Prof. PeptideProf. Peptide

Retatrutide

Metabolic & GLP-1Investigational

Last reviewed: September 20, 2026

Quick Facts

What it is
A lab-made peptide that activates three metabolic hormone receptors at once — GLP-1, GIP, and glucagon — studied for weight loss and obesity.
How it's taken
Subcutaneous injection, once weekly
Half-life
~6 days
Typical research dose
Starts at 2 mg once weekly, escalating every 4 weeks toward a 12 mg maintenance dose
Research status
Not FDA-approved — investigational (Phase 3); research use only.
On this page
  1. 1.Where to source Retatrutide
  2. 2.What is Retatrutide?
  3. 3.How does Retatrutide work?
  4. 4.What is Retatrutide used for?
  5. 5.How long does Retatrutide take to work?
  6. 6.How is Retatrutide reconstituted?
  7. 7.How is Retatrutide dosed?
  8. 8.How is Retatrutide administered?
  9. 9.What does Retatrutide stack well with?
  10. 10.What are the side effects of Retatrutide?
  11. 11.Does Retatrutide interact with other drugs?
  12. 12.How should Retatrutide be stored?
  13. 13.What are the limitations of Retatrutide research?
  14. 14.Retatrutide FAQ
  15. 15.Common questions
  16. 16.References
  17. 17.Published Studies
  18. 18.In the News

Where to source Retatrutide

Retatrutide is investigational and not available by prescription. Research-grade product is sold by specialty peptide vendors for laboratory use only. The three vendors highlighted below carry Retatrutide and have been vetted for transparent third-party testing, traceable batch documentation, and verified discount codes.

Capstone Peptides50% off
Professor's Pick

Accumark Labs · digital COAs

Shop Capstone Peptides
Peptide Partners10% off
Professor's Pick

Kovera, Chromate and BioRegen · certificates checked at each lab

Shop Peptide Partners
Glacier Aminos10% off

Batch-traceable COAs · cold-chain shipping

Shop Glacier Aminos
Ion Peptide15% off
Professor's Pick
Shop Ion Peptide
Compare prices across 48 vendors

Also stocking Retatrutide

Fusion Peptide, GenPeptide, Healius Peptides, Midwest Peptide — each carries a current price row for this compound.

Compare all 48 vendors stocking Retatrutide

See all 88 verified vendors

Latest research: TRIUMPH-1 is published (NEJM 2026): −25.0% average weight change at 12 mg over 80 weeks vs −3.9% on placebo. Lilly's May 2026 topline release also reported 30.3% at 104 weeks in an extension of participants with BMI ≥35. Read the full breakdown

What is Retatrutide?

Retatrutide (LY3437943) is a once-weekly injectable peptide developed by Eli Lilly that activates three different hormone receptors at once: GLP-1, GIP, and glucagon. The first two are the receptors targeted by existing weight-loss drugs — Semaglutide (Ozempic, Wegovy) hits GLP-1; Tirzepatide (Mounjaro, Zepbound) hits both GLP-1 and GIP — but retatrutide adds a third, glucagon, which boosts resting energy expenditure on top of the appetite-suppression effects shared across the class. That third receptor is the reason retatrutide has produced the largest weight losses ever recorded in a pharmacological trial: roughly 24% of body weight at 48 weeks in Phase 2 obesity research, with the weight-loss curve still declining at trial end. As of mid-2026, the drug is in Phase 3 trials under Eli Lilly’s TRIUMPH program, with regulatory submission targeted for late 2026 and potential approval in 2027 or 2028.

Reported benefits:

  • Significant body weight reduction in Phase 2 obesity trials (averaging ~24% at 48 weeks at the highest dose)
  • Improved glycemic control in Phase 2 type 2 diabetes trials (HbA1c reductions around 2.2%)
  • Appetite suppression and reduced food intake
  • Improvements in liver fat markers in early MASLD substudy data
  • Improvements in blood pressure and lipid profiles alongside weight loss
  • Once-weekly dosing (half-life around 6 days)

Common research dose: Published Phase 2 protocols ranged from 2 mg to 12 mg subcutaneously once weekly, with the highest weight-loss figures observed at the 12 mg dose. Protocols followed in research and user communities draw from these published dose escalations and from animal research, not from finalized human clinical guidelines.

