One topic we’ve had a lot of questions about in recent months is supplements (most commonly calming supplements), and how to figure out what aligns with US Equestrian’s rules for competition.  

Let’s walk through the process of determining whether a supplement is ok to use.  

Whatever you believe may ail you or your horse, there is probably a supplement out there that claims to fix it. A recent U.S. Government Accountability Office report showed the human supplement market grew from approximately 4,000 products in 1994 to as many as 90,000 in 2017, and the horse supplement world has seen a similar explosion in product availability. For some owners, the prospect of putting a horse on a supplement seems like low stakes – maybe it will help, and many people believe it can’t hurt anything. But if your horse competes in sanctioned events – whether that’s through USEF or another regulatory body – they may be subject to drugs and medications rules that conflict with a product’s ingredients. 

Finding out whether you need to be concerned about the supplement you’re using is not as straightforward as looking up the product name on a list, and unfortunately, whether or not a supplement is free from risk of a positive test isn’t a question with a simple yes or no answer. 

“We don’t have a list of ‘safe’ supplements, and we don’t issue seals of approval – that’s a common myth,” said Dr. Stephen Schumacher, chief veterinary officer at USEF. “If you see a product claiming to be ‘show legal’ or ‘approved’ by us, please know that is a marketing choice by the product manufacturer, not a determination by us.”  

The reason is that supplements (human and animal) are not regulated by the Food and Drug Administration, which means manufacturers can and do change formulas and labeling without issuing notice to customers. They’re also not held to the same standards as drugs to ensure that labels match product contents or to ensure ingredient consistency between batches. Because of all these moving pieces, USEF and members have to approach each product individually. 

If you're considering the use of a particular supplement in competition, you should first look at the label of the supplement together with the USEF Drugs and Medications Guidelines, which contain a list of examples of prohibited substances.  If you’re not sure if an ingredient is ok, or if there’s an ingredient on the label you don’t recognize, you can always email our Drugs and Medications office ([email protected]) and ask them to review the label. 

"If this is for something you’ve already purchased or are feeding your horse, we’ll ask you to take a photo of the container you have and send it to us,” said Schumacher. “We have found there are sometimes differences in labeling between two containers of the same product bought at different times or from different sources. 

“Our staff will review the ingredients list and let you know what, if anything, may be prohibited.”  

Keep in mind that ingredients may have common names as well as chemical names, and it’s possible the same thing could be noted differently on different products. A good example of this is caesin, which is also called alpha-casozepine and is a prohibited substance due to its impact on the central nervous system.  

Some companies are reluctant to divulge what they consider to be the “secret sauce” of their product and may list “proprietary herbal blend” or other phrases on their labeling in lieu of naming specific ingredients. That negates our ability to check that ingredient for prohibited substances. If there’s something on a label that our experts are unsure about, they will let you know.  

So, if a label doesn’t contain any prohibited substances, that means you’re all good, right? Not necessarily. 

“Even if a label doesn’t contain any prohibited substances, the staff will caution members that you accept a degree of risk with the use of calming (or any other) supplements,” said Schumacher. “The FDA is not testing products to guarantee safety, efficacy, quality, or even consistency in ingredients between batches. We can’t be as certain of what’s in a supplement as what’s in an FDA-approved drug – and neither can you.”  

Although rare, there have been instances of positive drug tests that trace back to supplements whose labels did not warn consumers of the presence of a prohibited substance in the product.  

And why are there so many common supplement ingredients on the prohibited list, anyway?  

USEF rules require us to regulate the use of substances and drugs that might affect performance by stimulating or depressing the cardiovascular, respiratory, or central nervous systems of horses. (See GR410 for more information.) 

“It’s all about creating a safe, level playing field for horses and competitors,” said Schumacher. “We know it can be challenging to navigate the world of supplements, which is why we stand ready to help you understand the level of risk that may or may not be present in a product. We don’t want people to get positive tests any more than they do.” 

Learn about additional cautions to consider with supplement use in this August 2025 article.