Should dogs be given supplemental Vitamin C?

Should dogs be given supplemental Vitamin C?

Posted by Jennifer Carter on May 17th 2019

As pet food consumers, we are inundated with different supplements options everywhere we look. They are available on the shelves in pet stores and the salespeople found in those stores are always guiding us to supplement our dog’s diets on a regular basis. Should vitamin C be included in that supplementation?

Unlike people, dogs are not dependent on vitamin C being supplied in their diet. If you are feeding a fresh, balanced diet there should be no reason for additional supplementation. Healthy dogs have a metabolism that allows them to make their own vitamin C in the liver when given the raw ingredients in their food (1). Dogs do not get human deficiency diseases such as scurvy. In the Volhard Natural Diets, the dogs get Vitamin C naturally from whole foods such as kelp, parsley, alfalfa, and garlic.  

There are different kinds of vitamin C such as Calcium Ascorbate, Ascorbic Acid, Ester C and Sodium Ascorbate. Calcium Ascorbate is necessary for the breakdown of protein. This type of Vitamin C should be fed to the dog with every meal because it cannot be stored and is water soluble. This type of Vitamin C is thought of as gentle and has the fewest side effects such as diarrhea or indigestion (2). Calcium Ascorbate is Ph 7 which is neutral and has shown to benefit dogs with arthritis and the reduction of stress. Ascorbic Acid is a naturally occurring Vitamin C and found in most human Vitamin C pills. It is not efficiently bioavailable to dogs and can cause some intestinal distress. Ester C is a time release product of calcium and Vitamin C, neutral in Ph and does not cause GI distress. This type has not been researched to see if it is used by the dog’s body or just passed. Finally, Sodium Ascorbate is another readily available easily absorbed type of Vitamin C, Ph neutral powder. It stays in the system 2x as long as ascorbic acid and has show benefit to dog’s with Addison’s disease if given in low doses.

So when does vitamin C supplementation make sense? Despite the absence of scientific studies confirming that extra vitamin C actually helps dogs, veterinarians, owners, and breeders continue to discuss the subject (3). Holistic vets will tell you that when the dog’s body is stressed, sick, or worn out it uses its vitamin C as part of the repair process (4). This constant need for vitamin C sometimes runs down the body's reserves and boosting levels through supplementation may be beneficial. If a dog has liver disease or unusually high metabolic requirements, vitamin C supplementation may offer a benefit to the dog in order to keep up with its body’s needs. 

Some commercial dog foods contain added synthetic vitamin C, under the assumption that its natural antioxidant properties benefit the dog’s immune system. Supplements, in general, are very popular and with some deficient diets or diets that have been overly processed with heat require the addition of synthetic vitamins to replace those lost in processing. Vitamin C is, in fact, popular and appears widespread among health-conscious people. Extra vitamin C is not dangerous to dogs due to its water solubility so whatever the dog doesn’t use is excreted in their urine in the form of oxalate. The only caveat to this is that elevated urinary concentrations of oxalate can increase the risk of calcium oxalate bladder stones developing in the urinary tract, especially in male dogs. The oxalate bladder stones appear when high doses of vitamin C change the pH of urine and make it more acidic than normal. This is a potentially serious complication which could cause bloody urine or a urinary blockage which requires emergency surgery. This is an outcome one does not want to experience.

There are warranted situations where the supplementation of vitamin C can be beneficial. Even a healthy dog may need their immune system boosted in times of vaccination and could benefit from a vitamin C supplement. In situations where a dog is fighting cancer, degenerative diseases, experiencing chronic illnesses, managing stress then vitamin C makes sense. 


(1) “Ascorbic Acid”, Nutrient Requirements of Dogs and Cats, National Research Council, National Academy of Science, Washington, DC (2006), p. 234

(2) The Holistic Guide for the Healthy Dog, Wendy Volhard 2000, pg 40