445, December 2025) set a new ceiling for obesity pharmacotherapy. No other drug, approved or investigational, has matched it. The retatrutide peptide (LY3437943, CAS 2381089-83-2) is a 44-amino-acid synthetic lipopeptide developed by Eli Lilly. Known in community forums as reta peptide or Triple G, it activates GLP-1, GIP, and glucagon receptors simultaneously in a single molecule. The GLP-1 component suppresses appetite and slows gastric emptying. GIP improves insulin response and buffers GLP-1 tolerability. Glucagon raises resting energy expenditure and burns liver fat directly. That third receptor is the differentiator; dual agonists like tirzepatide lack it entirely. Clinicians and researchers tracking the obesity pharmacotherapy space have been watching retatrutide since the Phase 2 readout (Jastreboff et al., NEJM 2023)[1], where 338 adults lost up to 24.2% body weight at 48 weeks on the 12 mg dose. A separate Phase 2a MASLD trial (Nature Medicine 2024)[2] showed 82.4% relative liver fat reduction in 98 participants at 24 weeks. Seven more Phase 3 TRIUMPH trials are still reading out. Community users who plateaued on semaglutide or tirzepatide have driven early adoption through compounding pharmacies. The enthusiasm is high; so are the GI side effects during dose escalation. NDA submission is expected in late 2026 or early 2027. Until then, retatrutide carries no FDA approval and no insurance coverage.
Three receptors. One molecule. Retatrutide binds GLP-1, GIP, and glucagon receptors simultaneously, making it the only triagonist in late-stage clinical development. GLP-1 receptor activation suppresses appetite centrally through hypothalamic satiety pathways and slows gastric emptying peripherally. This is the same mechanism behind semaglutide and liraglutide. GIP receptor agonism potentiates glucose-dependent insulin secretion from pancreatic beta cells while improving tolerability of GLP-1 effects on the gut. Tirzepatide uses GLP-1 plus GIP; retatrutide adds a third target. The glucagon receptor component is what makes this molecule different. Glucagon activation increases resting energy expenditure and promotes hepatic fat oxidation, converting liver triglycerides to ketone bodies. Phase 2a MASLD data [2] confirmed this clinically: 82.4% relative liver fat reduction at 12 mg in 24 weeks. That degree of liver fat clearance exceeds anything reported with GLP-1 or dual-agonist therapy. The triple mechanism produces additive weight loss because each receptor targets a distinct metabolic pathway. Appetite drops. Energy expenditure rises. Liver fat burns off. The result, based on Jastreboff's Phase 2 [1] and TRIUMPH-4 Phase 3 data, is weight loss that exceeds all prior single or dual-agonist results.
Phase 3 TRIUMPH-4 (Dec 2025) confirmed 28.7% mean body weight reduction at 68 weeks with 12 mg: the highest efficacy ever recorded in an obesity pharmacotherapy trial. Phase 2 demonstrated 24.2% at 48 weeks [1]. MASLD Phase 2a showed up to 82.4% liver fat reduction at 24 weeks [2]. Evidence base is strong across three completed trials; 7 additional Phase 3 readouts pending in 2026.
TRIUMPH-4 Phase 3 (Lilly press release, Dec 11 2025): n=445 adults with obesity + knee OA; 12 mg = −28.7% body weight, 9 mg = −26.4% at 68 weeks. Phase 2 obesity (Jastreboff et al., NEJM 2023, PMID 37366315): n=338, −24.2% at 48 wk (12 mg). MASLD Phase 2a (Nature Medicine 2024, PMID 38858523): n=98, −82.4% relative liver fat at 24 wk (12 mg).
Not yet FDA approved; NDA submission expected late 2026 / early 2027. Only one Phase 3 readout (TRIUMPH-4) published to date; remaining TRIUMPH trials pending. No cardiovascular outcomes trial data yet. Dose-dependent resting heart rate increase observed in Phase 2: appears manageable in Phase 3 but requires monitoring. Long-term data beyond 68 weeks absent. Weight regain on discontinuation expected (GLP-1 class effect).
Referred to as "Godzilla" and "Triple G" in weight-loss communities. High enthusiasm from users who plateaued on semaglutide or tirzepatide. Compounded versions widely used despite investigational status. Stronger and faster appetite suppression than class peers reported, but GI side effects and heart rate elevations are the primary complaints.
