Why Patients Left Approved Obesity Drugs for Gray-Market Retatrutide
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- Patients are using a weight-loss drug that has no approved version in the United States and no legal route through any pharmacy.
- The preprint found that most gray-market users had no record of an approved obesity drug before starting, and that among those who did, most had been on an Eli Lilly medicine.
- Many had been taking an FDA-approved obesity medicine first, and left it because it was too expensive, not working well enough, or hard to tolerate.
- Those who switched lost far less weight than trial participants, while still showing a measurable rise in heart rate.
- None of this use appears in prescription or insurance records, so clinicians only learn about it when a patient volunteers it.
Table of Contents
- What Retatrutide Is and Why No Pharmacy Can Legally Sell It
- How the Study Saw Patients That Claims Data Could Not
- Gray-Market Retatrutide Delivered Under Half the Weight Loss
- Why the Patients Who Switched Left an Approved Drug
- Research Gap
- Closing Thoughts
Patients across the United States are injecting a weight-loss drug that no company is licensed to sell and no pharmacy may lawfully compound.
A preprint study identified 652 patients whose clinical notes confirmed use of purported retatrutide, an investigational triple-hormone-receptor agonist from Eli Lilly that the Food and Drug Administration has not approved for any use.
Gray-market users lost 7.2% of body weight, under half the 15.5% recorded in retatrutide trial participants over the same window [1].
Quick Take & Core Data:
- Direct-to-consumer users lost an average of 7.2% of body weight at 6 to 12 months, against 15.5% among retatrutide clinical-trial participants (P=0.004) and 7.7% among matched tirzepatide users.
- Of 531 patients with a documented source, 378 (71.2%) obtained the product outside a clinical trial. New users grew 1.8-fold per quarter, reaching 228 in the first quarter of 2026 [1].
- Pooling both retatrutide cohorts, new-onset tachycardia was 2.88 times more frequent than among matched tirzepatide users (95% CI 1.68-4.85; P<0.001) [1].
- Lilly reported average weight loss of 28.3% at 80 weeks in TRIUMPH-1 [5].
What Retatrutide Is and Why No Pharmacy Can Legally Sell It
Retatrutide activates three metabolic receptors at once: glucose-dependent insulinotropic polypeptide, glucagon-like peptide-1, and glucagon. Approved incretin drugs hit one or two of those targets.
In TRIUMPH-1, the 12 mg group lost an average of 28.3% of body weight at 80 weeks, with 45.3% losing at least 30%, a level the company tied to bariatric surgery [5]. Lilly plans to file for approval in the first quarter of 2027, which puts a licensed version a year or more away [6].
There is no legal way to buy it. In a March 31, 2025 letter to the National Association of Boards of Pharmacy, the FDA‘s Division of Compounding II told every state board that retatrutide has no United States Pharmacopeia monograph, is not a component of any approved drug, and appears on neither the 503A nor the 503B bulk substances list, so compounded retatrutide qualifies for the exemptions under neither section [2]. The agency added that consumers should not buy such products, which are “of unknown quality and may be harmful to their health.”
The study recorded where patients said they got it. Of 531 patients with a documented source, 378 (71.2%) reported obtaining purported retatrutide outside a clinical trial: 217 (57.4%) through online or telehealth vendors, 111 (29.4%) through compounding pharmacies, and 33 (8.7%) through wellness clinics or medical spas [1]. Nearly a third used a channel the FDA had already told regulators has no lawful pathway for this molecule, and the number of new users grew 1.8-fold per quarter, reaching 228 in the first quarter of 2026 [1].
Sellers have drawn action too. The FDA’s December 10, 2024 warning letter to Summit Research Peptides calls the firm’s retatrutide products unapproved new drugs sold in violation of federal law [4]. The agency has warned separately about peptides labeled for research use that reach consumers with dosing instructions attached [3].
How the Study Saw Patients That Claims Data Could Not
Standard drug safety monitoring reads prescription records and insurance claims. An unapproved candidate produces neither.
