Not all supplements are created equal

In recommending supplements, we as veterinarians need to use the best available evidence-based research and clinical experiences

Before selecting a supplement to give to a patient, do your due diligence by asking the manufacturer or supplier a range of questions.
Before selecting a supplement to give to a patient, do your due diligence by asking the manufacturer or supplier a range of questions.

Unfortunately, with the majority of these products, marketing overrides science. Owners spend money on products that may or may not be effective and in the case of some, may contain extraneous harmful ingredients.1 Many people presume supplements are safer than drugs as they are perceived to be “natural.” The reality is there is very limited safety data on dietary supplements for pets to determine safe use.2 What safety data is available is often only known for use in people. In 2015, there were 23,000 trips to the emergency room for humans that were directly related to consumption of dietary supplements.3

Although there are legitimate pet supplement companies that monitor the contents of their products, veterinarians need to have direction in their product selections, as supplements are not regulated by the U.S. Food and Drug Administration (FDA).

The market for pet supplements sold over-the-counter (OTC) exceeds half a billion dollars, with a healthy rate of growth.4 Direct sales of veterinary supplements account for half. It is unknown how much of the $30-billion human supplement market is used on pets. That brings up the important issue of what to consider when recommending a supplement for a client’s pet.

Oversight and control

There are a few things to keep in mind about veterinary supplements that may explain why their quality and “claims” may be so lax:

  • they are marketed with less direct oversight than approved drugs; and
  • they are neither drugs nor are they approved by the FDA, which means they have not been subjected to its controls for safety and efficacy.

In recommending supplements, we as veterinarians need to use the best available evidence-based research and clinical experiences. We also must assess independent scientific literature and product information from the manufacturer. Further, we should avoid extrapolating claims of safety from human supplements when giving such products to pets.

Since supplements are not subjected to FDA testing for approval, marketing, and quality, we are fortunate to have organizations that aid in evaluating products. There are two main organizations that routinely monitor supplements for both humans and pets*:

  • National Animal Supplement Council (NASC) verifies the use of quality ingredients, proper production processes, continuous product and data monitoring, and allowable product claims. Some readers may have seen NASC’s seal on several veterinary products.
  • is an independent site with a small subscription fee that evaluates supplements for quality, heavy-metal toxicity, correct product labeling, and price comparison. On a biweekly basis, it answers questions about supplements, interactions with prescription drugs, optimum conditions for taking the supplement, etc.

No such thing as a silly question

Here are some important questions to consider when selecting a supplement for your patients:

  • Who formulates the product? What expertise do they have?
  • Who can you call if you have questions regarding the product, need advice, or want to discuss a patient who is experiencing an adverse reaction?
  • How long has the company been selling pet supplements?
  • What sort of testing and quality standards/quality control does the company have?
  • Is the supplement tested by an independent lab?
  • Does the product label have a lot number and expiration date? If it doesn’t, how can it be traced if an adverse reaction occurs?
  • Is the manufacturer willing to disclose the point of origin of the product’s ingredients?
  • Does the product say “manufactured by” (meaning it is made by that company) or “manufactured for” or “distributed by” (meaning it is sold by that company—someone else makes it).

One of the reasons we need to be diligent about the supplements we are recommending for our patients is that while most dietary supplements sold in the U. S. are manufactured here, their ingredients generally come from other countries. There is no requirement for supplement companies to include on the label the country of origin of its ingredients, although some do. Also, manufacturers may change the source of the ingredient over time. If a supplement is made in China (many of them are), suppliers sell more than one version of an ingredient, which can differ in quality and cost. The company that makes the final product decides what grade to purchase and use, and this can often change. As of May 15, 2019, CVS Pharmacy introduced third-party testing for all vitamins and supplements sold at its stores. Its “Tested to be trusted” program requires all dietary supplement products it sells to be certified by NSF International (a Michigan-based product testing, inspection, and certification organization) or by United States Pharmacopeia (USP) to include verification of ingredients, as well as a review of contaminants present. CVS states more than 1,400 products have completed testing, with seven percent of them failing. They were consequently removed from store shelves.