Community titration closely mirrors Phase 2 trial design. Efficacy expectations align with clinical data. Community awareness of heart rate and GI side effects matches Phase 2 safety signals. Community caution about product quality is appropriate given non-approved status.
| Level | Dose / Injection | Frequency |
|---|---|---|
| Beginner | 1mg | Weekly |
| Moderate | 4mg | Weekly |
| Aggressive | 8mg | Weekly |
Retatrutide dosing starts at 1 mg weekly regardless of prior GLP-1 experience. The triple-receptor mechanism means your gut is adapting to three agonists at once, not just one. Even users who tolerated tirzepatide at high doses report rougher GI onboarding with retatrutide. Reconstitution math for common vial sizes: a 10 mg vial with 2 mL bacteriostatic water gives you 5 mg/mL. At that concentration, 1 mg equals 0.2 mL, which is 20 units on a standard 100-unit insulin syringe. A 4 mg dose would be 80 units. For the 12 mg maintenance dose, you'll want a 15 mg vial with 2 mL BAC water (7.5 mg/mL); 12 mg then equals 1.6 mL or 160 units. At 160 units, consider splitting across two injection sites to reduce volume discomfort. Track your resting heart rate from day one. The glucagon component raises energy expenditure, and HR is the clearest early signal of dose-dependent cardiovascular stress. If your resting pulse sits above 90 bpm for more than a week, hold the current dose before escalating. Evening injections let you sleep through peak nausea, which typically hits 4 to 8 hours post-injection.
Retatrutide is not FDA approved and lacks long-term safety data beyond 68 weeks. Cycling decisions are primarily driven by the need for periodic safety evaluation (heart rate, metabolic markers, liver function) rather than established receptor desensitization. Weight regain on discontinuation is a consistent GLP-1 class effect: continuous use appears necessary for sustained weight maintenance, consistent with its positioning as a chronic disease therapy.
Or use the universal Peptide Calculator for any peptide.
Expected: 24.2% mean body weight loss at 48 weeks (Phase 2, 12 mg); 28.7% at 68 weeks (Phase 3 TRIUMPH-4, 12 mg). Up to 82.4% liver fat reduction in MASLD subgroup (Phase 2a, 12 mg).
Monitor: Check resting heart rate weekly during titration. Lipid panel and liver enzymes at baseline and 12 weeks. Blood glucose monitoring if diabetic or pre-diabetic.
Clean the top of your lyophilized retatrutide vial with an alcohol swab. Draw 2 mL of bacteriostatic water into a syringe and inject it slowly down the inner wall of the vial. Do not shake. Swirl gently until the powder dissolves completely.
With a 10 mg vial and 2 mL BAC water, your concentration is 5 mg/mL. For a 1 mg dose, draw 20 units on a 100-unit insulin syringe. For 2 mg, draw 40 units. For 4 mg, draw 80 units. For 8 mg, draw 160 units (or use a 15 mg vial at 7.5 mg/mL for higher doses; 8 mg then equals approximately 107 units).
Pinch a fold of skin at your injection site (abdomen, outer thigh, or upper arm). Insert a 29 to 31 gauge needle at a 45 to 90 degree angle. Inject slowly. Hold for 5 seconds before withdrawing.
Never inject the same quadrant within two weeks. Abdomen is preferred for absorption consistency.
Evening dosing is preferred so peak nausea (4 to 8 hours post-injection) occurs during sleep.
Store the reconstituted vial refrigerated at 2 to 8 degrees Celsius. Use within 4 weeks.
Both agents activate GLP-1 receptors. Combining GLP-1 agonists stacks GI side effects (nausea, vomiting, gastroparesis) with no incremental efficacy benefit: retatrutide's GLP-1 component already provides full GLP-1 agonism.
Do not combineTirzepatide is a GLP-1/GIP dual agonist. Combining with retatrutide creates redundant GLP-1 and GIP receptor activation with compounding GI risk and no clinical rationale.
Do not combineAdding a fixed-dose GLP-1 combination on top of a triple GLP-1/GIP/glucagon agonist introduces overlapping GLP-1 activity and entirely unstudied additive risk.
Do not combineRetatrutide's GLP-1 and GIP components both lower blood glucose; combining with insulin or sulfonylureas increases hypoglycemia risk, especially in type 2 diabetes. Medical supervision required.