“Unapproved drug candidates like retatrutide do not yet have a National Drug Code, and there is no FDA-approved retatrutide product that doctors can prescribe or pharmacies can dispense,” Venky Soundararajan, PhD, founder and chief scientific officer at nference, the health data company that ran the study and sells the clinical-data analysis software it used, said in written responses provided to LA Times Studios in September 2026.
The preprint describes using large language models to pull retatrutide mentions out of clinical free text, then having physician specialists sort real use from patients who only considered the drug, declined it, or described someone else’s experience [1]. nference reported that a clinician’s review of 320 sampled extractions found 99.8% prevalence-weighted accuracy for whether the patient used retatrutide and 90.3% for the supply route [1].
The same gap exists inside the medical record. “Major EHR platforms such as Epic and Oracle Health’s Cerner had no structured way for clinicians to record this gray-market use,” Soundararajan said, arguing both vendors should add fields for the reported product, vendor and dose.
That gap matters because the patient is usually the one who opens the subject. In 67% of 260 direct-to-consumer cases, the patient raised retatrutide first.
Gray-Market Retatrutide Delivered Under Half the Weight Loss
The study’s trial comparator is not TRIUMPH-1. It is the record of patients whose notes identified them as enrolled in a retatrutide trial, read over the same window as the gray-market users, and it includes an unknown number who received placebo [1]. At 6 to 12 months, direct-to-consumer users had lost a mean of 7.2% of body weight, against 15.5% among retatrutide clinical-trial participants over the same window (P=0.004), and close to the 7.7% recorded among matched tirzepatide users [1].
Heart rate rose in both retatrutide groups while weight loss lagged the trial. Mean heart rate rose 2.5 beats per minute at three months among direct-to-consumer users (P=0.011) and 4.3 beats per minute among trial participants (P=0.028), while changing 0.0 beats per minute among matched semaglutide users and 0.1 among matched tirzepatide users.
“This pattern suggests that at least some patients received a biologically active product capable of producing incretin-like cardiovascular pharmacology, but without the degree of weight-loss efficacy observed under a clinical-trial protocol,” Soundararajan said.
The symptom data showed the same pattern. Pooling both retatrutide cohorts, new-onset tachycardia was more frequent than among matched semaglutide users (RR 1.90; 95% CI 1.13-3.09; P=0.010) and matched tirzepatide users (RR 2.88; 95% CI 1.68-4.85; P<0.001), while benign control findings did not rise significantly. Major adverse cardiovascular events stayed uncommon, with wide confidence intervals.
Notes also described the product combined with cagrilintide, high-dose tirzepatide, BPC-157, NAD+ and insulin-like growth-factor analogues, none evaluated together in a trial. The authors report invented names such as “GLP-3” and “triple-G” on some preparations, which they say carry no established pharmacologic meaning. No vial was chemically tested.
Why the Patients Who Switched Left an Approved Drug
Most gray-market users were not switching from anything the record could see. Of 377 direct-to-consumer users, 250 (66.3%) had no structured semaglutide or tirzepatide record before they started [1].
Among the 127 who did, most had been on a Lilly drug. Tirzepatide, sold as Zepbound and Mounjaro, was the last agent for 82 (64.6%), and semaglutide, sold as Wegovy and Ozempic, for 45 (35.4%), so the documented switching ran mostly from an approved Lilly medicine to a purported version of Lilly’s unapproved successor to it [1]. The authors checked only those two drugs, so an absent record does not prove a patient was new to incretins.
Among 83 patients who gave a reason, 31 (37.3%) reported an inadequate response to their approved drug, ahead of the 27 (32.5%) who reported cost or loss of access and the 25 (30.1%) who reported intolerance.
Soundararajan reads that as system failure. “The current evidence suggests failures in the affordability and access of existing medicines (Zepbound, Mounjaro), a lack of online accountability among gray-market peptide sellers, and the inability of existing EHR vendors to provide clinicians with a structured entry mechanism for unapproved drugs that could potentially harm or help patients,” he said.
