Retatrutide vs tirzepatide: trial results and status

Which is better, tirzepatide or retatrutide?

Tirzepatide wins on regulatory status and evidence maturity: it has approved labels, trials in thousands of participants, and a completed cardiovascular outcomes program, while retatrutide has phase 2 obesity data in a few hundred people, no approval anywhere, and no lawful access outside a clinical trial. Retatrutide's larger weight loss is real but comes from a smaller, shorter trial that is not directly comparable, and its glucagon activity raises heart rate more. If retatrutide is approved after the TRIUMPH phase 3 program, this verdict should be revisited. [1] [3] [6] [7] [8] [10]

How do tirzepatide and retatrutide compare?

Tirzepatide and Retatrutide compared by dimension
Dimension	TirzepatideFavored	Retatrutide
Mechanism [3] [7]	Dual GIP and GLP-1 receptor agonist.	Triple GIP, GLP-1, and glucagon receptor agonist; the glucagon component raises energy expenditure and liver fat oxidation.
Weight loss in the pivotal trial [1] [3] [11]	15.0%, 19.5%, and 20.9% at 5, 10, and 15 mg vs 3.1% placebo at 72 weeks in SURMOUNT-1 (2,539 adults).	8.7%, 17.1%, 22.8%, and 24.2% at 1, 4, 8, and 12 mg vs 2.1% placebo at 48 weeks in the phase 2 trial (338 adults). TRIUMPH-1 phase 3 topline: 19.0%, 25.9%, and 28.3% at 4, 9, and 12 mg vs 2.2% placebo at 80 weeks (company release, not peer reviewed).
Note: Different trials, populations, and durations; no head-to-head trial exists, so the numbers cannot be compared directly.
Evidence maturity [1] [2] [4] [5] [6] [11]	Multiple phase 3 trials in obesity (SURMOUNT) and type 2 diabetes (SURPASS), including a head-to-head win over semaglutide 1 mg in SURPASS-2 and FDA review of the full data package.	Phase 2 in obesity and type 2 diabetes plus one published phase 3 type 2 diabetes trial (TRANSCEND-T2D-1, 537 adults, 40 weeks). Phase 3 obesity trials (TRIUMPH) have reported topline results by press release; full papers, FDA review, and a cardiovascular outcomes trial are still pending.
Regulatory status [7] [8] [9]	FDA approved: Mounjaro (May 2022) and Zepbound (November 2023, sleep apnea indication added December 2024). Shortage-based compounding ended in early 2025.	Not approved by FDA or any other regulator. Not a component of an approved drug and not on the 503A bulks list, so it cannot lawfully be compounded. Only lawful access is a registered clinical trial.
WADA status [10]	Not on the WADA Prohibited List.	Prohibited at all times under section S0 (non-approved substances).
Side effects [1] [3] [7]	Nausea up to 31%, diarrhea up to 23%, vomiting up to 12%, constipation up to 12% at 15 mg in SURMOUNT-1; boxed warning for thyroid C-cell tumors; pancreatitis and gallbladder disease warnings.	Dose-related nausea, diarrhea, vomiting, and constipation; a larger heart rate rise than GLP-1 only drugs, attributed to glucagon receptor activity; skin sensitivity and dysesthesia reported; long-term safety not established.
Route and dosing [3] [7]	Subcutaneous injection once weekly; label starts at 2.5 mg with 2.5 mg steps every 4 weeks to 5, 10, or 15 mg maintenance.	Subcutaneous injection once weekly in trials only; phase 2 used 1, 4, 8, or 12 mg maintenance after a 2 or 4 mg start. No approved dose exists.
Typical cost [3] [8] [12]	Zepbound list price up to 1,086.37 USD per fill; manufacturer self-pay vials or KwikPen 299 to 699 USD per month by dose (checked 2026-09-22); as little as 25 USD with commercial coverage and a savings card.	No lawful price. Trial participants receive it free. Products sold online as retatrutide are unapproved and unverified.

