Supplements: Selecting Supplements for your Pet

By Lauren R. Forsythe, PharmD, MBA, DICVP; Rania Gollakner, BS, DVM, MPH; Steve Marsden, DVM ND MSOM LAc DiplCH AHG, Shawn Messonnier, DVM and Cheryl Yuill, DVM, MSc, CVH

What are supplements?

A supplement is a concentrated ingredient that is added to the diet for nutritional or therapeutic benefits. Examples include vitamins, minerals, amino acids, herbs, botanicals, and enzymes. There is significant confusion around the terminology of food additives, and sometimes terms are used interchangeably. For clarity, the following terminology will be used in this handout.

  • Dietary supplements or dietary nutrients are substances that are added to a food, usually to make it nutritionally complete and balanced.
  • Therapeutic supplements, also called nutraceuticals or animal health supplements, are foods or food nutrients that are taken orally to prevent or treat disease. To have this therapeutic effect, a nutraceutical is usually taken in a larger dose than the daily requirement of that same ingredient when used as a nutrient.

How do I find out what a supplement is used for?

You may learn about supplements from a friend, a retail store employee, the internet, an advertisement in the media, or from a health care provider. Sometimes, this information may be incomplete or biased.

"The least biased information comes from publications that have some regulatory control."

Information that comes from the internet or other written sources may or may not be accurate or complete, depending on who has prepared the information. Some published information about nutraceuticals may be biased, especially if the source of the information is the manufacturer or retailer of the product.

The least biased information comes from publications that have some regulatory control (such as being regulated by a federal government agency). For example, with respect to herbal products, there is a database available through the U.S. Department of Agriculture that lists general uses and the reference sources for these uses. Another good source for information about supplements and manufacturer quality is found at

With respect to vitamins, minerals, amino acids, fatty acids, and other nutrients, some information can be found in standard nutrition textbooks. However, these sources may provide outdated information and may only include well-recognized and well-documented indications for specific nutrients. These sources may also discuss supplements as a nutritional requirement, rather than as a nutraceutical.

How do I know if a supplement is effective?

Few supplements and herbs have been subjected to rigorous scientific trials to determine their efficacy. Some supplements have been thoroughly researched in humans, but not animal species. Indeed, much information about supplements comes from anecdotal or testimonial evidence (someone tells you about their personal experience or about another patient who showed some benefit when taking the product). Although this information may be helpful, it may also be incomplete and may not represent the effects the supplement could have on your pet.

"It is common for supplements to be given to a patient along with other supplements, or in conjunction with other lifestyle changes."

It is common for supplements to be given to a patient along with other supplements, or in conjunction with other lifestyle changes. In these cases, it can be difficult to sort out exactly what effects can be attributed to the supplement and what may be attributable to other factors, especially if multiple changes were made simultaneously. For example, if a patient starts to take supplement Y, and at the same time changes their diet and starts an exercise program, then the observed changes may be due to any one of the factors, to a combination of all three, or even to a placebo effect.

To further complicate the issue of effectiveness, some supplements are only effective after they have been given for a period of time, and the patient may continue to show some of the positive effects for a few weeks after the supplement has been discontinued. For example, when using glucosamine to ease the symptoms of arthritis, it may take approximately four to eight weeks to show its effects and can take the same time to “wear off” after it has been discontinued.

How do I know if a supplement is safe to use for my pet?

Just because a product is natural does not mean that it is safe. All medicines and medicinal plants are potentially toxic if used inappropriately or given at high doses. Supplements can also have side effects, just like pharmaceuticals. Your veterinarian is the best source of information for the safety of supplements in domestic animals.

"All medicines and medicinal plants are potentially toxic if used inappropriately or given at high doses."

The use of supplements and nutraceuticals in veterinary medicine is a relatively recent practice, so some veterinarians may be unfamiliar with the indications and precautions for various products. Fortunately, reliable information about the clinical application of supplements is becoming increasingly available for veterinarians. Some privately maintained websites, such as, provide brief information and links to other relevant sites.

Another way to gather information about the use of a supplement in a certain species or for a certain disease is to consult the manufacturer of the product. If there is reliable information about the product's safety and efficacy in animals, the manufacturer should be able to provide it. If the manufacturer is unwilling to provide this information, it is safer for your pet if you err on the side of caution and do not use the product.

What is quality assurance or quality control?

Quality control provides a measure of assurance over what a product contains, with respect to its medicinal ingredients and its purity. Not all distributors share the same concerns about ensuring their products are high quality and free of contaminants, contain consistent levels of active ingredients, and retain their potency after processing. Supplements may not even contain the ingredients listed on the label.

Are there any regulations for packaging of supplements?

The U.S. Food and Drug Administration (FDA) requires that all ingredients in a pharmaceutical or food be listed on the label, and that none of these products be recognized as a potential health threat. The FDA also requires claims about a product’s ability to treat a disease be substantiated.

In North America, supplements, nutraceuticals, and herbs are not considered pharmaceuticals (and in most cases are not considered to be foods either). As a result, they are not regulated and not subject to the same strict requirements as pharmaceutical products. However, the FDA does require that these non-pharmaceuticals contain a disclaimer that says: “This product is not intended to diagnose, treat, cure or prevent any disease.”

Because of this lack of control, there is no guarantee of the package contents or product strength. It is left to the consumer to become informed about the integrity and ethics of the manufacturer to obtain any measure of assurance that the product is effective and unadulterated.

What should I look for on a label or package?

  • Every package should have the name and contact information of the product’s manufacturer. 
  • The label should contain information about the product's contents, ideally with a minimum analysis of the active ingredients. 
  • The label should contain information about any inert or carrier substances that are present, such as milk, sugar, whey, and vegetable or animal proteins.
  • Labels for herbal products should include the Latin name of the plant, a harvest date or an expiration date, the part of the herb used, and the quantity of active constituents.
  • When the label includes the USP seal in a prominent location, it indicates the product contents have been evaluated and the listed ingredients are accurate.

Who can give me advice about treating my pet with a supplement?

Your best source of professional nutritional advice is a licensed veterinarian who is knowledgeable about the and about alternative medicine in general. Veterinarians have been trained about the anatomy and physiology of animals and are expected to be knowledgeable about the treatments they prescribe, including toxicity and predictable side effects.

What should I do if my pet shows an unexpected reaction to a supplement?

Always report unexpected reactions to your veterinarian or the person who recommended the supplement, and to the manufacturer. There are often government agencies that collect and collate this information, and it is strongly recommended that these agencies also be informed of the concerns.

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