Black-Market Peptides Show High-Dose Risk in New Tests

The demand for unapproved peptides, fueled by social media trends, has prompted a surge in testing requests, according to analytical chemist Grace Hamann. Her laboratory, Leeder Analytical, now dedicates about half of its work to testing these substances, a field she had never encountered a year prior.

“

Now about 50 per cent of my job is testing peptides … the growth has been exponential.

"The growth has been exponential," Ms. Hamann stated, noting that requests began arriving almost daily in October 2025. The lab invested about a month in developing accurate testing methods to meet this demand from consumers and the wellness industry.

Recently, Leeder Analytical tested three vials of counterfeit retatrutide, a weight-loss peptide still in clinical trials and unapproved for human use, obtained from black-market sources. The results were unexpected: while one vial had less peptide than indicated, two contained significantly higher concentrations than labeled.

“

In October 2025, we started to get almost daily requests for testing.

Of the 18 counterfeit retatrutide samples tested by the lab this year, only one matched its label claim. Approximately 30 percent showed higher concentrations, another 30 percent showed lower concentrations, and one vial contained none of the peptide at all. "You would expect if you're buying an unregulated product that they'd want to cut costs [and include less of the drug] … but the fact that we've had almost equal amount to be over 100 per cent than under 100 per cent, surprises me," Ms. Hamann said.

“

We spent about a month to set up a method to make sure that we could accurately test and report results.

Researchers from the University of Queensland's School of Public Health and harm reduction organization PED Test Australia funded and arranged the testing. UQ peptide researcher Tim Piatkowski noted that the high-dose results contradicted their observations in steroid testing, where underdosing is far more common. "I definitely didn't expect that level of overdosing," he said. The findings, reported to the Drug and Alcohol Review journal, suggest that inaccurate dosing, not just counterfeit ingredients, poses a significant risk.

“

You would expect if you're buying an unregulated product that they'd want to cut costs [and include less of the drug] … but the fact that we've had almost equal amount to be over 100 per cent than under 100 per cent, surprises me.