Dog owners often hear about the importance of vitamins, but when it comes to vitamin D, both too little and too much can be dangerous.
Unlike humans, dogs can’t produce vitamin D from sunlight, so they rely entirely on their diet. But how do you know if they’re getting the right amount? And should you ever supplement it?
In this article, I go through and explain how vitamin D works and whether dogs need vitamin D supplementation or not.
Related: Do Dogs Need Vitamin C?
Key Takeaways
What is Vitamin D, and Why Do Dogs Need It?
Vitamin D is an essential nutrient that plays a crucial role in dogs’ health.
It helps the body absorb calcium and phosphorus, which are necessary for strong bones and teeth. Without enough vitamin D, dogs can suffer from bone weakness, muscle issues, and a weakened immune system, making them more vulnerable to illness.
Unlike humans, dogs cannot synthesize vitamin D from sunlight. Instead, they must get it entirely from their diet.
This makes it even more important for dog owners to ensure their pet’s food contains the right amount.
There are two forms of vitamin D:
- Vitamin D2 (ergocalciferol) comes from plant sources, such as mushrooms.
- Vitamin D3 (cholecalciferol) is found in animal-based foods like fish, egg yolks, and liver.
Dogs absorb vitamin D3 far more efficiently than D2, which is why high-quality commercial dog foods include D3 rather than plant-based alternatives.
Since dogs rely solely on their diet for vitamin D, ensuring they receive a properly balanced food is key to avoiding both deficiency and toxicity.
Benefits of Vitamin D
Vitamin D is an important building block for dogs too. It is almost like a hormone that ties together many functions and here is a list of the major benefits:
- Helps phosphate and calcium to absorb better
- Maintains the calcium balance in the system
- Supports bone health
- Supports dental health
- Helps maintain gut health
- Promotes functions of the immune system
Due to the reasons listed above, vitamin D is crucially important for a puppy’s growth. Puppies need vitamin D to develop healthy bones and muscles.
How Do Dogs Get Vitamin D?
Dogs do not produce vitamin D on their own and therefore it’s needed from the diet. Kibble and wet food are labeled as ‘complete feed’ which means that the products are designed to contain all the minerals and nutrients a dog needs daily.
So, if you are feeding a recommended amount of food as instructed in the dog food packaging, your dog is most likely doing fine.
Dogs that are raw fed or are fed 50/50, should take a look at their diets and make sure the daily intake of vitamin D is secured. Next, we will discuss how you can add more vitamin D to your dog’s diet.
Sources of Vitamin D
If you want to boost your dog’s vitamin D intake, try some of these foods:
- Salmon
- Tuna fish
- Swordfish
- Sardines
- Lactose-free yogurt
- Kefir
- Beef liver
- Egg yolk
- Fish oil supplements
I give my cavaliers teaspoon (5ml) of wild fish oil every day.
Note that vegetables contain hardly any vitamin D. Dogs thrive eating animal fats and meat.
Dogs That Need Vitamin D Supplementation
A typical family dog that eats good-quality complete feed such as kibble or wet food doesn’t generally need vitamin D supplements. On the contrary, in 2018 and 2019 FDA reported how some dry dog food contained toxic levels of vitamin D.
But there are situations where supplementation can be beneficial:
- Pregnant and nursing dogs
- Aging dogs
- Working dogs that endure a lot of physical stress
- Dogs that compete in different sports
- Dogs eating raw and 50/50 diets
Symptoms of Vitamin D Deficiency in Dogs
Vitamin D is essential for maintaining strong bones, muscle function, and a healthy immune system.
When a dog doesn’t get enough vitamin D, it can lead to a range of health problems, some of which may not be immediately obvious. Since dogs rely entirely on their diet for vitamin D, deficiencies are more common in dogs fed unbalanced homemade diets or poor-quality commercial foods.
Here are some of the key symptoms of vitamin D deficiency in dogs:
- Weak or brittle bones – Vitamin D helps regulate calcium and phosphorus levels, which are essential for bone health. A deficiency can lead to soft or fragile bones, increasing the risk of fractures. You may notice your dog limping, moving cautiously, or showing signs of joint pain.
- Muscle weakness and lethargy – Dogs with low vitamin D may seem less active or struggle with movements they once handled easily. If your dog is unusually tired, reluctant to play, or has difficulty standing up, a nutrient deficiency could be a factor.
- Poor growth in puppies – Puppies need adequate vitamin D for proper skeletal development. A deficiency can result in stunted growth, bowed legs, or other developmental issues.
- Increased risk of infections – Vitamin D also supports the immune system. If a dog is frequently getting sick, has slow-healing wounds, or struggles to recover from minor illnesses, it could be a sign that their body isn’t getting enough vitamin D to maintain a strong immune response.
If you notice any of these symptoms, consult your veterinarian. They can assess your dog’s diet, run blood tests if needed, and recommend the best course of action to ensure your dog is receiving the right amount of vitamin D.
How Much Vitamin D Per Day For Dogs?
Unlike vitamin C, vitamin D is a fat-soluble vitamin meaning that the excess vitamins won’t be flushed with urine. Fat-soluble vitamins are stored in the body and liver.
Vitamin D absorbs better when consumed with food. Because fat-soluble vitamins are stored in the body, there is a possibility of overdosing.
Recommendations for daily intake of vitamin D vary from country to country. The National Research Council (US) has determined that the daily intake should be 0,275 μg per kilo.
Calculate: Your dog’s weight in kilos x 0,275 = results.
Example; My dog weighs 7,8kg so my calculation is 7,8 x 0,275 = 2,145μg.
For reference, the National Institutes of Health recommends humans take 15 μg of vitamin D per day. That means small dogs’ daily need for this vitamin is almost seven times less than humans.
When comes to big dogs, let’s say dogs of 30-40 kilos, it’s from 8,25μg to 11μg. This means bigger dogs’ daily recommendation for vitamin D is almost the same as what the daily recommendation is for humans.
FAQ
Conclusion
Vitamin D is essential for your dog’s overall health, supporting strong bones, muscle function, and immunity. Since dogs rely entirely on their diet for this nutrient, feeding a well-balanced commercial dog food ensures they get the right amount.
Deficiency is rare in dogs eating properly formulated food but can be a concern for those on unbalanced homemade diets. On the other hand, too much vitamin D—often from accidental supplementation—can lead to toxicity and serious health risks.
If you’re unsure whether your dog’s diet provides enough vitamin D, consult your vet before making any changes. A carefully managed diet is the safest way to maintain optimal health without the risks of deficiency or overdose.