For clinicians the consequence is narrow. Where a patient discloses gray-market use, heart rate is worth monitoring, and that disclosure is the only record there is. Getting it, Soundararajan said, means patients “need clear, nonjudgmental, evidence-based information and a safe way to disclose exactly what they used, where it came from, what dose they believed they received, and what other substances may have been included.”
Research Gap
The study is observational and cannot establish cause. Its central limitation is timing: follow-up ran a median of roughly three months in the retatrutide groups against six months in the comparators, and index dates came from what patients told clinicians rather than from dispensing records [1].
The authors go further and say which way that cuts. A patient discloses gray-market use at whatever visit happens to follow starting it, so the true start almost always precedes the first note, and the steepest early weight loss goes unrecorded. On the authors’ own account the direct-to-consumer figure understates that group’s real weight loss, and the gap against the trial cohort is overstated [1].
The identity, purity, concentration and dose of what these patients injected remain unknown, and the reported dose is a patient’s recollection.
A separate nference analysis offers one way to read that gap. Patients kept on the lowest labeled starting doses of semaglutide and tirzepatide, rather than escalated toward the maintenance dose, lost 2.2% and 5.5% of body weight at 12 months, against roughly 12% for patients who escalated [7]. Gray-market retatrutide’s 7.2% sits in that low-dose range rather than a full therapeutic one, which raises the possibility that some purported product was underdosed rather than inert.
This study cannot confirm it. The dose reported here is unverified.
The supply route is likewise a patient’s account in a note, at 90.3% pipeline accuracy. Those accuracy figures come from nference’s own clinician review of its own output rather than outside validation.
Major adverse cardiovascular events were too infrequent for the confidence intervals to say much, leaving the question of cardiac risk to prospective trials with longer follow-up.
Closing Thoughts
A licensed version of retatrutide is a year or more away at best, and the use documented here is still growing.
The record shows patients buying an unapproved copy of a drug whose trial results they read about, paying out of pocket, accepting unverified contents, and getting roughly what the approved drug they left was already giving them. Decisions about obesity treatment belong with a reader’s own clinician rather than an online seller.
References
1. Murugadoss, K., Venkatakrishnan, A. J., & Soundararajan, V. (2026, August 18). Accelerating use of unapproved retatrutide is associated with weaker weight loss and increased cardiovascular symptoms [Preprint]. Preprints.org. https://doi.org/10.20944/preprints202608.1193.v1
2. Gozun, E. (2025, March 31). Letter to the National Association of Boards of Pharmacy regarding retatrutide in compounded drug products. U.S. Food and Drug Administration, Office of Compounding Quality and Compliance. https://www.pharmacy.ohio.gov/documents/pubs/special/compounding/fda%20letter%20-%20retatrutide%20in%20compounded%20drug%20products.pdf
3. U.S. Food and Drug Administration. (2026, September 1). FDA’s concerns with unapproved GLP-1 drugs used for weight loss. https://www.fda.gov/drugs/drug-alerts-and-statements/fdas-concerns-unapproved-glp-1-drugs-used-weight-loss
4. U.S. Food and Drug Administration. (2024, December 10). Warning letter: Summit Research Peptides (695607). https://www.fda.gov/inspections-compliance-enforcement-and-criminal-investigations/warning-letters/summit-research-peptides-695607-12102024
5. Eli Lilly and Company. (2026, May 21). Lilly’s triple agonist, retatrutide, delivered powerful weight loss in pivotal Phase 3 obesity trial [Press release]. https://investor.lilly.com/news-releases/news-release-details/lillys-triple-agonist-retatrutide-delivered-powerful-weight-loss
6. Larkin, M. (2026, August 26). Gray-market retatrutide: Less weight loss, more CV effects. Medscape. https://www.medscape.com/viewarticle/gray-market-retatrutide-less-weight-loss-more-cv-effects-2026a1000tpl
7. Murugadoss, K., Venkatakrishnan, A. J., & Soundararajan, V. (2026, August 31). Comparison of cardiometabolic benefits and tolerability in patients on sustained low doses of semaglutide or tirzepatide. Biology Methods and Protocols, bpag048. https://doi.org/10.1093/biomethods/bpag048
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