Where to buy: PP maintains a vetted list of peptide vendors with verified discount codes. See Verified Discount Codes for current options.

What is retatrutide's half-life?

Retatrutide's reported elimination half-life is approximately 6 days, from the Phase 2 clinical pharmacokinetic data (Jastreboff et al., NEJM 2023; Coskun et al., Cell Metabolism 2022). It is an investigational compound and not FDA-approved, so this figure comes from trial data rather than from a prescribing label.

That is what places it on a once-weekly schedule: at a 6-day half-life, a weekly interval leaves roughly half of each dose still in circulation when the next one lands, so plasma levels build over the first several weeks before settling. Reaching that steady state takes about four to five half-lives, or four to five weeks.

The GLP-1 half-life calculator models that accumulation for retatrutide against semaglutide and tirzepatide; the half-life calculator plots it for any interval entered, and the peptide half-life chart lists the sourced figure alongside every other compound Prof. Peptide tracks.

How does Retatrutide work?

Retatrutide hits three metabolic receptors at once — GLP-1, GIP, and glucagon — whereas semaglutide hits just one and tirzepatide hits two. The first two receptors slow the stomach and reduce appetite (the well-known GLP-1 effects); the third receptor — glucagon — adds a separate energy-expenditure boost on top, encouraging the body to burn more fat at rest. The triple-pathway design is the reason retatrutide produces the largest weight losses ever recorded in pharmacological trials, and it’s also why it has a unique side-effect signature not seen with the dual or single agonists.

  1. GLP-1 Receptor Activation [1]. Retatrutide activates the GLP-1 receptor, which slows stomach emptying, reduces appetite, and improves insulin release in response to food. This is the same pathway used by semaglutide (Ozempic, Wegovy).
  2. GIP Receptor Activation [1]. The peptide also activates the GIP receptor, which enhances insulin signaling and supports fat metabolism. Adding GIP to GLP-1 activation is what made tirzepatide (Mounjaro, Zepbound) more effective than semaglutide.
  3. Glucagon Receptor Activation [1][2]. Retatrutide adds a third receptor — glucagon — which increases the body’s energy expenditure and encourages fat oxidation. This is the mechanism that distinguishes retatrutide from all other approved GLP-1-class drugs and explains the larger weight loss seen in trials.
  4. Combined Triple-Agonist Effect [2]. The three receptors work together to reduce appetite, slow digestion, improve insulin response, and burn more fat at rest. The dose-response curve in trials suggests retatrutide produces continued weight loss even at the 68-week mark, suggesting a plateau may not have been reached.

What is Retatrutide used for?

Retatrutide is in active Phase 3 clinical trials under Eli Lilly’s TRIUMPH program. Three Phase 3 trials are now published: TRIUMPH-1 (obesity, NEJM 2026), TRIUMPH-2 (obesity with type 2 diabetes, Lancet 2026) and TRANSCEND-T2D-1 (type 2 diabetes, Lancet 2026). TRIUMPH-4 (obesity with knee osteoarthritis) is so far a topline result in Lilly's own investor press release (Dec 2025). Additional Phase 3 readouts on cardiovascular outcomes, sleep apnea, and metabolic liver disease are expected through 2026 and into 2027 — making retatrutide a moving research target with results adding rapidly.

