There has been an increasing number of voluntary recalls from pet food companies due to excess Vitamin D.  Increased awareness and accountability are responsible for the recall frequency more than an actual increase in incidents.  The recalls have applied to virtually all animals at one time or another, including dogs, cats,  livestock, guinea pigs, birds, primates and fish.  Unfortunately, pet parents aren’t usually provided with details about the dangers and symptoms of excess Vitamin D.

There is also an increasing number of pet parents opting to make their own pet food.  Vitamin D deficiency is a concern in homemade pet diets and supplementation is common.  It’s important that pet parents be aware of the dangers of over-supplementation so they will monitor intake accordingly.

The problem with Vitamin D

Vitamin D is a fat soluble vitamin, which means excesses are not excreted and hypervitaminosis will occur if too much is ingested.

The threat of Vitamin D overdose is minimal through a natural, balanced diet and adequate light exposure.  The highest risk comes from synthetic Vitamin D supplementation, either through pet food or from vitamin supplements administered by pet parents. Natural fish oil and liver supplements may also pose a danger in very high doses.  The safe range may be up to 10 times the daily recommendation and short term excesses may not have any negative impact unless extreme.  The most common concern over elevated levels of Vitamin D in pet food is due to the long term effects (more than a couple of months).

The level of Vitamin D toxicity is subject to the type of Vitamin D.  For example, Vitamin D3 (used in rodenticides) has been proven to be more toxic than Vitamin D2 in many species. Toxicity is also increased when Vitamin E is combined with elevated levels of dietary phosphorus and calcium, and reduced with lower levels of phosphorus and calcium.

There is an increased danger to certain pet species that are prone to Vitamin D toxicosis, such as Macaws and some other avian species. Pet fish and other aquatic pets with diets based largely on whole fish may be at a higher risk Vitamin D toxicosis from synthetic supplementation.  This is especially true in manufactured fish food that typically over-fortifies to compensate for vitamin loss in the water column.  Growing and senior animals are also more vulnerable.

What happens?

When excess Vitamin D is consumed it results in ‘hypervitaminosis D’. It can have a variety of negative effects associated with high concentration of calcium in the blood from bone resorption and increased absorption of calcium in the intestines.  The pathological effect is soft tissue calcification, cellular degeneration and inflammation.  Deaths in cats and dogs caused by hypervitaminosis D is most commonly due to chronic renal failure.

Hypervitaminosis D specifically effects the:

  • Kidneys
  • Lungs
  • Bones & Joints
  • Pancreas
  • Heart & Arteries
  • Digestive system
  • Muscular system
  • Eyes
  • Teeth
  • Lymph Glands
  • Parathyroid Glands

Symptoms of Vitamin D toxicosis and consequential conditions in pets may include loss of appetite, notable weight loss, increased water intake & urination, diarrhea (may be bloody), vomiting, bone & joint pain, lameness, irregular heartbeat, and depression.  Blood tests will show low phosphate and high calcium in the blood. Symptoms in pet fish may include slow growth, dark coloration, lethargy, and loss of appetite.

Unless a veterinarian recommends synthetic supplements, natural sources of Vitamin D are the safest option.  Sunlight, oily fish, egg yolk and seaweed are all natural sources of Vitamin D.

If you suspect Hypervitaminosis D, see your veterinarian immediately.

Kahn, Cynthia. The Merck Veterinary ManualThe Merck Veterinary Manual. 2010.
Michael Stanford, BVSc, MRCVS. The Effect of UV-B Lighting Supplementation in African Grey Parrots. Avian 2004.
DSM Nutritional Products
Halver, J.E. Fish Nutrition. Second ed. Academic Press, San Diego, CA, USA. 1989.


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18 thoughts on “D Is For DEADLY – The Dangers of Excess Vitamin D in Pet Diets ©

  1. Pet food makers say we can’t give our dogs good nutrition because it takes SO much expertise and then they prove they don’t know anything. I’ll keep making my own pet food.

  2. I’m glad they’re telling us but I wish there was nothing to tell. I hope the vitamin D recall didn’t kill any pets.

  3. I’m getting very tired of recalls but I appreciate the internet for information when it happens. You have a wonderful site here and I hope you never take it down.

  4. We just had our horse food recalled for high vitamin D and I was not happy. I know production lines aren’t perfect but come on! You’re in the food business & you have a high responsibility whether you like it or not. If you can’t handle that….get out of the business.

  5. It’s hard to believe pet food companies can’t even get vitamins right. What else are they doing to our pets if they can’t even get that much right?

  6. I gave up on kibble a couple of years ago and never looked back. They had so many recalls I couldn’t stop worrying. It’s not that hard to make your own basic pet food, it doesn’t have to be fancy.

  7. Thank you very much for the vitamin D info. I’ve seen the recalls but I didn’t know what the problem really was until now. I can’t protect my pets if I don’t know this stuff!

  8. Call me stupid but I didn’t know that ANY vitamin could be overdosed. It just never came up. Thanks for the info.

  9. If dogs are outside enough they shouldn’t need vitamin d supplements at all. Indoor cats, birds and reptiles might need it though.

  10. Excess vit D can be dangerous so pet food manufacturers initiate recalls as a precautionary measure. The use of supplements by pet owners is a big concern because many of them believe more is better but that isn’t the case for vit D and A. Your effort to educate pet owners is exceptional and commendable.

  11. I give our dogs sardines a couple of times each week and of course they also go outside a lot.

  12. The more I learn about manufactured vitamins the more worried I get. They only give us one part of vitamins so they’re not like natural food, no wonder they’re toxic.

  13. Thank you very much for clarifying this issue. Vitamin D from lighting is the best and safest way in my opinion.

  14. Is this true? Before they also said that too much sun exposure is bad for us and can cause skin cancer but these days they said vitamin d is vital to our health and can be the answer in lots of health problems. Maybe it’s the same thing with pets. If vitamin d has a good role in human body for sure it will be the same for pets. i want to see more evidence before I’m going to believe this study.

    • Vitamin D is essential for good health in pets like it is in humans. The problem is when too much vitamin D is ingested because it’s a fat soluble nutrient. It builds up in the system until it reaches toxic levels. How much is too much is being debated, but the fact that too much is toxic isn’t in question.

  15. Very well explained, I didn’t know it was so dangerous. The pet food companies make it sound like it’s no big deal. I’d rather take my chances designing my own diet for my pets.

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