Six sports supplements sold in New Zealand and Australia have been found to contain anabolic steroids.
Researchers from Otago University now believe unsuspecting athletes could run the risk of positive doping tests and suffer potential health risks.
One hundred and sixteen sports supplements were tested by Australian and Otago University scientists.
"Out of those 116 supplements, six of them tested positive for an androgen, even though on the label there was no androgen declared," researcher Alison Heather says.
Androgens are a type of anabolic steroid that promotes bone and muscle strength.
They also pose a health risk, including liver damage, acne, aggressive mood swings and endocrine cancer, even heart disease.
For athletes, there are even more risks.
"Even trace amounts of some of these androgens would lead to a doping violation," Ms Heather says.
She says the researchers can't name the products involved just yet for legal reasons
Drug Free Sports New Zealand chief executive Nick Paterson is concerned with the latest findings, although he says they are not entirely surprising.
"It's something that we've been warning against for a very long time. Supplements use in NZ has been on the rise for some time and you never quite know what's going in to your supplement."
Drug Free Sport's advice to athletes and gym goers is, if you don't know what's in your supplement, don't take the risk.