Given the popularity of Vitamin C supplementation among people, pet parents are now questioning whether they should get more Vitamin C for dogs either to treat diseases, or to prevent them. Let’s take a quick look what research has to say on the benefits and side effects of Vitamin C for dogs.
The thought of Vitamin C conjures up images of citrus fruits like lemons and limes, and perhaps even some chalky tablets from the health food store. Vitamin C is essential in our diets and without it, we humans can suffer some pretty ill effects. Taking large doses of Vitamin C can be useful in fighting a number of our ailments, including the common cold.
Unlike humans, dogs do not require Vitamin C in their diet. Their bodies are truly unique in a way that dogs can make their own Vitamin C . And in dogs, Vitamin C is synthesized in their liver .
If your dog is completely healthy, a Vitamin C supplement is often not that necessary. However, supplementing your dog’s diet with Vitamin C can be a good idea and potentially provide a lifetime of benefits.
What is Vitamin C for dogs?
Vitamin C, also known as ascorbic acid, is a water-soluble vitamin found in a variety of foods, such as citrus, berries and leafy greens like kale. Vitamin C is also a powerful antioxidant.
How does it work for dogs?
In your dog’s body, byproducts of metabolism are called reactive free radicals. These free radicals can cause damage to other tissues in the dog’s body and this process is called oxidative damage. Antioxidants are substances that counteract or neutralize free radicals, thus preventing damage to other cells and tissues in canines.
Many ailments in dogs are linked to high levels of oxidative damage, such as cancer, autoimmune disease and mental decline. When it comes to dogs, Vitamin C will often be used primarily as an antioxidant, especially in high levels. The more Vitamin C available in the dog’s body, the better it works.
Why should my dog take Vitamin C?
Supplementing your dog’s diet with Vitamin C can be a useful and natural treatment for certain ailments.
High doses of Vitamin C for dogs may help treat conditions such as:
- Cognitive Dysfunction “Doggie Dementia” 
- Toxin ingestion, such as acetaminophen 
- Fracture repair 
- Canine ringworm 
- Dog arthritis [6, 7, 9]
- Cancer in dogs 
- Dog liver disease [11, 12, 15]
Can Vitamin C be used to prevent disease in dogs?
Yes! Veterinary experts recommend:
“Begin with a daily dose of vitamin C in the preferred form of Ester-C™ as follows: 250–500 mg daily for small dogs, divided twice daily and given with food; 500–1000 mg daily for medium to large dogs , and given as above; and 1000–2000 mg for large and giant breed dogs.” 
Talk to your veterinarian about specific dosing of Vitamin C for dogs. Your canine’s health status and diagnosis will determine what dose should be used. Also, Vitamin C for dogs supplements could interact with medications your dog is taking, and it’s vitally important to keep a close track of all treatments your canine is going through .
If your veterinarian is not familiar with using Vitamin C for dogs, seek out a holistic veterinarian’s opinion. However, as with any “holistic” methods, we always ask you to approach such practices with a healthy amount of skepticism.
Can it be given to dogs with their food?
Yes, Vitamin C for dogs can be given with their kibble or any other type of dog food.
Note that Vitamin C for dogs can cause problems with the acid levels in your canine’s stomach. It is best to give the dog supplements that contain calcium ascorbate or sodium ascorbate instead of ascorbic acid when given with food .
Giving a full Vitamin C supplement dose all at once can cause vomiting or diarrhea in some dogs. It is best to divide the total dose into a morning and evening portions.
Better yet – feed your dog whole foods on a daily basis that naturally contain high levels of Vitamin C, such as blueberries, cranberries, apples, ginger, grape seed extract and pomegranate.
When should Vitamin C not be used, or can it be ‘too much of a good thing’?
As a water-soluble vitamin, your dog’s body will simply flush excess Vitamin C into the urine. It does not concentrate in canine’s body tissues.
However, too much Vitamin C for dogs can increase the acidity of the stomach in some pets, possibly causing irritation or contributing to ulceration, as previously noted:
“As dogs can synthesize their own vitamin C, the need for supplementation is controversial. To avoid acidic effects on the stomach, calcium ascorbate or sodium ascorbate can be used instead of ascorbic acid (Straus 2007; Sanghi et al. 2009).” 
Vitamin C supplementation can be harmful for some dogs, especially those suffering with bladder stones or specific copper or iron storage disease of the liver [10, 11, 12].
