Comparison
Retatrutide vs tirzepatide: how does the investigational triple agonist compare?
Tirzepatide (Zepbound, Mounjaro) is FDA-approved and acts on two hormone receptors, GIP and GLP-1. Retatrutide adds a third, glucagon, and is not approved: FDA says it cannot be compounded and has not been found safe and effective. No head-to-head result has been published; Lilly’s TRIUMPH-5 trial comparing them lists its primary completion as November 2026.
How do Retatrutide and Tirzepatide compare?
| Attribute | Retatrutide | Tirzepatide |
|---|---|---|
| Regulatory status | Research only · Not for human use | FDA-approved · Prescription |
| Human evidence | Emerging evidence | Strong human evidence |
| Comes as | Weekly injection (in trials) | Weekly injection |
| How you get it | Not lawfully available for personal use. DiscoverMedica links to no seller. | A prescription from a licensed clinician, filled by a licensed pharmacy. 22 providers are listed on DiscoverMedica. |
| How it worksNEJM 2023Zepbound label | Activates the GIP, GLP-1 and glucagon receptors | Activates the GIP and GLP-1 receptors |
| FDA positionFDAZepbound labelMounjaro label | Investigational; FDA says it cannot be used in compounding and has not been found safe and effective | Approved as Zepbound (weight, sleep apnea) and Mounjaro (type 2 diabetes) |
| Obesity without diabetesNEJM 2023SURMOUNT-1 | Phase 2: about 24% average loss at 48 weeks in the highest-dose group, versus about 2% on placebo | SURMOUNT-1: about 15% to 21% average loss at 72 weeks across its three treatment groups, versus about 3% on placebo |
| Obesity with type 2 diabetesTRIUMPH-2Mounjaro label | TRIUMPH-2 (phase 3): about 12% to 19% average loss at 80 weeks across groups, versus about 5% on placebo | Approved for type 2 diabetes as Mounjaro |
| Head-to-head trialClinicalTrials.gov | TRIUMPH-5: about 800 adults with obesity, weight change measured at 80 weeks; not reported as of October 2026 | The comparator in the same trial |
| Key risksNEJM 2023TRIUMPH-2FDAZepbound label | Digestive side effects were the most common in trials, and heart rate rose in the phase 2 trial, peaking at 24 weeks. It has no FDA label. Products sold online as research chemicals are not the trial drug and may be counterfeit or contaminated. | Boxed warning for thyroid C-cell tumors in rodents. GI side effects are common. Label warnings include pancreatitis, gallbladder problems and kidney injury. It can make birth control pills less reliable for a period after starting and after each step up in treatment. |
| Listed prices | No lawful seller, so no price is listed. | Listed starting prices run from $90 to $791 across 14 providers, checked October 7, 2026. |
Status, evidence, formats, routes and prices come from each compound’s page. Prices are the providers’ own listed starting prices, which may exclude a membership fee and change often; they are not DiscoverMedica’s prices.
Does retatrutide lead to more weight loss than tirzepatide?
That is unknown, because no trial comparing them directly has reported. TRIUMPH-5, a phase 3 trial of about 800 adults with obesity, randomly assigns people to retatrutide or tirzepatide and measures weight change at 80 weeks. ClinicalTrials.gov lists its primary completion as November 2026. ClinicalTrials.gov
In retatrutide’s phase 2 trial of 338 adults with obesity, average weight loss at 48 weeks reached about 24% in the highest-dose group, versus about 2% on placebo. NEJM 2023
In SURMOUNT-1, tirzepatide participants lost about 15% to 21% on average over 72 weeks, depending on treatment group. Separate trials enrolled different people for different lengths of time, so their numbers cannot be compared side by side. SURMOUNT-1
How do retatrutide and tirzepatide work differently?
Tirzepatide is a single molecule that activates two gut-hormone receptors, GIP and GLP-1, which act on appetite and help the pancreas release insulin when blood sugar is high. Retatrutide activates those two plus the glucagon receptor, which is why it is called a triple-hormone-receptor agonist. NEJM 2023
Is retatrutide FDA-approved like tirzepatide?