  1. Obesity and Weight Management [1][3][7]. TRIUMPH-1, a double-blind phase 3 trial in 2,339 adults with obesity without diabetes (NEJM 2026), reported weight changes of −17.6%, −23.7% and −25.0% at 4, 9 and 12 mg vs −3.9% on placebo over 80 weeks. TRIUMPH-4 (topline results, Eli Lilly investor press release, Dec 2025 — not yet peer-reviewed) reported 28.7% average weight loss at the 12 mg dose over 68 weeks in adults with obesity and knee osteoarthritis.
  2. Type 2 Diabetes [4][8]. TRANSCEND-T2D-1, a double-blind phase 3 trial in 537 people (Lancet 2026), reported HbA1c changes of −1.69%, −1.86% and −1.94% at 4, 9 and 12 mg vs −0.81% on placebo, and weight changes of −11.5%, −13.9% and −15.3% vs −2.6%, over 40 weeks. TRIUMPH-2 (1,152 adults with obesity and type 2 diabetes, 80 weeks) reported weight changes of −11.9%, −16.8% and −18.8% vs −5.1% on placebo.
  3. Knee Osteoarthritis [3]. TRIUMPH-4 also reported significant reductions in knee osteoarthritis pain (44-point improvement on the WOMAC pain subscale), suggesting weight loss may translate to functional improvements in joint disease.
  4. Cardiovascular Risk [5]. TRIUMPH-3 is an ongoing cardiovascular outcomes trial in patients with established cardiovascular disease. Results are expected in 2027 or later.
  5. Fatty Liver Disease (MASH) [6]. Phase 2 data showed significant reductions in liver fat and improvements in insulin sensitivity. A dedicated MASH Phase 3 trial is underway.
  6. Sleep Apnea [5]. Phase 2 data showed a 42% reduction in the apnea-hypopnea index. A dedicated obstructive sleep apnea Phase 3 trial is in the TRIUMPH program.

How long does Retatrutide take to work?

Retatrutide effects build progressively over weeks and months. Most users notice appetite reduction in the first 1–2 weeks. Meaningful weight loss accumulates over the dose-escalation phase — usually 5–7 months of steady increases. Trial data shows the weight-loss curve was still declining at the 68-week mark, suggesting plateau happens later than with semaglutide or tirzepatide.

In trials, most participants noticed reduced appetite within the first 1–2 weeks of starting. Modest weight loss (about 2–3% of body weight) typically appeared by week 4 at the 2 mg starting dose. Significant weight loss accumulated over the dose-escalation phase as the dose was increased every 4 weeks. By 24 weeks, average weight loss was around 17%; by 48 weeks, around 24%; and by 68 weeks (TRIUMPH-4), around 28.7% at the highest dose. The weight-loss curve was still declining at the end of the longest trials, suggesting full effects may take longer than 68 weeks to plateau.

How is Retatrutide reconstituted?

Retatrutide ships as a lyophilized powder that must be reconstituted before it can be measured. This is arithmetic rather than protocol: the water sets the concentration, and the concentration sets how many units on the syringe correspond to a given milligram amount. The volume chosen does not change how much peptide the vial contains.

Bacteriostatic versus sterile water. Bacteriostatic water carries 0.9% benzyl alcohol, a preservative that inhibits bacterial growth and allows a vial to be entered more than once. Sterile water has no preservative and is single-use — every entry after the first introduces organisms into a medium that will not suppress them. For a vial measured out across several occasions, that preservative is the whole distinction.

Volume, concentration, and units on a 100-unit syringe

Vial + waterConcentration2 mg4 mg6 mg9 mg12 mg
10 mg + 1 mL10 mg/mL20 units40 units60 units90 units—
10 mg + 2 mL5 mg/mL40 units80 unitsover 100over 100—
20 mg + 1 mL20 mg/mL10 units20 units30 units45 units60 units
20 mg + 2 mL10 mg/mL20 units40 units60 units90 unitsover 100

Milligram columns are the Phase 3 TRIUMPH escalation steps, listed because they are the figures the trials administered — not as a recommendation to use any of them. — marks a dose larger than the vial holds; “over 100” marks a measurement exceeding one 100-unit syringe. The arithmetic is units = (dose in mg ÷ concentration in mg/mL) × 100.

Mechanics

  1. Standard aseptic technique swabs both rubber stoppers with alcohol and lets them dry before use — wiping while still wet moves contaminants rather than killing them.
  2. Directing the water down the inside wall of the glass, rather than onto the powder directly, avoids a stream striking lyophilized peptide directly, which can denature it.
  3. Gentle swirling rather than shaking is standard, since peptides are sensitive to the shear forces agitation creates.
  4. A fully dissolved reconstitution is clear; visible particulates or cloudiness after full dissolution are the marker vendors and compounding references cite for a vial that should not be used.
  5. Refrigeration after reconstitution is standard practice: the lyophilized powder is comparatively stable, and the reconstituted solution is not.

