The Mr. Green bodega sits on a busy stretch of Bedford Avenue in Brooklyn, New York. Near the counter, you can buy the usual assortment of candy, gum, rolling papers, and soda. You can also purchase tiny vials of injectable peptides. So we did. And then we sent them to a lab.

Mr. Green is one of several shops that went viral this summer for selling peptides, a broad class of amino acids touted for their ability to aid in everything from weight loss to injury recovery. For $376.20, we acquired four varieties from a vendor called INDR Labs: PT-141, for low libido; BPC-157, for healing and muscle recovery; NAD+, for cellular repair; and retatrutide, for weight loss. The clerk packed them up in an unlabeled paper bag and sent us on our way.

WIRED sent the vials to Finnrick, an Austin-based startup that offers independent peptide testing. Consumers can request tests for purity and whether samples contain common contaminants, as well as whether they contain the quantity of the substance listed. The company doesn’t have in-house labs but instead acts as a middleman between labs and individuals. In a few weeks’ time, Finnrick told us, we’d know if our bodega peptides were the real deal.

In August, the results came in. The (relatively) good news: The samples contained low levels of heavy metals and endotoxins, meaning they likely weren’t actively harmful. The bad news: They weren’t peptides.

The testing for each substance found that they did not contain the active ingredients on their labels—the BPC-157, for example, had no BPC-157 within it. The negative results suggested that the vials were either mislabeled or, if they had at one point contained the correct ingredients, had been corrupted beyond recognition. Peptides are often sensitive to temperature changes and require refrigeration, so improper storage could degrade ingredients, for example.

What did they contain? Hard to say, according to Marco Krause, the chief executive officer of the laboratory that performed the tests for Finnrick.

“What we offer is simply a label claim analysis. So you send us what you claim to think it is, and then we run it against a standard and verify whether or not it’s the right compound,” he tells WIRED.

Peptides have surged in popularity in recent years, powered by endorsements from figures like US health secretary Robert F. Kennedy Jr. and podcaster Joe Rogan. While some of these substances are pharmaceutical drugs like GLP-1s and insulin, many of the buzziest peptides have not been put through the typical regulatory approval process for drugs. Despite the hype surrounding them, many of these substances are not legal to sell for human consumption in the US—some precisely because they haven’t gone through the drug approval pipeline—and evidence of their purported benefits is thin.

The sign at Mr. Green advertising the peptides noted they were for “research use only,” a term that labs can use in an attempt to shield themselves from legal liability. But as the test results show, there’s no guarantee what’s in the vials—and in some cases there are real dangers to those taking them.

According to Raphaël Mazoyer, Finnrick’s CEO, the samples WIRED tested appear to be “just duds.” Over the past three months, Mazoyer says, the company has seen an uptick in these kinds of results. Though he can’t say for certain what’s going on—in part, his company has been testing more samples as it has grown—he points to the popularity of so-called turnkey services, which help pretty much anyone open a peptide business.

“There are a whole bunch of labels popping up that have the same upstream vendor,” he says. Not all the peptides Finnrick tests are duds, but the nature of the industry means that businesses may use the same shoddy supplier across a number of different brands.