Retatrutide in Costa Rica: what it is, what is known, and why the lab report matters
· Novatheris
Retatrutide is the most talked-about peptide in metabolic research, and also the one with the least published data of the three in its group. If you are looking for retatrutide in Costa Rica, it pays to know both things before buying a vial.
Here is what the studies say, what they do not say yet, and a 2026 finding that explains why we require a lab report for every batch.
What retatrutide is
Retatrutide is a single peptide that activates three receptors at once: GIP, GLP-1 and glucagon. That is why it is called a triple agonist.
The first two are gut hormones released after a meal. The third, glucagon, comes from the pancreas. According to the studies, the glucagon arm adds increased energy expenditure to the effect the other two have on appetite.
Today retatrutide does not exist as a commercial medicine in any country. It is still in clinical trials, and its phase 3 obesity programme has not published results yet.
The chemistry
It is the shortest fact sheet in its group, because the molecule is new:
- Molecular weight: 4730.477 Da.
- CAS: 2381089-83-2.
- Formula and full sequence: not included in our fact sheet, because we found no published source we can cite.
- Half-life in humans: no published numeric value. In the phase 1 single-dose study, the blood profile was compatible with action lasting several days, and body weight was still reduced on day 43 after a single dose.
- Half-life in animals: no published data found.
That phase 1 study is the discovery paper, from when the molecule was still called LY3437943: Coskun et al., Cell Metab 2022.
What the published studies measured
There are three clinical trials with published results.
Phase 2 in obesity. 338 adults with obesity or overweight, over 48 weeks. Mean weight change at 48 weeks was -8.7 %, -17.1 %, -22.8 % and -24.2 % depending on dose, versus -2.1 % with placebo. It is in Jastreboff et al., N Engl J Med 2023.
Phase 2 in type 2 diabetes. 281 adults with type 2 diabetes, compared with placebo and with dulaglutide. The primary endpoint was measured at 24 weeks and secondary endpoints at 36. It is in Rosenstock et al., Lancet 2023.
TRANSCEND-T2D-1, phase 3. 537 adults with type 2 diabetes not controlled by diet and exercise, over 40 weeks. Mean weight change was -11.5 %, -13.9 % and -15.3 % depending on dose, versus -2.6 % with placebo. It is in Bajaj et al., Lancet 2026.
These figures are group averages inside a medical protocol. They do not predict what happens in a single case and they are not a usage guide.
What is still unknown
Phase 3 in obesity is not published. The only published phase 3 trial is in type 2 diabetes and lasts 40 weeks. Everything known about retatrutide and obesity comes from a phase 2 trial with 338 people. The -24 % figures that circulate come from there, not from a confirmatory trial.
The heart over the long term. In the phase 2 obesity trial, heart rate rose with dose, peaked at 24 weeks and then declined. There is no published cardiovascular outcomes trial with retatrutide.
What happens on discontinuation. The published trials end with treatment still ongoing, with no follow-up period afterwards. There is no published data on what happens to weight once it is stopped.
Retatrutide in Costa Rica: the label problem
This is the finding that matters most to us as a seller.
In 2026, a group of researchers in Australia bought three products sold as retatrutide, all labeled 10 mg, and had them measured. All three contained the right peptide. But the amounts were 5.13 mg, 16.5 mg and 19.0 mg. One held half of what it claimed and another almost double. It is the work of Piatkowski et al., Drug Alcohol Rev 2026.
It is only three samples. But it shows something clear: when a product is sold without independent testing, the label does not tell you how much is inside.
For a research project, that is not a detail. If the real amount is half or double, every measurement you take starts from the wrong number.
What to check in the vial
Before using a retatrutide vial, check that it has a third-party lab report, that the report confirms the peptide's identity and purity, and that it belongs to the same batch and strength as the vial you hold.
At Novatheris we send every batch to Janoshik or Freedom Diagnostics and publish the full report. We require +99.5 % purity. The retatrutide report is on its lab report page.
Delivery takes 2 hours in the GAM (the Greater Metropolitan Area around San José) and 24 hours in the rest of Costa Rica.
How it is stored
As a powder, or lyophilized (freeze-dried), retatrutide is stored at -20 °C, where it is stable. Once reconstituted, 2 to 8 °C and only for the short term. Let the vial reach room temperature with the cap on before opening it, so no moisture gets in.
For research
The retatrutide we sell is a research reagent, not a medicine. We do not give doses or directions for use, and outside a clinical protocol there is no established dose.
The retatrutide page has the full fact sheet with every citation, and the lab report shows the lab's results. If you work with the three peptides together, see the retatrutide kit.