Storage. Reconstituted peptide is held at 2–8°C and protected from light. Retatrutide has no approved product label, so there is no manufacturer-established in-use stability period to cite — this reflects general peptide handling rather than a retatrutide stability study.

Common question: How much bacteriostatic water for retatrutide?

To run these numbers for any vial size and volume, use the dosage calculator .

How is Retatrutide dosed?

Retatrutide is administered as a once-weekly subcutaneous injection. Phase 3 TRIUMPH trials use a stepwise dose-escalation protocol — starting at 2 mg and increasing every 4 weeks — to give the body time to adapt and reduce gastrointestinal side effects. The trials titrate rather than start high on the basis of Phase 2 data, which showed that beginning at 4 mg increased side-effect rates without improving outcomes.

Prof. Peptide reports what trials established and what research communities practice, labelled separately. Neither is a recommendation.

Need to calculate a dose?

Use the Prof. Peptide dosage calculator for accurate reconstitution and dosing math.

Open Calculator

Standard escalation schedule (Phase 3 TRIUMPH protocol):

  1. Weeks 1–4. 2 mg once weekly.
  2. Weeks 5–8. 4 mg once weekly.
  3. Weeks 9–12. 6 mg once weekly (TRIUMPH-3+ protocol).
  4. Weeks 13–16. 9 mg once weekly.
  5. Weeks 17+. 12 mg once weekly (maintenance, max dose tested).

Phase 2 trials tested doses from 0.5 mg to 12 mg weekly. Phase 3 (TRIUMPH-4) tested 9 mg and 12 mg as maintenance doses, with full Phase 3 results pending for the 4 mg lower-dose maintenance arm. Half-life is approximately 6 days per the Coskun et al. 2022 preclinical characterization [2], supporting once-weekly dosing with steady state reached in 4–5 weeks at each dose level.

Common question: How often is retatrutide dosed?

The TRIUMPH protocols permit an additional 4 weeks at the current step where side effects are poorly tolerated, and the published outcomes do not show that extension reducing long-term results. Splitting a weekly dose into 2–3 smaller injections is a community convention reported outside trial settings, not a protocol any trial used.

Retatrutide is not FDA-approved and is investigational. Dosing protocols outside of clinical trials are derived from trial data and user reports — there are no approved retail dosing standards.

The Prof. Peptide dosage calculator converts between milligram figures and syringe units for a given reconstitution; it performs the arithmetic and does not set a schedule.

How is Retatrutide administered?

Retatrutide is given as a subcutaneous injection — under the skin, not into muscle — once weekly, using a small insulin syringe. The injection routine, timing, and supporting habits (hydration, eating pattern, alcohol management) matter as much as the dose for tolerability. The points below cover the practical details that experienced users converge on.

  1. Route. Subcutaneous injection, once weekly. Common sites are the abdomen (avoiding a 2-inch radius around the navel), upper outer thighs, and back of the upper arms.
  2. Time of day. Any time, but consistent. Many users inject in the morning or before bed depending on side-effect timing.
  3. With or without food. Either is fine.
  4. Site rotation. Weekly site rotation, with at least an inch between consecutive sites, is the standard practice for subcutaneous GLP-1-class injections and is intended to limit localized irritation.
  5. Missed dose. Retatrutide has no approved label, so there is no missed-dose instruction for it. The convention carried over from approved once-weekly GLP-1 labels is a 5-day window — administer if fewer than 5 days have passed, otherwise skip to the next scheduled day rather than doubling.
  6. Alcohol. Alcohol compounds nausea and dehydration, and the 48 hours after injection is when levels peak. The commonly reported practice is to abstain across that window.
  7. Hydration. The compound blunts thirst signalling, so thirst becomes an unreliable cue for intake — which is why a fixed daily target rather than thirst-driven drinking is the practice users report.
  8. Eating pattern. Small meals every 3–4 hours rather than waiting for hunger, which is suppressed. Empty-stomach nausea is the most common trigger for vomiting.

