Anything found naturally in a horse’s body is allowed to be there on a drug test, right? Not necessarily.

Cobalt, for example, is a trace mineral found in B vitamins that horses require in tiny amounts for their bodies to function correctly. As a result, all horses have trace amounts of the substance in their systems. But when tests reveal higher doses of cobalt—after a larger dose of the substance is administered, for instance—it often means a trainer or handler attempted to gain a competitive advantage. This is considered doping.

To confound things, researchers don’t yet understand how high a cobalt dose must be to affect a horse’s body—just that it could be putting both horses and their handlers at risk. At the 2016 American College of Veterinary Internal Medicine Forum, held June 8-11 in Denver, Colorado, Teresa Burns, DVM, PhD, Dipl. ACVIM, an assistant clinical professor of equine internal medicine at the Ohio State University College of Veterinary Medicine, in Columbus, shared study findings on the topic.

Human doctors used cobalt to treat anemia (essentially by increasing erythropoiesis and, therefore, the blood’s oxygen-carrying capacity) in humans for decades. However, it was associated with a variety of adverse effects, including gastrointestinal, neurologic, cardiovascular, and thyroid problems. As a result, doctors have largely ceased using it. Some athletes, however, continue using it as a doping agent, as an increased oxygen carrying capacity is thought to improve an athlete’s aerobic capacity and endurance.

In the past few years, that same trend appears to have spread into the