Is Vitamin C a Viable Treatment for Cancer in Dogs?

Benefits of Vitamin C

Vitamin C is one of the best known supplements on the market, but not many pet parents are aware of its benefits for dogs. Unlike humans, canines are able to produce their own vitamin C, which means supplementation in healthy dogs is typically unnecessary.

However, benefits have been seen when vitamin C is given to stressed dogs and those suffering from joint inflammation, cataracts, glaucoma, certain infections, and kennel cough. In addition, it boosts the immune system, which is one reason researchers turned their attention to the vitamin’s potential cancer-fighting properties.

Some clinical studies have shown that vitamin C therapy may improve cancer-related symptoms and prolong life in patients with terminal cancer, while other studies indicate the important nutrient may actively kill cancer cells. While these results are promising, more research is needed to know the full effects of vitamin C therapy on cancer in dogs. For now, though, many veterinarians are choosing to add it to cancer regimes, believing the potential benefits far outweigh any risks.

IV (Intravenous) Vitamin C Therapy

IV administration of vitamin C involves injecting the nutrient directly into the bloodstream. This is the most effective delivery method, because it allows plasma concentrations of the vitamin to reach levels high enough to potentially kill cancer cells and offer other benefits.

Subcutaneous or Intramuscular Vitamin C Therapy

Subcutaneous administration of vitamin C for treatment of canine cancer involves injecting a liquid form of the vitamin directly under the skin, where it is absorbed by the body. Intramuscular administration is similar, but involves injection direction into a muscle. Both of these approaches appear to be less effective than IV administration, but more effective than oral supplementation.

Oral Vitamin C Therapy for Dogs

Oral supplementation with vitamin C at high doses may result in some benefit, as it has been shown to boost the immune system and reduce inflammation. However, blood concentrations are probably too low following oral administration to actively kill cancer cells.

dog sleepingSide Effects of Using Vitamin C to Treat Cancer in Dogs

Side effects of too much vitamin C are generally mild and include upset stomach, gas, or diarrhea. In some dogs, diarrhea may become severe enough to affect health, requiring a dose reduction or discontinuation of therapy. Please consult your veterinarian with any concerns.


The short answer to the question of whether vitamin C is a viable treatment for cancer in dogs is a qualified “maybe”.  If your best friend is facing a life-threatening cancer diagnosis, and he doesn’t have calcium oxalate urinary stones or any other contraindications to using vitamin C, you should speak with your veterinarian about adding the vitamin to your dog’s treatment plan.  As Demian Dressler, DVM, states “Get your vet involved. Be your dog’s number one health advocate! Even if your canine companion does not experience a dramatic remission, there is at least evidence that quality of life may improve.”


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