Evidence grade and regulatory status

Pulled from each peptide’s own record, so it stays in step with the peptide pages.

Tirzepatide and Retatrutide: grade, status, and cost
Attribute	Tirzepatide	Retatrutide
Class	Dual GIP and GLP-1 receptor agonist (39 amino acid peptide, acylated for once weekly dosing)	Investigational triple agonist of the GIP, GLP-1, and glucagon receptors (single acylated peptide, once weekly)
What it is	FDA approved weekly GIP and GLP-1 drug with 20.9% average weight loss at 15 mg in a 72 week randomized trial; beat semaglutide head to head.	Investigational triple agonist, nicknamed reta or GLP-3, with 24.2% weight loss at 48 weeks in phase 2 and 28.3% in a phase 3 topline; not FDA approved.
Evidence	Evidence: Human RCT evidence	Evidence: Human RCT evidence
FDA status	Regulatory: FDA approved	Regulatory: Not eligible for compounding
Compounding	FDA approved products (Mounjaro May 2022, Zepbound November 2023). FDA declared the tirzepatide shortage resolved on December 19, 2024; compounding by 503A pharmacies had to stop by February 18, 2025 and by 503B outsourcing facilities by March 19, 2025, except for a documented patient specific clinical need. FDA has warned about unapproved compounded and counterfeit tirzepatide products. On April 30, 2026 FDA proposed not to include tirzepatide on the 503B bulks list; that proposal was not final as of September 2026. Adding a vitamin such as B12 or niacinamide does not by itself make a compounded GLP-1 different from the approved drug. Under FDA's April 1, 2026 policy update, such a combination may be treated as essentially a copy when the strengths are within 10% of approved products and the route is the same, unless a prescriber documents a real difference for the individual patient. A September 2026 FDA warning letter applied this to semaglutide and tirzepatide vitamin combinations, said high production volume suggested the claimed differences were a pretext, and questioned significant-difference statements picked from preset menus on prescribing platforms.	Not FDA approved and not approved by any other regulator as of the last verification date. Because retatrutide is not a component of an approved drug, has no USP monograph, and is not on the 503A bulks list, it cannot lawfully be compounded by 503A pharmacies or 503B outsourcing facilities. FDA has warned that unapproved GLP-1 class products sold online, including investigational molecules, are not evaluated for safety, quality, or dose. Any product sold as retatrutide outside a clinical trial is unlawful for human use.
WADA	WADA: Not WADA prohibited	WADA: WADA prohibited
Routes	Subcutaneous injection once weekly (pen or single dose vial)	Subcutaneous injection once weekly (clinical trials only)
Typical cost	Manufacturer list price is up to 1,086.37 USD per fill for Zepbound and 1,112.16 USD for Mounjaro (checked 2026-09-22). Manufacturer self-pay Zepbound vials and KwikPen cost 299 USD per month at 2.5 mg, 399 at 5 mg, 499 at 7.5 mg, and 699 at 10 mg and above, with a 449 USD on-time refill offer for the 7.5 mg and higher KwikPen through 2026. With commercial insurance a savings card can bring a covered prescription to 25 USD, and eligible Medicare Part D enrollees pay 50 USD per month for the Zepbound KwikPen under the Medicare GLP-1 Bridge (July 2026 to December 2027). A study published in 2025 found compounded tirzepatide advertised at a median 330 USD for the first month during the shortage; compounding is now limited to patient specific needs.	Not available through licensed channels. Products sold as research chemicals are not lawful for human use and are not verified for identity or purity.
Last verified	Sep 27, 2026	Sep 23, 2026

Has tirzepatide been tested directly against retatrutide?

No published trial has compared tirzepatide and retatrutide directly. The dimensions above come from separate studies and labels, and cross-trial comparisons are less reliable than a direct trial.

What do tirzepatide and retatrutide cost?