Timing context. Retatrutide is administered once weekly via subcutaneous injection. Unlike short-acting GH-axis peptides, Retatrutide does not require empty-stomach administration — its long half-life produces steady-state receptor activation independent of meal timing. The two timing variables that matter most are weekly consistency (same day each week supports stable plasma levels) and time of day (many researchers inject in the evening to sleep through peak GI side effects, especially during titration).

AspectReported
FrequencyOnce weekly, same day each week
Best time of dayGI adverse reactions on GLP-1-class labels are most frequently reported during dosage escalation, per Wegovy’s own label; evening dosing to sleep through that window is a commonly reported practice, though no trial has tested timing itself.
FoodNo fasting required; inject with or without food
Injection site rotationRotating between the abdomen, thigh, and upper arm without reusing the same site for the next injection is standard subcutaneous-injection practice — documented in FDA-approved injectable labels generally (e.g., Wegovy's and Mounjaro's own instructions to rotate with each dose), not specific to Retatrutide.
WeekTypical doseNotes
1–40.5–1 mg weeklyInitial titration; assess GI tolerance
5–82 mg weeklyFirst dose increase if titration is tolerated
9–124 mg weeklySecond escalation
13+6–12 mg weeklyMaintenance, dose-dependent on protocol goal

*Phase 3 trial doses ranged 1–12 mg weekly. Lower doses (1–4 mg) targeted weight reduction in obesity studies; higher doses (8–12 mg) were used in maximum-effect arms. Those trials titrated the dose upward slowly, citing gastrointestinal side effects as the reason.

Reconstitution math. Water volume sets concentration, and concentration sets the syringe-unit conversion — see how Retatrutide is reconstituted above for the mechanics, and retatrutide reconstitution calculator for the arithmetic worked across every vial size Prof. Peptide tracks across vendors, not a single assumed size.

Trial doses, read directly. Retatrutide has no approved product and no label, so the doses above are trial doses, not a schedule — see how is retatrutide dosed for each Phase 2 and Phase 3 TRIUMPH trial by NCT number, arm, and the adverse events reported at each dose.

What does Retatrutide stack well with?

Retatrutide’s triple-agonist mechanism is strong enough that standalone use is the most common research protocol — additional incretin-class peptides usually amplify side effects without proportional benefit. The cleanest additions are non-peptide: resistance training, adequate protein, and metformin in diabetes contexts. The things to avoid are other GLP-1-class compounds and stacks that would compound the same receptor pathways.

  1. Standalone use. The most common research protocol. Retatrutide's triple-agonist effect is strong enough that stacking with other GLP-1-class peptides is unnecessary and can compound side effects.
  2. Metformin. Commonly used together in type 2 diabetes for additive blood-sugar control. Standard practice in clinical settings.
  3. Resistance training + 1.2–1.6 g/kg protein. This is the countermeasure cited in the GLP-1 clinical literature for preserving lean muscle mass during rapid weight loss. Without this, GLP-1-class drugs can cause significant muscle loss alongside fat loss.
  4. GH-axis peptides for lean-mass preservation. GH Stack (CJC-1295 + Ipamorelin) or MK-677 are sometimes added during caloric restriction to support lean-mass retention via elevated IGF-1. Side-effect profiles do not overlap meaningfully with retatrutide.
  5. Tissue-repair peptides during rapid weight loss. Wolverine Stack (BPC-157 + TB-500) or the broader GLOW / KLOW blends are sometimes used for joint and connective-tissue support during the higher-strain phase of significant weight loss.
  6. Conflicts: other GLP-1 agonists. Semaglutide, tirzepatide, or liraglutide should not be combined with retatrutide. Combining incretin-based drugs significantly increases GI side effects without proportional benefit.
  7. Conflicts: CagriSema or standalone cagrilintide on top. CagriSema (semaglutide + cagrilintide) overlaps with retatrutide's GLP-1 arm. Cagrilintide alone is amylin-based and is less directly overlapping but has limited combination data with retatrutide.

What are the side effects of Retatrutide?

