The importance of vitamin D to our health cannot be understated. Vitamin D is not only essential to our bone and dental health but to our overall well-being. Adequate vitamin D in our bodies protects us from a wide range of medical conditions including cancer, heart disease, infections, and rickets.

For many of us, our pets are family members, and their health is important. But how often have we thought of essential vitamins for our pets? For example, do our precious pets need vitamin D? Absolutely. In fact, all land vertebrates (animals with a backbone) require vitamin D for their health. Without adequate vitamin D, pets may suffer from a variety of serious medical conditions including cancer, heart disease, infections, and rickets. (Do you see a pattern?)

The most natural source of vitamin D for all animals is ultraviolet B (UVB) light from the sun. Mammals, birds, and reptiles are designed to acquire the majority of their vitamin D intake from casual exposure to UVB solar light.

Cats and Dogs
Cats and dogs naturally acquire vitamin D nutrient from UVB sunlight. Unlike humans and reptiles, cats and dogs do not make vitamin D in their skin. When UVB rays strike an animal’s fur, oils in the fur are activated to produce vitamin D. Cats and dogs consume vitamin D when they lick or groom their coats.

Vitamin D’s health value to humans continues to be widely researched. However, fewer scientific studies have been conducted on cats and dogs. Recent examples include:

Researchers at The Royal (Dick) School of Veterinary Studies, University of Edinburgh in Scotland concluded that domesticated cats with mycobacteriosis (bacterial infections that can cause often-fatal lesions, abscesses, ulcers) had significantly lower vitamin D blood serum levels than healthy cats. The study was published in the June 2012 edition of Transboundary and Emerging Diseases.

The College of Veterinary Medicine at Cornell University published a landmark study of vitamin D and canine congestive heart failure in the January/February 2014 issue of the Journal of Veterinary Internal Medicine. The Cornell research team concluded that vitamin D deficiency may be a risk factor for congestive heart failure in dogs. Lead author Dr. Marc Kraus stated, “…supplementing with vitamin D [in dogs with congestive heart failure] in addition to conventional therapy may increase survival time [in these patients]. This should be determined with future studies.”

In another study, Cornell University’s College of Veterinary Medicine examined the association between vitamin D blood serum levels and cutaneous mast cell tumors (MCT) in Labrador retrievers. (Mastocytoma, or MCT, is a disorder caused by excess mast blood cells produced in the bone marrow. MCT may lead to the development of certain cancers. The researchers selected Labrador retrievers because this particular canine breed is predisposed to MCT development.) Published in the October 2011 issue of the British Journal of Nutrition, the research findings suggested that low vitamin D levels may be a risk factor for MCT in Labrador retrievers.

Birds indulge in sunning themselves to maintain their body temperature and to consume vitamin D. Our feathered friends sunbathe in a variety of positions including facing the sun with their feathers spread out for maximum exposure to UVB rays. Birds methodically apply preening oil from the uropygial gland—located near the base of their tail—over their plumes to make vitamin D.

Another way birds absorb vitamin D is through their eyes. Birds enjoy better vision than humans because they can see five spectra (red, blue, green, UVA, and UVB), as opposed to the spectra that we see (red, green, and blue). An additional gland around the bird’s retina (Harderian gland) aids absorption of UV light to help regulate breathing, molting, and circadian cycles as well as migration patterns.

Snakes, turtles, lizards, alligators, and other reptiles inherently sun themselves to warm their cold-blooded bodies and absorb UVB light to acquire their vitamin D fix. However, reptiles in captivity often suffer from vitamin D deficiency. Young pet reptiles frequently develop rickets, and older ones often endure osteoporosis.

What Can We Do to Ensure Our Indoor Pets Get Enough Vitamin D?

Modern lifestyles dictate that our pets live primarily indoors. So how can we ensure that they get enough vitamin D for good health?

UVB Light

The most natural source of vitamin D for all animals is UVB light from the sun. Outdoor mammals, reptiles, and birds acquire the majority of their vitamin D intake from casual exposure to UVB sunlight.

Allow your pets outdoors in direct sunlight, ideally between the hours of 10 am and 2 pm, for about 15 to 20 minutes a few times a week. (If you walk your dog, you also benefit from the sun’s healthy rays.)

While we see pets frequently basking in the moving “sun spot” in our homes, they are only enjoying the warmth of the sun. Since UVB rays cannot sufficiently penetrate glass, animals will not make vitamin D from indirect sunlight.

For domesticated reptiles and birds that are limited to indoors, UVB lamps are available for vitamin D sunning. Only consider UVB bulbs designed for birds or reptiles, and please get your veterinarian’s approval prior to use.


Most commercial pet food is fortified with vitamin D. Read the ingredients labels carefully to ensure that the food contains vitamin D3 (cholecalciferol), the most effective form of vitamin D. Think twice about feeding your pet food that simply states, “Vitamin D” because the vitamin may be an analog of vitamin D that is not as effective as vitamin D3.

Wild-caught fatty fish, liver, egg yolks, and some dairy products may also supply your pet with vitamin D3.


Some people give over-the-counter vitamin D3 supplements to their pets. However, these supplements are designed for human consumption. Too much vitamin D can be harmful to your pet. Please check with your veterinarian before providing vitamin D3 supplements to your pets.


The next time your pet has a check-up with your veterinarian, inquire about getting a vitamin D test for your pet. The simple test called 25(OH)D involves blood serum collection that can be performed as part of a routine blood test. Be sure to understand your pet’s test results and inquire if vitamin D3 supplementation is recommended.

Nature dictates the paramount importance of vitamin D to living creatures–including our pets. I wish great vitamin D health for you and your entire family.

Have general questions about vitamin D? Search the web, peruse vitamin D books, and visit my blog.

Author’s Note: Susan Rex Ryan loves animals. She authored Defend Your life, a book about vitamin D’s amazing health benefits. Defend Your Life recently was selected for a Mom’s Choice Award in recognition of providing “the best in family-friendly media, products and services.”

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