No. Tirzepatide is approved as Zepbound and Mounjaro. FDA says retatrutide cannot be used in compounding under federal law, is not a component of any FDA-approved drug, and has not been found safe and effective for any condition. FDA has also acted against companies selling it labeled “for research purposes” or “not for human consumption”. FDA
The phase 3 program is reporting. In TRIUMPH-2, adults with obesity and type 2 diabetes lost about 12% to 19% of body weight on average at 80 weeks across retatrutide groups, versus about 5% on placebo. TRIUMPH-2
Do retatrutide and tirzepatide have different side effects?
Both mostly cause digestive side effects. In TRIUMPH-2, diarrhea affected about 27% to 34% of people on retatrutide versus 13% on placebo, and nausea 14% to 28% versus 8%. Stopping because of side effects ranged from 4% to 12% across retatrutide groups, versus 5% on placebo. TRIUMPH-2
In the phase 2 trial, heart rate rose on retatrutide, peaking at 24 weeks and then declining. NEJM 2023
Tirzepatide’s risks are set out in its FDA label, including the boxed warning about thyroid C-cell tumors in rodents. Zepbound label
Which might suit whom: Retatrutide or Tirzepatide?
Only one of these can be prescribed today. These questions help with the decision you can actually make:
- Is tirzepatide, or another approved medication, a reasonable option for my weight and health goals?
- Is there a retatrutide clinical trial I might qualify for?
- Given my history of pancreatitis, gallbladder disease or heart rhythm problems, is this class of medication a poor fit?
- Which approved option does my insurance cover?
- If I have seen retatrutide sold online, what are the risks of an unverified product?
DiscoverMedica does not recommend one over the other. Only a licensed clinician who knows your history can decide.
Start My Journal with these.
Adds Tirzepatide to My Journal, with the questions to ask a clinician. It stays in this browser, and nothing on it is a commitment.
Where to get each
Licensed providers that list each one on DiscoverMedica, by name. The full list is on each compound’s page.
Prices as listed by the provider when we checked; they change.
Retatrutide vs Tirzepatide: questions, answered
Is retatrutide stronger than tirzepatide?
There is no direct answer. Retatrutide’s trials reported large average weight losses, but no trial comparing it with tirzepatide has reported. TRIUMPH-5, the head-to-head phase 3 trial, measures weight change at 80 weeks, with primary completion listed for November 2026. Comparing numbers across separate trials is unreliable because the people and durations differ.
Can I use retatrutide instead of tirzepatide?
Not lawfully outside a clinical trial. Retatrutide is not FDA-approved, and FDA says it cannot be used in compounding. Products sold online as research chemicals are not the trial drug and are not made to drug standards, so identity, purity and sterility are unverified. Tirzepatide is available by prescription as Zepbound or Mounjaro.
Is retatrutide a GLP-1 like tirzepatide?
Partly. Retatrutide activates the GLP-1 receptor, like semaglutide and tirzepatide, and also the GIP and glucagon receptors, which is why it is called a triple agonist. Tirzepatide activates GIP and GLP-1. The Zepbound label advises against using tirzepatide together with any other GLP-1 medication.
What does tirzepatide cost?
Tirzepatide: Listed starting prices run from $90 to $791 across 14 providers, checked October 7, 2026. Retatrutide has no lawful retail price because it is not approved. Listed prices change often, and insurance coverage changes the real cost.
Sources
- Triple-hormone-receptor agonist retatrutide for obesity: a phase 2 trial (NEJM 2023)
- TRIUMPH-2: Retatrutide in adults with obesity and type 2 diabetes, phase 3 (Lancet 2026)
- ClinicalTrials.gov: TRIUMPH-5, retatrutide compared with tirzepatide in adults with obesity (NCT06662383)
- SURMOUNT-1: Tirzepatide once weekly for the treatment of obesity (NEJM 2022)
- DailyMed: Zepbound prescribing information
- DailyMed: Mounjaro (tirzepatide) prescribing information, revised August 2026
- FDA: Concerns with unapproved GLP-1 drugs used for weight loss
- ClinicalTrials.gov: TRIUMPH-1 (NCT05929066)
- FDA (Apr 30, 2026): Proposal to exclude semaglutide, tirzepatide and liraglutide from the 503B bulks list
Last reviewed October 7, 2026. Every source above was checked on or before that date. Educational information only, not medical advice; it does not replace a conversation with a licensed clinician. DiscoverMedica does not employ clinicians.