Tirzepatide is an FDA-approved weight management medication you can get with a prescription today. Retatrutide is an investigational drug that adds a third hormone target and is not approved in the United States. Early data make retatrutide interesting. Only tirzepatide has a full approval, a labeled dosing schedule and a safety record you can rely on.
This guide explains how the two differ, what trials report, how the side effects compare and what that means if you want doctor-led weight loss care now.
TL;DR
- Tirzepatide activates two receptors (GIP and GLP-1). Retatrutide activates three (GIP, GLP-1 and glucagon).
- The FDA approved tirzepatide for chronic weight management in 2023. Retatrutide has no FDA approval for any condition.
- A 2025 analysis found retatrutide produced greater weight reduction than tirzepatide in the trials analyzed, with more adverse events. The first head-to-head trial has not reported yet.
- The FDA says retatrutide cannot be used in compounding under federal law, so products sold as retatrutide are unapproved.
- If you want a prescription now, tirzepatide-based and other GLP-1 care under clinician supervision is the path that exists.
Table of Contents
- What retatrutide and tirzepatide are
- How the medications work
- Weight loss: what trials report
- Side effects and safety
- Dosing: labeled for one, experimental for the other
- Availability: what you can actually get
- Which one is right for you?
- Our perspective
- Start doctor-led GLP-1 care
- FAQ
- Sources
What retatrutide and tirzepatide are
Both medications are once-weekly injectables developed by Eli Lilly. Both belong to the family of incretin-based therapies, which act on gut hormones that regulate appetite, blood sugar and digestion.
Tirzepatide is marketed for weight management as Zepbound. It is a dual agonist. According to Lilly's medical information page, tirzepatide activates GIP and GLP-1 receptors.
Retatrutide is a synthetic molecule that Lilly describes as a triple agonist. It activates GIP, GLP-1 and glucagon receptors, as stated on that same Lilly page.
The practical difference is one extra target. Glucagon signaling is linked to energy expenditure, and that is why researchers expect a third receptor may add weight loss on top of what GIP and GLP-1 already do.
How the medications work
GLP-1 receptor activation reduces appetite, slows stomach emptying and helps you feel full sooner. GIP activation works alongside it on appetite and metabolic signaling. Tirzepatide combines the two in a single molecule.
Retatrutide keeps those two actions and adds glucagon receptor activity. If you want a closer look at retatrutide's three receptor targets, the mechanism is the reason it is often called a triple agonist rather than a "GLP-3," a label that does not describe a real drug class.
Here is the side-by-side view.
| Tirzepatide | Retatrutide | |
|---|---|---|
| Receptors targeted | GIP and GLP-1 | GIP, GLP-1 and glucagon |
| Type | Dual agonist | Triple agonist |
| FDA status for weight management | Approved in 2023 | Not approved |
| Labeled dosing | Yes, once weekly | None, trial dosing only |
| Available by prescription | Yes | No |
| Phase 3 head-to-head data | Comparator in TRIUMPH-5 | Under study in TRIUMPH-5 |
Weight loss: what trials report
Trial numbers are not a promise of your results. They do show what each drug can do under supervision.
Tirzepatide
In the SURMOUNT-1 trial, adults treated with tirzepatide for 72 weeks reached mean weight reductions of up to 20.9% on the 15 mg dose, compared with 3.1% on placebo, according to the New England Journal of Medicine. Doses were raised gradually over up to 20 weeks, so results build over months rather than appearing at once.
Retatrutide
A 2024 network meta-analysis of incretin-based drugs ranked retatrutide 12 mg, retatrutide 8 mg and tirzepatide 15 mg as the three most effective treatments for reducing body weight and waist circumference. That puts both drugs at the top of the field, with retatrutide at the highest doses leading.
A 2025 network meta-analysis reported that retatrutide showed greater absolute and percentage weight reduction than tirzepatide. It also found a higher frequency of adverse events in the trials analyzed.
How comparable are these results?
