- Prescription peptide noun
- A medicine that needs a prescription.
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In use
Promise Peptides prescribes compounded tirzepatide at mypromise.com; it does not offer investigational retatrutide.
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A licensed U.S. clinician checks each request, then accepts or declines it. Only U.S. patients may request care, and every treatment has state limits. The compounded form has no FDA approval; FDA-approved tirzepatide exists.
The short answer · LY3437943
What did the Phase 3 Retatrutide study find?
People lost a lot of weight on average. You still face the catch: Retatrutide isn’t approved, and Phase 1, Phase 2, and Phase 3 left long-term safety questions open.
What is Retatrutide, and can you get it?
Retatrutide comes from a lab. Its study name is LY3437943, and it mimics three gut hormones tied to hunger, blood sugar, and the way you burn fuel [6].
The drug is a linked row of protein building blocks, each marked by a number. At the place marked 17, scientists added fat so it could ride on a blood protein and remain about 6 days while your kidneys cleared it more slowly from your blood [5][14].
Your body doesn’t make Retatrutide. It copies GLP-1 and two other hormones, while Eli Lilly and Company of Indianapolis, Indiana, US, made and named LY3437943 [14].
Eli Lilly runs TRIUMPH Phase 3 after earlier Phase 1 work. Retatrutide has no FDA-approved use; registered trials provide supervised access, while routine prescriptions cannot supply it [21]. Material labelled for research is still sold, but it is not approved for human use.
The first large result came in May 2026. In TRIUMPH-1, the 12 mg group lost 28.3% on average over 80 weeks, but you might lose more or less [9].
What changes did Retatrutide cause in people?
Retatrutide may curb your hunger and slow your stomach. GLP-1 is one of its three copied hormones, while 2 others may help insulin and fuel use [6].
GLP-1 can slow your stomach. Its GLP-1 effect joins two more hormone effects that may change what you feel [12].
The Phase 2 weight study was small and lasted 48 weeks. At 12 mg, average loss was 24.2% versus 2.1% with placebo, which held no medicine; 83% lost at least 15% [1].
Phase 3 was larger: TRIUMPH-1 followed 2,339 people for 80 weeks. With 12 mg, average loss was 28.3%, and 45.3% lost at least 30% [9].
The Phase 2 diabetes study was shorter, with 281 people over 36 weeks. At the top amounts, loss reached 16.9%, and 82% reached a usual-blood-sugar reading of 6.5% or less [4].
The liver study was small and ran 24 weeks. With 12 mg, liver fat fell 82.4%, so it can’t tell you whether the change would last [7].
Which health problems are Retatrutide studies checking?
Most studies ask how much weight people lose. Adults qualified with a body mass index of 30 or more, or 27 or more plus a weight-linked illness; the index uses weight and height [21].
Other work covers type 2 diabetes, fatty liver, heart disease, and kidney health. None of those findings makes Retatrutide approved care.
Phase 3 TRIUMPH-1 followed 2,339 adults with obesity for 80 weeks [9]. TRIUMPH-4 ran 68 weeks; at 12 mg, weight fell 28.7% and knee pain scores fell 75.8% [10].
TRIUMPH-3 still follows adults with both obesity and heart disease [21]. Another study checks heart and kidney health, so those answers aren’t ready.
The cancer clue is weak because it came only from mice. Mice given Retatrutide had smaller pancreas and lung tumors than untreated mice, and 50% with lung tumors cleared them [8].
The mice’s immune systems kept fighting tumors after the drug stopped, though their weight returned. A human study hasn’t found that, so this work says nothing firm about your cancer care.
See Retatrutide dosage in clinical research for study amounts. See Retatrutide side effects for problems reported in Phase 2 and Phase 3.
Is Retatrutide natural, and what does GLP-3 mean?
No. Retatrutide comes from a lab, with a fat link that helps it copy three hormones from your gut [14].
One of those hormones is called GLP-1. GLP-3 is only an informal nickname for Retatrutide, not a medical drug class.
Calling it GLP-3 doesn’t change the drug. Papers may use more lab shorthand, but those labels won’t help you judge the results [14].
Tests in cells in a dish found changes linked to all three hormones. Those tests can’t show what share of an effect you would get from each hormone [14].
Who made Retatrutide, and what must happen next?
Eli Lilly and Company of Indianapolis, Indiana, US, made Retatrutide and named it LY3437943. The company also runs the TRIUMPH Phase 3 studies.
The May 2026 TRIUMPH-1 result did not grant FDA approval for prescription use [21]. There is no settled date for Retatrutide to enter routine prescription care.
Read how the three hormone effects work for the body changes. You’ll also find the Phase 2 and Phase 3 results and plain Retatrutide answers.