Pricing updated 2026-04-09
Gastrointestinal events during dose escalation are the defining tolerability challenge with retatrutide, and they hit harder than comparable GLP-1 agents at equivalent titration speeds. In TRIUMPH-4 Phase 3 data [5], nausea occurred in 38 to 43% of participants. Diarrhea affected 33 to 35%. Constipation hit 22 to 25%. Vomiting was reported in 21%. These rates are dose-dependent and front-loaded, meaning they peak during the weeks immediately after each dose increase. Most GI events resolve within 1 to 2 weeks at a stable dose. Slow titration from 1 mg with 4-week steps between escalations reduces severity substantially. Raised resting heart rate is the second signal that deserves attention. Phase 2 trials [1] documented a dose-dependent increase in resting HR tied to glucagon receptor activation. Community users at 8 mg and above have reported palpitations and sustained HR above 90 bpm. Phase 3 data suggests this effect is manageable with proper monitoring, but anyone with a cardiac history should track heart rate weekly during titration. Do not escalate if resting HR stays above 100 bpm. Post-injection fatigue, sometimes called "wipeout day," shows up consistently in community reports at doses of 8 mg or higher. Users describe pronounced fatigue lasting 12 to 24 hours after injection, particularly during the first 2 to 4 weeks at a new dose level. Scheduling the injection on a low-demand day helps. The GLP-1 class carries an unresolved rodent thyroid C-cell tumor signal. No confirmed human thyroid cancer risk has been established for any GLP-1 agonist, but retatrutide is contraindicated in anyone with a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN2). Pancreatitis is a known class risk. Severe persistent abdominal pain radiating to the back warrants immediate medical attention and discontinuation. Pregnancy is an absolute contraindication. No reproductive toxicity data exist for retatrutide. Discontinue well before any planned pregnancy. Product quality adds a layer of risk specific to investigational peptides. Retatrutide is not FDA approved; compounded versions lack standardized formulation. Request a Certificate of Analysis with HPLC purity data for every batch. Grey-market research chemicals carry contamination and identity risks that cannot be verified.
Verify Retatrutide dosing and safety with a second opinion
Retatrutide is not FDA approved. Available only through clinical trial participation or compounding pharmacies. No standardized formulation exists. Compounded versions lack regulatory verification of peptide purity and dosing accuracy. Grey-market research chemical sources carry additional contamination and peptide identity risks.
| Test | When | Target |
|---|---|---|
| Resting heart rate | Weekly during titration; monthly at stable dose | <90 bpm at rest; pause dose escalation if sustained >100 bpm; consult prescriber |
| Fasting glucose / HbA1c | Baseline, then every 3 months | Fasting glucose 70–100 mg/dL; HbA1c <5.7% (non-diabetic range) |
| Lipid panel (LDL, non-HDL, triglycerides, hsCRP) | Baseline, 12 weeks, then every 6 months | — |
| Liver enzymes (ALT, AST) | Baseline, then every 3 months in first year | — |
| Body weight + waist circumference | Weekly during active titration; biweekly at maintenance | — |
| Blood pressure (systolic/diastolic) | Monthly | — |
| Thyroid function (TSH) | Baseline; annually or if symptomatic | — |
Dose-dependent resting HR increase observed in Phase 2 trials. Glucagon receptor activation raises energy expenditure and may elevate HR. Confirmed manageable in Phase 3 but requires monitoring at each dose escalation step.
Net effect is glucose-lowering (GLP-1/GIP dominant over glucagon at therapeutic doses), but monitoring is essential in diabetic patients and those on insulin or sulfonylureas where hypoglycemia risk is elevated.
Phase 3 TRIUMPH-4 showed significant reductions in non-HDL cholesterol, triglycerides, and hsCRP at 12 mg. Baseline values are needed to quantify benefit and catch any anomalous changes.
Retatrutide is under Phase 3 investigation for MASLD. Monitoring confirms therapeutic liver enzyme normalization and detects any drug-related hepatic stress.
Primary efficacy endpoint. Weekly tracking guides titration decisions and identifies early non-response.
Phase 3 showed reduction in systolic BP at 12 mg. Patients on antihypertensives may need dose adjustment as BP falls alongside weight loss.
GLP-1 class carries an unresolved rodent thyroid C-cell tumor signal. No confirmed human risk, but TSH monitoring is standard precaution for GLP-1 receptor agonists.
Titration initiation. Mild appetite reduction begins. GI side effects (nausea, decreased appetite) are most common early. Body adjusts to triple-receptor activation.
Appetite suppression becomes more pronounced. Early weight loss of 3-5%. GI side effects typically begin to ease as the body adapts to escalating doses.
Steady weight loss accelerates. Liver fat reduction becomes measurable. Blood sugar and lipid markers improve. Most users experience 8-12% body weight reduction.
Approaching full therapeutic dose. Clinical trials showed ~17.5% mean weight loss at 24 weeks. Significant metabolic improvements across multiple markers.
