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Dog Nutrition

Sodium Selenite in Dog Food: Vet-Verified Nutrition Info, Risks & FAQ

Annaliese Morgan
By Annaliese MorganUpdated on June 17, 2026
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Feeding your dog a safe and healthy diet every day is an essential part of pet parenting and one that many owners feel like they are always searching for. New information is constantly being unveiled or discovered, with better or new ingredients being added or removed and medical science evolving. It’s creating a world where pet nutrition is a forever-changing and -expanding industry.

Over the years, as quality, standards, and choices of dog food have increased, so have pet parents' expectations and awareness. A recent controversial nutrient called sodium selenite, a mineral found within dog food, has been and still is causing much discussion among owners, experts, and dog food manufacturers.

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What Is Sodium Selenite in Dog Food?

Sodium selenite is added as a supplement to commercial dog food. It is typically listed on the ingredient list with this name but may sometimes be bunched under the umbrella term “trace elements.”

Sodium selenite is an inorganic synthetic form of the natural mineral selenium, an essential trace mineral required by dogs. It's found in dairy, meat, fish, and whole grains. Due to the short shelf life of these products and how most of the natural selenium from animal sources is lost during the manufacturing process, the synthetic version (sodium selenite) is favored by dog manufacturers and, therefore, added as a supplement to the food.

Image Credit: 279photo Studio, Shutterstock

Is Sodium Selenite in Dog Food Necessary?

Sodium selenite is an inexpensive, synthetic form of the natural essential trace mineral selenium. Minerals, much like vitamins, are a vital requirement for dogs, and they require selenium specifically to help maintain the normal functioning of their thyroid gland, to maintain immunity, for its function as an antioxidant and role in reproduction.

A deficiency in selenium can produce health problems, but due to reasons cited earlier—for example, the expense of selenium, the mineral often being lost in processing, and high doses of selenium found to be toxic—the alternative, sodium selenite, is predominantly used in very small amounts.

This is done because the essential mineral still needs to be supplied in the dog food; otherwise, deficiencies can occur, which can cause health issues and certain conditions in dogs.

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Signs Your Dog Is Deficient in Selenium

Signs of a clinical deficiency in selenium are uncommon and rarely seen by veterinarians in modern times. Studies where both selenium and vitamin E were deficient in the diet of 5–8-week-old Beagle puppies led to signs of muscle weakness, anorexia, depression, breathing difficulties, and coma.1

A long-term lower-level deficiency has been linked with various health concerns, including the formation of urinary stones (calcium oxalate calculi), the development of cancer, a reduction in a male dog’s fertility, and slow recovery from parasitic diseases.2

Signs of Selenium Toxicity

There are no known records of naturally occurring selenium poisonings in dogs. In studies, chronic selenium poisoning from food caused signs of anorexia, lack of growth, change in hair coat and hair loss, anemia, a buildup of fluid in the abdomen, and eventually, death.3

Potential Side Effects of Sodium Selenite

As with any excess of minerals or vitamins, toxic effects can be experienced by your dog if too much sodium selenite is consumed. It is this worry, along with the unnaturalness of the substance, causing some owners to be against the use of sodium selenite in dog food.

If sodium selenite is only consumed in minute quantities, as recommended by organizations like The Association of American Feed Control Officers and the FDA, there seems to be little evidence to suggest that it's dangerous for dogs or will produce any side effects.4

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Frequently Asked Questions

Are There Dog Foods That Do Not Contain Sodium Selenite?

Yes, some dog foods and diets that do not contain sodium selenite are available. This is a conversation worth having with a veterinarian or veterinary nutritionist to determine if this is the best route for your dog before making your choice.

How Can I Check the Selenium Levels of My Dog?

Although not commonly performed, there are blood tests that veterinarians can use to check the levels of selenium in your dog’s serum (a component of blood).

Can Selenium Help Prevent Cancer?

Yes, animal studies have found that selenium is beneficial in the prevention of cancer and is particularly helpful in older canines. Please discuss this with a vet to determine whether adding supplements to or swapping your dog's diet is the right decision for your pet.

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Conclusion

Selenium or sodium selenite is a necessary mineral for your dog to consume in the correct quantities. Currently, there is no evidence to suggest that sodium selenite, if kept within recommended guidelines, is harmful to canines. It appears that the controversy surrounding its safety is unfounded, though the long-term effects of this supplement have not been studied.

Reports have found that sodium selenite is safe and effective to use in dogs. It is important to feed a balanced and complete diet to your dog to maintain their health and prevent nutritional deficiencies and health problems. Your discernment, backed with advice from your veterinarian, is the best way forward to deciding the correct diet and if supplements are needed for your pet.

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Sources

Featured Image Credit: New Africa, Shutterstock

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Annaliese Morgan
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