Retatrutide’s side-effect profile resembles other GLP-1-class drugs — gastrointestinal effects dominate, especially during dose escalation — with one important difference: dysesthesia (abnormal skin sensations) was reported in about 21% of participants at the 12 mg dose in TRIUMPH-4. This is unique to retatrutide and not seen with semaglutide or tirzepatide. The mechanism is thought to relate to glucagon-receptor activity.

Common (most users)

  1. Nausea. Most common, especially during dose escalation; affected up to 60% at 12 mg in Phase 2.
  2. Diarrhea. Affected 15–33% of users at higher doses.
  3. Constipation. Affected 11–25% of users.
  4. Vomiting. Affected 21–26% of users at higher doses.
  5. Decreased appetite. Expected effect, but can be excessive in some users.
  6. Injection site reactions. Mild redness or irritation in up to 8% of users.

Less common (moderate)

  1. Dysesthesia. Abnormal skin sensations including tingling, burning, or prickling. Reported in about 21% of participants at 12 mg in TRIUMPH-4. Specific to retatrutide and not seen with semaglutide or tirzepatide.
  2. Increased heart rate. Average increase of 5–10 beats per minute, peaking around week 24 and then declining.
  3. Headache and fatigue. Typically mild, common in the 48–72 hours after injection.
  4. Mild liver enzyme elevations. Transient ALT increases in about 1% of users.

Serious (rare — call a doctor)

  1. Pancreatitis. About 0.4% in Phase 2 trials. Symptoms: severe abdominal pain radiating to the back, persistent vomiting, fever.
  2. Gallbladder problems. About 1.1% in trials. Symptoms: severe pain in upper right abdomen, jaundice, fever.
  3. Severe allergic reactions. Rare. Symptoms: difficulty breathing, swelling of face/throat, hives. Seek emergency care.
  4. Heart rhythm changes. Slightly more common with retatrutide (about 6% vs 3% placebo).

Most side effects are mild to moderate and improve as the body adapts. Discontinuation due to side effects ranged from 6% to 16% in Phase 2 trials, with most discontinuations during the escalation phase. The serious adverse event rate was 4% — the same as placebo.

Does Retatrutide interact with other drugs?

Retatrutide has several important drug interactions, most notably with other blood-sugar-lowering medications (insulin, sulfonylureas), oral medications that depend on stomach emptying for absorption, and other GLP-1-class drugs. Alcohol compounds nausea and dehydration. The interactions below are the ones most relevant in research and clinical contexts.

  1. Insulin and sulfonylureas. Risk of hypoglycemia (low blood sugar) increases when retatrutide is combined with insulin, glipizide, glyburide, or other blood-sugar-lowering drugs. Dose adjustment is typically needed.
  2. Oral medications. Retatrutide slows stomach emptying, which can affect the absorption of oral medications. Particularly relevant for medications with a narrow therapeutic window (warfarin, levothyroxine, certain antibiotics).
  3. Birth control pills. Slowed gastric emptying may reduce absorption. Some manufacturers recommend backup contraception during the first 4 weeks of treatment and 4 weeks after each dose increase.
  4. GLP-1 agonists (semaglutide, tirzepatide, liraglutide). Should not be combined.
  5. Alcohol. Compounds nausea, dehydration, and hypoglycemia risk.

How should Retatrutide be stored?

  1. Lyophilized (powder) form: sealed and refrigerated at 2–8°C is the standard storage condition reported for peptide powders generally. Retatrutide has no approved product and therefore no manufacturer-stated shelf life to cite.
  2. Reconstituted solution: 2–8°C, refrigerated, is standard practice once dissolved. Prof. Peptide has not identified a manufacturer label, published study, or lab document establishing how long reconstituted research-grade retatrutide remains stable — a figure once stated here ("stable for 28–30 days") had no cited source and has been removed. A vendor's own product page may state a shelf-life figure; that is the vendor's claim, not an independently verified one.
  3. Reconstitution: dissolving in bacteriostatic water for injection (BAC water) at the volume the dosage calculator is given is standard practice. Gentle swirling rather than shaking is standard.
  4. Freezing is avoided in standard peptide handling, since it is reported to damage the peptide and render it inactive.
  5. Protection from light — storage in the original container or a light-protective container — is standard practice.
  6. A solution that is cloudy, discolored, or contains particles is the marker vendors and compounding references cite for one that should not be used.

