Unregulated Peptides Lack Purity Testing: Catherine Varney, DO

Gray market peptides frequently contain far less of the active ingredient than their labels claim, and some carry toxic impurities such as arsenic at up to 10 times acceptable levels, according to Catherine Varney, DO, obesity medicine director at UVA Health. As peptide products are injected, she warned, the stakes are higher compared with contaminated foods that are swallowed.

Rapid Growth After FDA Approvals

The unapproved market existed before, but it has exploded since FDA-approved peptides became widely used around 2021, Varney said. Patients who see the benefits of approved medications but cannot afford them are turning to gray market and direct-to-consumer sellers, a market some projections place at $50 billion to $75 billion by 2028.

Social media has aggressively promoted these products as an alternative to FDA-approved therapies. Approved peptides such as liraglutide (Victoza, Saxenda), semaglutide (Ozempic, Wegovy), and tirzepatide (Mounjaro, Zepbound) went through preclinical, animal, and human studies, and glucagon-like peptide-1 (GLP-1) agents have been used for more than 20 years.

"But these gray market products are not established to be safe or effective in humans," she said.

Evidence Rests Largely on Animal Studies

Varney cited a scoping review in the American Journal of Sports Medicine that found 67% of peptide publications were preclinical, mostly in rats, with promising but variable results.¹ The few human studies were largely uncontrolled and showed modest benefits at best. Broadly, only about 5% of animal-tested interventions ever reach regulatory approval, she noted, so patients are acting on evidence that may not translate to humans. Some of her patients report feeling better on these products, but the long-term risks remain unknown.

Purity Testing Falls to Patients

One of Varney's patients belongs to a group that pools money to send gray-market peptides for third-party purity testing, but she said that is rare and requires high health literacy and resources. Otherwise, no one tests these products before they reach patients. Analyses have found that peptides often contain only 5% to 75% of the labeled amount, far from the 99% to 100% purity expected of a medication.

"So really the quality assurance falls entirely on these unregulated suppliers," she said.

Reference

1. Tewari K, Liu TP, Im C, et al. Peptide supplements and their therapeutic applications in sports medicine. Am J Sports Med. Published online August 11, 2026. doi:10.1177/03635465261464420