Not as comparable as the headlines suggest. A network meta-analysis compares drugs indirectly, across different trials with different participants, doses and durations. It is not a head-to-head study.
That study exists. Eli Lilly started a phase 3 trial, TRIUMPH-5, to directly compare retatrutide with tirzepatide. ClinicalTrials.gov lists an estimated primary completion date of November 2026. Check that page for the current status before relying on any claim about who wins.
Two more points help you read the numbers:
- Diabetes status matters. Systematic reviews through 2024 indicate that people with obesity and no type 2 diabetes generally lose more weight on these therapies than people with type 2 diabetes, according to the same 2024 review.
- Trials include structured support. A commentary in the Annals of Internal Medicine noted that placebo-controlled trials could overestimate effectiveness, and that lifestyle support inside a trial may not match what people get outside one.
The last point is why clinician oversight, nutrition guidance and coaching matter. The medication does part of the work. The support around it helps you keep the results.
How much weight per month on tirzepatide?
There is no fixed monthly figure. SURMOUNT-1 reported weight change at week 20 and week 72, and the dose was escalated over up to 20 weeks. Early weeks are usually slower because the dose is still low. Our guide to the tirzepatide results timeline explains why appetite often shifts before the scale does.
Side effects and safety
Both drugs act on the digestive system, so gastrointestinal effects such as nausea, diarrhea and constipation are the ones people most often ask about. Retatrutide's profile is still being defined. The 2025 analysis cited above found more adverse events with retatrutide in the trials it reviewed, which is a reason to wait for direct comparison data rather than assume the higher weight loss comes free.
If you take tirzepatide and have digestive symptoms, these guides cover practical steps:
- Tirzepatide diarrhea: home relief, dose changes and when to call
- Tirzepatide constipation: causes, relief and warning signs
Call your prescriber promptly if you have severe or persistent vomiting, severe abdominal pain or signs of dehydration. Do not change your dose on your own.
The risk of unapproved products
The FDA warns that unapproved versions of GLP-1 drugs do not go through agency review for safety, effectiveness or quality. It also says adverse events from compounded products are likely underreported, because they are not required to be submitted to the FDA.
That is a strong reason to get any GLP-1 medication through a licensed clinician and a pharmacy, and never from a website selling vials with no prescriber involved. Our overview of compounded tirzepatide safety covers what to check.
Dosing: labeled for one, experimental for the other
Tirzepatide has a defined schedule in its FDA label, revised in September 2025. Per the prescribing information, treatment starts at 2.5 mg once weekly for 4 weeks. The dose then rises in 2.5 mg steps after at least 4 weeks at the current dose. The same label lists maintenance doses for weight management of 5 mg, 10 mg or 15 mg injected subcutaneously once weekly.
The slow step-up exists to let your body adjust and to limit digestive side effects. Your prescriber decides the pace and the dose that fits you.
Retatrutide has no labeled dose. Doses you see quoted online come from trials in which participants were monitored, and they are not instructions. Anyone offering you a retatrutide dose to inject at home is guessing.
Availability: what you can actually get
This is the section most readers need.
The FDA approved tirzepatide for chronic weight management in adults with obesity, or overweight with at least one weight-related condition, in 2023. It is meant to be used with a reduced-calorie diet and more physical activity.
Retatrutide is a different story. The FDA says it cannot be used in compounding under federal law. It is not a component of an FDA-approved drug and has not been found safe and effective for any condition. The agency has warned companies marketing it. In one 2025 warning letter, the FDA said a company's compounded retatrutide products were unapproved new drugs that were not eligible for the exemptions in sections 503A or 503B.
In plain terms, a legitimate US clinician cannot prescribe retatrutide for weight loss today. Sites selling it directly are outside the approved system. Whatever the label says, you cannot verify what is in the vial.
If you are comparing costs for the drugs that are available, see our breakdown of US tirzepatide costs. For rule changes affecting compounded products, read the compounded tirzepatide availability update. If you wonder about other formats, we explain the status of oral tirzepatide and sublingual tirzepatide too.