Typical cost of Tirzepatide and Retatrutide
Dimension	Tirzepatide	Retatrutide
Typical cost	$275 to $1,112 per month	Not available through licensed channels. Products sold as research chemicals are not lawful for human use and are not verified for identity or purity.
Price detail	Tirzepatide price by channel	Retatrutide price by channel

Where a price index exists, the range is the cash price per month across branded, compounded, and telehealth channels, without insurance. The cost pages give each channel separately with its sources. Otherwise the typical cost from the peptide record is shown. Legal access depends on your state: see peptide legality by state.

Frequently asked questions

Retatrutide vs tirzepatide: which causes more weight loss?

In separate trials, yes: retatrutide 12 mg produced 24.2% weight loss at 48 weeks versus tirzepatide 15 mg at 20.9% over 72 weeks. But the retatrutide trial had 338 participants and the tirzepatide trial 2,539, and they were not compared directly, so the size of the true difference is unknown until phase 3 results are in. [1] [3]

Can I get retatrutide instead of Zepbound or Mounjaro?

Not lawfully, outside a clinical trial. Retatrutide is not approved anywhere, is not on any FDA compounding list, and cannot be compounded. Tirzepatide is available by prescription as Mounjaro or Zepbound. Anything sold online as retatrutide is an unapproved drug with no verification of identity or dose. [7] [8] [9]

Is either banned for athletes?

Retatrutide is. Because it has no approval from any health authority, it falls under WADA section S0 and is prohibited at all times. Tirzepatide, as an approved GLP-1 based drug, is not on the Prohibited List. [10]

What is the difference in how they work?

Tirzepatide activates the GIP and GLP-1 receptors. Retatrutide activates those two plus the glucagon receptor, which increases energy expenditure and liver fat burning and is thought to explain the extra weight loss, at the cost of a bigger rise in heart rate. [3] [7]

Which has better safety data?

Tirzepatide, by far. It has been through FDA review, has thousands of trial participants, and has an approved label with defined warnings. Retatrutide's safety is known only from trials of a few hundred people over about one year, with no cardiovascular outcomes trial reported. [1] [3] [7]

Conditions studied

From the blog

Compounded tirzepatide in 2026: legality, cost, and safety
The tirzepatide shortage ended in December 2024 and routine compounded copies ended in 2025. What is still lawful, what it cost, FDA safety warnings, and how to check a pharmacy.
How to get retatrutide: clinical trials, expanded access, and the law
Retatrutide is not approved, so a clinical trial is the only lawful way to get it. How to search ClinicalTrials.gov, how expanded access works, and why online and compounded sources are unlawful.
Peptides for weight loss, ranked by human evidence
Tirzepatide, semaglutide, and liraglutide lead on human trials. Retatrutide is trial-only, and AOD-9604 and 5-amino-1MQ are animal-only. Ranking, legal status, and dated prices.
Retatrutide before and after: weight loss by dose and week in the trials
What retatrutide trials measured: 24.2% mean weight loss at 48 weeks in phase 2, up to 28.3% at 80 weeks in phase 3, and what happened to fat, waist size, and blood sugar.
Retatrutide benefits beyond weight loss: liver fat, blood sugar, and blood pressure
What retatrutide trials measured besides weight: liver fat, HbA1c, blood pressure, lipids, fat mass, and knee pain. What is proven, what is post hoc, and what is still unknown.
Retatrutide side effects: what the trials reported, dose by dose
Nausea, diarrhea, dysesthesia, heart rate, and dropouts in the retatrutide trials, with placebo rates. What the data say about safety, and what is still unknown.

Sources

Numbered citations above point to these primary sources. PubMed entries link to the indexed abstract.

Cite this page

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APA style: PeptideAgent. (2026, September 23). Tirzepatide vs retatrutide: evidence, cost, and legality. https://peptideagent.ai/compare/tirzepatide-vs-retatrutide
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Retatrutide vs tirzepatide (Zepbound, Mounjaro)

The short answer