Dalmatians are prone to developing uric acid stones. If your Dalmatian has had problems with these stones in the past, or with crystals in the urine, it is not recommended to give them any Vitamin C supplements. Vitamin C causes the urine to become more acidic, which can cause more stones to form .
Be sure to read the labels of all dog health supplements, because Vitamin C is a popular addition to bladder health and joint support supplement products.
The bottom line
If your dog is generally healthy, supplementation with vitamin C is most likely unnecessary.
If your dog suffers from a chronic condition, is stressed, shows clear signs of rapid aging or is unable to produce enough Vitamin C, supplementation is worthwhile. As mentioned below, several studies have shown that Vitamin C levels seem to be lower in dogs that are fighting diseases (i.e. parasitic skin disease, cancer and so on).
Ask your veterinarian if Vitamin C is right for your pet. It can certainly make a difference for some dogs.
Want to learn more about vitamin C for dogs?
3 most common sources of Vitamin C for dogs:
- Joint supplements, including collagen concentrate products
- Fruits and vegetables, such as blueberries, raspberries, apples, carrots.
Vitamin C for dogs could be a worthwhile treatment for much more than we realize now.
Improved immune function in dogs
Results of a small study (15 dogs) suggest that supplemental Vitamin C and E can increase numbers of lymphocytes, a type of white blood cell. In theory, this increase could mean an improvement in dog’s immune system response and/or function .
“Three treatments (0, 30, 60 mg vitamin C) were tested in a 3 x 3 cross-over study in three periods of 36 days. Pre-prandial blood samples were taken for analysis of vitamins C, E, A, retinyl palmitate and stearate, antioxidant status [Thiobarbituric acid reactive substances (TBARS) and uric acid], biochemical and haematological analysis. Subpopulations of lymphocytes, mitogen-induced peripheral blood mononuclear cell proliferation (PBMC) and serum IgA and IgG concentrations were determined.
There was a trend (p = 0.056) for an increased plasma vitamin C concentration by vitamin C supplementation. There was no evidence that dietary treatment altered neither the other plasma vitamin concentrations nor TBARS and uric acid concentrations nor the subpopulations of the lymphocytes except for the number of CD4+ lymphocytes that increased with vitamin C supplementation. There was no effect of vitamin C on serum IgA and IgG concentration. A significant time x treatment interaction was demonstrated on PBMC’s to pokeweed, with an increase observed by 30 mg vitamin C supplementation but a decrease by 60 mg vitamin C supplementation.
There was no clear evidence for an effect of dietary vitamin C on antioxidative capacity in healthy dogs fed a diet with vitamin E concentrations well above the recommendations. Yet, a limited number of immunological parameters were slightly affected.”
Treatment of dog arthritis
A prominent holistic veterinarian, Dr. Jean Dodds, of Garden Grove, California, says this about vitamin C for dogs and arthritis:
“Ascorbic acid (vitamin C) is necessary for the synthesis of type II collagen, the most abundant protein in cartilage. Studies indicate that vitamin C may protect the cartilage, especially when taken in high doses.” 
Treatment of parasitic diseases
Most people are aware that Vitamin C plays a vital role in the dog’s body. A study in 2013, published in the Journal of Veterinary Parasitology shows that decreased levels of Vitamin C is associated with generalized canine demodicosis. Generalized demodecosis is a skin infection with the demodex mite, also known as “red mange.”
Generalized demodecosis has long been associated with poor immune function and may have a genetic component. Treating this skin condition in dogs can take several months and canines are not considered “cured” until their skin tests are negative for about a year after their last treatment.
“…Vitamin C levels were significantly (P<0.05) lower in diseased dogs when compared to healthy control. From the present study, it was concluded that generalized demodecosis in dogs is associated with significant alteration in trace elements and oxidant/anti-oxidant imbalance and this imbalance might be secondary to changes caused by demodectic mange.” 
From this study, it is difficult to determine if the low Vitamin C levels in dogs contribute to the disease or if the disease process caused lowered Vitamin C levels. Regardless, it may be beneficial to consider vitamin C supplementation if your dog suffers from generalized demodecosis. It has not been proven as a helpful adjunctive therapy, but it may be something worthwhile to discuss with your veterinarian.