What are the limitations of Retatrutide research?

Retatrutide is an investigational drug, not approved by the FDA, EMA, or any major regulatory body. As of May 2026, it is in Phase 3 trials with potential approval in 2027 or 2028. Long-term safety data beyond 72 weeks does not yet exist. The dysesthesia signal at higher doses is unique to retatrutide and the safety concern being monitored most closely.

Retatrutide is an investigational drug and is NOT approved by the FDA, EMA, or any major regulatory body. As of May 2026, it is in Phase 3 clinical trials. Eli Lilly’s Phase 3 TRIUMPH program is expected to complete additional readouts throughout 2026, with regulatory submission to the FDA targeted for late 2026 and potential approval in 2027 or 2028.

Long-term safety data beyond 72 weeks does not yet exist — all current trials are 48 to 68 weeks. Cardiovascular outcomes trial (TRIUMPH-3) results are not expected until 2027 or later. The dysesthesia signal observed in Phase 3 (about 21% at 12 mg) is unique to retatrutide and is being monitored closely.

Retatrutide is not currently a scheduled controlled substance in the US, but it is also not approved for human use. Research-grade product is sold in a regulatory gray area, typically labeled “for research use only, not for human consumption.” The World Anti-Doping Agency prohibits all GLP-1-class drugs in sport. Legal status varies by country.

Retatrutide FAQ

Is retatrutide FDA-approved?

No. Retatrutide is investigational and not approved by the FDA, EMA, or any major regulatory body. It is in Phase 3 clinical trials as of May 2026, with potential approval in 2027 or 2028.

How does retatrutide compare to semaglutide and tirzepatide?

Semaglutide activates one receptor (GLP-1). Tirzepatide activates two (GLP-1 + GIP). Retatrutide activates three (GLP-1 + GIP + glucagon). Trial weight loss has been progressively higher with each: semaglutide around 15%, tirzepatide around 22%, retatrutide around 28.7% at the highest doses. Retatrutide also has a unique side effect — dysesthesia (skin sensation changes) — that doesn't appear with the other two.

How long does retatrutide take to work?

Most users notice reduced appetite within 1–2 weeks. Modest weight loss appears by week 4. Significant weight loss accumulates over the dose-escalation phase. Average weight loss was about 17% by week 24, 24% by week 48, and 28.7% by week 68 in trials.

Does retatrutide cause muscle loss?

Like all GLP-1-class drugs, retatrutide can cause loss of lean muscle alongside fat loss, especially during rapid weight reduction. In the GLP-1 literature, resistance training and higher protein intake (studies typically use 1.2–1.6 g/kg body weight per day) are associated with reduced lean-mass loss; no retatrutide-specific trial has tested either.

What is dysesthesia and should I be concerned?

Dysesthesia means abnormal skin sensations — tingling, burning, or pins-and-needles feeling. It was reported in about 21% of participants at the 12 mg dose in TRIUMPH-4. The effects were generally mild and rarely led to discontinuation. It's specific to retatrutide and not seen with semaglutide or tirzepatide. The mechanism is not fully understood but is thought to relate to glucagon-receptor activity.

What happens if I stop retatrutide?

Long-term data on what happens after stopping is still limited. Based on data from semaglutide and tirzepatide, partial weight regain is expected after discontinuation. The TRIUMPH-6 trial is studying maintenance strategies including dose reduction; results are expected in 2026.

Can I drink alcohol on retatrutide?

Alcohol compounds nausea and dehydration. The commonly reported practice is to abstain for the 48 hours after each weekly injection, when levels peak. Alcohol also increases hypoglycemia risk in users with type 2 diabetes.

Where can I get retatrutide?

Retatrutide is investigational and not available by prescription. Research-grade product is sold by peptide vendors for laboratory use only. PP maintains a list of vetted vendors with verified discount codes — see Verified Discount Codes .

Common questions

Each of these answers one question on its own page. The profile is the place for mechanism, evidence, and safety in context; these are for the specific thing someone typed into a search box.