Which one is right for you?
For most people the real choice is not tirzepatide or retatrutide. It is between approved, clinician-supervised options and unverified products. Use these criteria.
- Regulatory status. Approved drugs have been reviewed for safety, effectiveness and quality. Investigational drugs have not.
- Dosing guidance. A labeled titration schedule protects you from starting too high.
- Clinical oversight. A clinician should review your history, medications and conditions before prescribing, and follow up as you progress.
- Support. Nutrition guidance and coaching help you keep the weight off after the dose is stable.
- Cost clarity. Look for a total monthly price that includes clinical care, medication and shipping.
By those criteria, tirzepatide is the option you can use today. If retatrutide completes its trials and wins approval, the same criteria will tell you whether it belongs in your plan. A clinician will be able to prescribe it then, with a label, a dosing schedule and safety data.
Our perspective
We follow retatrutide closely, and the research is promising. A third receptor target is a real scientific step, and the head-to-head TRIUMPH-5 results will matter.
But weight loss care works when it is safe, supervised and sustainable. That means a medication that is available through proper channels, a clinician who knows your history and support that continues after the first month.
This is how we built our programs. You complete an online intake, a clinician reviews it, and if you are approved your medication ships to you. Dietitian visits are free and care coaching is included. There are no membership fees, pricing is transparent and cash-pay, and you can cancel flexibly. We offer injection, microdose and needle-free oral GLP-1 options so your plan fits how you want to treat.
We would rather you start with a medication that has clear guidance and real oversight than wait for a drug that is not yet available.
Flexible
Start doctor-led GLP-1 care
If you want to begin now, we offer personalized GLP-1 care with clinician evaluation, medication, coaching and shipping bundled into one monthly price. Published plans start at $179 per month for GLP-1 injection, $159 per month for GLP-1 microdose and $149 per month for oral GLP with liposomal delivery. The dayla GLP-1 program is $299 per month. Your clinician confirms which option suits you after your intake.
See the plans and current pricing, or read about tirzepatide at Dayla Health.
FAQ
Which is better, tirzepatide or retatrutide?
Retatrutide produced greater weight reduction than tirzepatide in a 2025 analysis of trials, but it also had more adverse events, and no direct comparison has been published. Tirzepatide is FDA-approved and prescribable. Retatrutide is not approved. For someone who wants treatment now, tirzepatide is the better choice.
Can I get retatrutide with a prescription in the US?
No. The FDA says retatrutide cannot be used in compounding under federal law and is not part of any approved drug. Products sold online as retatrutide are unapproved. You cannot confirm their quality or contents.
How much weight do you lose on tirzepatide per month?
It varies. In SURMOUNT-1, participants on the highest dose lost up to 20.9% of body weight over 72 weeks, with the dose raised gradually over up to 20 weeks. Early months usually bring smaller changes while the dose builds. Your clinician can set expectations based on your starting point.
Is retatrutide the same as a GLP-3?
No. Retatrutide targets GLP-1, GIP and glucagon receptors. "GLP-3" is a nickname, not a distinct hormone or drug class.
Sources
- What is the difference between the retatrutide and tirzepatide molecules? (Eli Lilly medical information)
- A Study of Retatrutide Compared to Tirzepatide (ClinicalTrials.gov)
- Tirzepatide Once Weekly for the Treatment of Obesity (NEJM)
- Seven glucagon-like peptide-1 receptor agonists and polyagonists network meta-analysis (PubMed)
- Comparative Efficacy and Safety of Tirzepatide vs Retatrutide (PMC)
- Efficacy and Safety of Glucagon-Like Peptide-1 Receptor Agonists (Annals of Internal Medicine)
- FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss
- FDA warning letter to GLP-1 Solution, 09/09/2025
- Zepbound prescribing information, revised 09/2025 (FDA)
- FDA Approves New Medication for Chronic Weight Management
- Retatrutide's 3 Targets Debunk "GLP-3" for Researchers