Treatment of canine cancer
Some holistic veterinarians treat cancer with intravenous high-doses of vitamin C. Naturally, there is not a lot of research or literature that shows that this treatment is effective, but many holistic vets claim that it works. The results of a recent study show that dogs being treated for lymphoma (with chemotherapy) have lowered levels of vitamin C in their bodies. It is possible that supplementation with Vitamin C for dogs could be beneficial in fighting lymphoma in canines:
“Prospective, observational study. Measures of oxidative stress [malondialdehyde and total isoprostanes (isoP)] and antioxidants [alpha-tocopherol, gamma-tocopherol, oxygen radical absorbance capacity (ORAC), and glutathione peroxidase (GSHPx)] were assessed in dogs with newly diagnosed lymphoma before treatment compared with healthy control dogs. The same parameters were measured in the dogs with lymphoma on week 7 of the chemotherapy protocol when all dogs were in remission.” 
At baseline, dogs with lymphoma had significantly lower alpha-tocopherol and gamma-tocopherol but higher GSHPx, ORAC, and isoP compared with healthy controls. In the dogs with lymphoma, alpha-tocopherol concentrations were higher and ascorbic acid were lower after treatment.
Results of this study suggest that dogs with lymphoma have alterations in oxidant and antioxidant concentrations and that the status of some of these biomarkers normalize after remission. Further studies are warranted to determine whether antioxidant interventions to correct these are beneficial in the treatment of canine lymphoma.
- Twedt, David. Applications of Nutraceutical Antioxidants in Veterinary Medicine. Western Veterinary Conference Proceedings. 2009.
- Katherman, A. and Shell, L., Cognitive Dysfunction. Veterinary Information Network (VIN) Associate Database. July 3, 2014.
- Plumb, Donald. Plumb’s Veterinary Drug Handbook. 8th Ascorbic Acid/Vitamin C. January 1, 2015.
- Silant’eva, TA, Krasnov, VV. Stimulation of pelvic fracture healing by local injection of autologous plasma in combination with metabolically active substances that have an antioxidant and antihypoxic effect. Vestn Ross Akad Med Nauk. January 2014;0(7-8):137-43. [study]
- Beigh SA, Soodan JS, Ringh R, Khan AM, Dar MA. Evaluation of trace elements, oxidant/antioxidant status, vitamin C and Beta-carotene in dogs with dermatophytosis. 2014 Jun;57(6):358-65. [study]
- Sanghi D, Avasthi S, Srivastava RN, Singh A. Nutritional factors and osteoarthritis: a review article. Int J Med Update. 2009;4(1):42–53.
- Straus M. Canine arthritis treatment: many effective tools can help in the fight against canine arthritis. The Whole Dog J. 2007;10(3). [article]
- Silver, Robert J. Integrative Oncology: Blending the Best of Conventional with Evidence-Based and Supportive Complementary Therapies. Holistic Veterinary Medicine Club Symposium 2013. Veterinary Information Network.
- Dodds, Jean. Alternative Therapies for Pain Management. Holistic Veterinary Medicine Club Symposium 2013. Veterinary Information Network.
- Berent, Allyson. Urinary Stone Disease in Dogs and Cats: Are Minimally Invasive Alternatives an Option for Your Patient? Atlantic Coast Veterinary Conference 2011. Veterinary Information Network.
- Center, SA. Chronic Canine Hepatitis. Wild West Veterinary Conference 2010. Veterinary Information Network.
- Center, SA. Non-Conventional Therapies for Necroinflammatory & Cholestatic Hepatobiliary Disease. ACVIM 2005. Veterinary Information Network.
- Hesta, M. et al, The effect of vitamin C supplementation in healthy dogs on antioxidative capacity and immune parameters. J Anim Physiol Anim Nutr (Berl).2009 Feb;93(1):26-34. doi: 10.1111/j.1439-0396.2007.00774
- Beigh, SA., et al. Trace minerals status and antioxidative enzyme activity in dogs with generalized demodecosis. Vet Parasitol.2013 Nov 15;198(1-2):180-6. doi: 10.1016/j.vetpar.2013.08.001. Epub 2013 Aug 12. doi: 10.1016/j.vetpar.2013.08.001
- Hishiyama, N. et al. Plasma concentration of vitamin C in dogs with a portosystemic shunt. Can J Vet Res.2006 Oct;70(4):305-7. [paper]
- Winter, J, et al. Antioxidant status and biomarkers of oxidative stress in dogs with lymphoma. J Vet Intern Med.2009 Mar-Apr;23(2):311-6. doi: 10.1111/j.1939-1676.2009.0273
- Brooks, Wendy. Uric Acid Stones and Urate Urolithiasis. The Pet Health Library. VeterinaryPartner.com 03/06/2012, reviewed and revised.