Several reports of prescription drugs found in human supplements made headlines in October 2018 when 20 percent of supplements tested by the FDA were found to contain prescription medications that had no business being included (e.g. muscle-building supplements that contained actual steroids, weight loss products with sibutramine [removed from the U.S. market in 2010 due to cardiovascular risks], and laxatives). Other drugs found in supplements include antidepressants and antihistamines. Fewer than one half of these adulterated products were voluntarily recalled. One can only imagine if one of these OTC human supplement products was given to pets. There have been anecdotal reports of low doses of 5-hydroxytryptophan (5-HTP) used in dogs for the treatment of anxiety. However, in one reported case, a Dachshund ingested 29 tablets of its owner’s 5-HTP supplement, resulting in a potentially fatal serotonin-like syndrome. Each tablet contained 100 mg 5-HTP and 820 mg xylitol (also toxic).
The dog recovered after three days of hospitalization.5

Some specific veterinary supplements that have been evaluated include a study partially funded by Nutramax Laboratories for chondroitin sulfate. It found deviations from label claims in 84 percent (nine out of 11) products tested, the amount ranging from zero to
115 percent.
found at least 50 percent of products containing chondroitin sulfate mislabeled. Two out of three veterinary products contained no chondroitin despite claims on the label. The website also reviewed Milk thistle (a human supplement) and found eight out of 11 products failed because they contained less than 50 percent of the labeled ingredient. In a review of omega fatty acids, three out of 44 human products failed, while three out of six veterinary products failed, containing only 25 to 33 percent of the labeled ingredients. Probiotics reviewed by reported up to 93 percent of “acidophilus” or other beneficial bacteria are missing in some supplements. Regarding probiotics, recommends the following to assure quality:

  • the label should list all types of bacteria or yeast, including genus and species, and the number of colony forming units (CFUs);
  • the number of viable organisms (typically one billion to 10 billion CFUs are recommended in humans) per day;
  • the viability of organisms; and
  • the presence of any contaminating organisms, including E. coli, Salmonella spp., or spores.6

It all sounds scary and yes, we need to do our due diligence when recommending, selecting, and administering any supplement for our pets and ourselves. Unfortunately, consumers follow blogs and advertisements that
tend to override our evidence-
based science when it comes to supplements. Our clients are much more likely to listen to glorified advertisements with little to no validity than our educated recommendations. When challenged with questions about various supplements, I provide the evaluation and/or check for NASC certification. Both NASC and are all we have at the present time to evaluate these products and thankfully we have both! With CBD now hitting the market, product evaluations for quality and content will be essential, yet legally in most states, we as veterinarians are not even allowed to answer questions
or provide any guidance about
these products.

So what can we do as concerned veterinarians to aid our clients when selecting or recommending a supplement? In “Vitamin and Mineral Supplements–What Clinicians Need to Know,”7 the author, JoAnn E. Manson, MD, DrPH, advises her clients consult, USP, or NSF International (the latter two being nonprofit organizations) when considering human supplements. As veterinarians, we can utilize those organizations and look for the NASC seal on products. More importantly, ask! The questions discussed in this article will help in determining a product’s quality and ensure our patients are receiving safe and effective supplements.

Alice Jeromin, RPH, DVM, DACVD, is practice owner of Veterinary Allergy & Dermatology Inc., in Richfield, Ohio. She graduated from the University of Toledo with a BSc in pharmacy and worked as a hospital pharmacist before earning a DVM degree at Ohio State University College of Veterinary Medicine. Dr. Jeromin is a board-certified veterinary dermatologist, adjunct professor at Case Western Reserve University College of Medicine, past president of the Cleveland Academy of Veterinary Medicine, and was chair of the supplement committee of the American Veterinary Medical Association’s (AVMA’s) Council on Biologics and Therapeutic Agents. She continues to teach and lecture, and lives with her husband (a pharmacist), six rescued cats, and two elderly golden retrievers. Jeromin can be reached via email at

* The following organizations monitor supplements for human consumption only:

  • Started in 2012 in San Francisco, Labdoor ranks human supplements for label accuracy, purity, nutritional value, efficacy, and safety;8
  • United States Pharmacopeia (USP); and
  • NSF International.


1 Tucker J, Unapproved pharmaceutical ingredients included in dietary supplements associated with U.S. Food and Drug Administration warnings. JAMA Network Open, October 12, 2018;1(6):e18337.

2 Safety of dietary supplements for horses, dogs, and cats. Report in Brief, The National Academies 2008. The National Academy of Sciences Committee on Examining Safety of Dietary Supplements: Jim E.Riviere, Chairman, North Carolina State University.

3 Geller A, Emergency department visits for adverse effects related to dietary supplements. JAMA 2015;373:pp153-160.

4 Lummis D, Vet community support is essential to pet supplement market growth. Veterinary Practice News, 24; July 2017, pp48-49.

5 Ortolani, Clinical case reports., 2019.

6 Boothe D, Neutraceuticals: Myth or must? CVC San Diego Proceedings in DVM360, November 1, 2010.

7 Manson J, Vitamin and mineral supplements-what clinicians need to know. JAMA 2018;319(9) pp. 859-860.

8 Smith P, Don’t trust the label on your supplements. Outside Magazine, July 5, 2018.

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