Full dose maintenance. Phase 2 trials showed up to 24.2% body weight loss at 48 weeks. Liver fat reduced by over 80% at higher doses. Weight loss rate slows as a new equilibrium is reached.
Weeks 1 to 4 (1 mg): This is a GI adaptation step, not a therapeutic dose. Science expects minimal weight change. Community users report appetite suppression beginning within 3 to 5 days, though the intensity varies widely. Nausea, decreased appetite, and fatigue are most common here. Injection site redness happens. The body is adjusting to triple-receptor activation for the first time. Weeks 5 to 12 (2 to 4 mg): Weight loss becomes measurable. Phase 2 data shows 5 to 8% body weight reduction beginning in this dose range. Community users report 1 to 1.5 lbs per week and describe food noise as significantly reduced. GI events generally ease as the body adapts to a stable dose. Resting heart rate may start climbing; track it weekly from this step forward. Liver fat reduction becomes detectable at 4 mg in the MASLD subgroup. Weeks 13 to 24 (4 to 8 mg): The therapeutic range. Phase 2 showed approximately 17.5% mean weight loss at 24 weeks across the highest-dose groups. Community users call this the "sweet spot," reporting 1.5 to 2.5 lbs per week with manageable side effects. Liver fat drops sharply: 57% reduction at 4 mg and 81.4% at 8 mg in the Phase 2a MASLD trial [2]. Heart rate elevation is most prominent entering 8 mg. Post-injection fatigue may appear. Weeks 25 to 68+ (8 to 12 mg): High-dose maintenance. Phase 2 data showed 24.2% body weight reduction at 48 weeks on 12 mg [1]. TRIUMPH-4 Phase 3 pushed that to 28.7% at 68 weeks. Liver fat reaches its lowest point by week 24. Blood pressure, non-HDL cholesterol, triglycerides, and hsCRP all improved in TRIUMPH-4. Weight loss rate slows as the body approaches a new equilibrium. Some users step down from 12 mg to 8 mg, trading modest efficacy for better tolerability. Heart rate elevations are most prominent at 12 mg but generally stabilize with sustained time at dose.
Tolerability establishment. Minimal weight change expected at 1 mg: this dose is a GI adaptation step, not a therapeutic target.
Appetite suppression begins within 3–5 days in most users. Hunger reduction noticeable even at 1 mg for many, though highly variable between individuals.
Phase 2 data shows 5–8% body weight reduction beginning in this dose range. Liver fat reduction detectable at 4 mg in MASLD subgroup.
Measurable weight loss. Most users report 1–1.5 lbs/week. Cravings and food noise significantly reduced. Energy improving alongside early weight loss.
Phase 2 showed ~17.5% mean weight loss across highest-dose groups at week 24. Liver fat measurably reduced (−57% at 4 mg, −81.4% at 8 mg in MASLD Phase 2a).
Strong weight loss continues. Many users report 1.5–2.5 lbs/week. This range is commonly described as the "sweet spot": high efficacy with manageable tolerability.
Phase 2: −24.2% body weight at 48 weeks (12 mg). Phase 3 TRIUMPH-4: −28.7% at 68 weeks (12 mg). Liver fat reaches nadir by week 24. BP, non-HDL cholesterol, triglycerides, and hsCRP all improved in TRIUMPH-4.
Weight loss rate slows as a new equilibrium is approached. Metabolic labs often visibly improved. Some users reduce from 12 mg to 8 mg for better tolerability with modest efficacy trade-off.
Source: NEJM Phase 2 Trial (NCT04881706), ~6 days
Loading the interactive decay curve.
Retatrutide (LY3437943) is an investigational drug. It has not received FDA approval for any indication. Eli Lilly has multiple Phase 3 TRIUMPH trials underway; NDA submission is projected for late 2026 or early 2027. Access outside clinical trials is limited to compounding pharmacies. 503B outsourcing facilities provide more regulatory oversight than 503A pharmacies and are the preferred source. Compounded retatrutide is not equivalent to the investigational product used in Lilly's trials, and no regulatory body has verified its purity or dosing accuracy. For athletes subject to anti-doping testing, GLP-1 receptor agonists are not currently prohibited by WADA. However, retatrutide's investigational status could raise complications depending on sport-specific rules. Check with your sport's governing body before use. All content on this page is for educational and informational purposes only. It does not constitute medical advice. Consult a licensed healthcare provider before using any investigational compound.
Peptide Schedule Research TeamReviewed Apr 202615 Citations