References

  1. Jastreboff AM, Kaplan LM, Frías JP, et al. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. N Engl J Med. 2023;389:514-526. https://www.nejm.org/doi/full/10.1056/NEJMoa2301972
  2. Coskun T, Urva S, Roell WC, et al. LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss. Cell Metab. 2022;34(9):1234-1247. https://pubmed.ncbi.nlm.nih.gov/35985340/
  3. Eli Lilly. Lilly's triple agonist, retatrutide, delivered weight loss of up to an average of 71.2 lbs along with substantial relief from osteoarthritis pain in first successful Phase 3 trial (TRIUMPH-4). December 11, 2025. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-weight-loss-average
  4. Bajaj HS, Welch M, Shah P, et al. Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial. Lancet. 2026;407:2402-2413. PMID 42250575. https://pubmed.ncbi.nlm.nih.gov/42250575/
  5. Eli Lilly. TRIUMPH Phase 3 Clinical Trial Program. https://www.lilly.com/discovery/clinical-development
  6. Sanyal AJ, Kaplan LM, Frías JP, et al. Retatrutide for adults with metabolic dysfunction-associated steatotic liver disease: a Phase 2 trial. Nat Med. 2024;30:1235-1244. https://pubmed.ncbi.nlm.nih.gov/38858523/
  7. Jastreboff AM, Kaplan LM, Davies MJ, et al. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1). N Engl J Med. 2026. PMID 42814954. https://pubmed.ncbi.nlm.nih.gov/42814954/
  8. Bellido V, le Roux CW, Ekinci EI, et al. Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial. Lancet. 2026;408:1455-1472. PMID 42810372. https://pubmed.ncbi.nlm.nih.gov/42810372/

Published Studies

Plain-English summaries of the peer-reviewed studies behind the claims above. Click any title to read the source paper.

New England Journal of Medicine · 2023Open Access
Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial →

Jastreboff AM, Kaplan LM, Frías JP, et al. — Retatrutide Phase 2 Obesity Trial Investigators

The landmark Phase 2 trial of retatrutide in 338 adults with obesity. At the highest dose (12mg), participants lost an average of 24.2% of their body weight over 48 weeks — with weight loss curves that had not yet plateaued at trial end, suggesting even greater losses with longer treatment. Every single participant in the 12mg group achieved at least 5% weight loss, and 62% achieved 20% or more. These are the highest weight loss numbers ever recorded in a pharmacological trial and exceed those of bariatric surgery in some comparisons.

The Lancet · 2023Open Access
Retatrutide for People with Type 2 Diabetes — A Phase 2 Trial →

Rosenstock J, Frias JP, Jastreboff AM, et al.

Companion Phase 2 trial of retatrutide in 281 adults with type 2 diabetes. Retatrutide produced significant reductions in HbA1c (up to 2.02 percentage points) and body weight (up to 16.94%) compared to placebo over 36 weeks. The triple agonist mechanism improved glycemic control more than existing single and dual agonists, while also producing substantial weight loss — establishing the metabolic breadth of the compound beyond obesity alone.

ClinicalTrials.gov · 2024–2026 (ongoing)Open Access
TRIUMPH Phase 3 Program — Trial Status and Design →

ClinicalTrials.gov

Retatrutide entered Phase 3 clinical trials under the TRIUMPH program in 2024, with seven trials evaluating it across obesity, type 2 diabetes, cardiovascular outcomes, and related metabolic conditions. As of early 2026 Phase 3 results are beginning to emerge. If the Phase 3 data replicates the Phase 2 findings, retatrutide would represent the most effective pharmacological weight loss treatment ever approved. This page will be updated as Phase 3 results are published.

Weight LossMetabolic HealthTriple AgonistInvestigational

Related Peptides

TirzepatideSemaglutideCagrilintideCagriSemaMK-677

Related Blends

Wolverine StackGH StackGLOWKLOW

Comparisons

Retatrutide vs Tirzepatide Retatrutide vs Semaglutide Semaglutide vs Tirzepatide vs Retatrutide

We may earn commissions from peptide vendor affiliate links.

Have a question about Retatrutide? Send us an email