Vitamin D is a fat-soluble vitamin which means that when it is ingested to excess, it is not promptly excreted in urine and is, instead, stored in fat and hepatic tissues.
The FDA (Food and Drug Administration) has been analyzing the presence of potentially toxic levels of Vitamin D in various dry pet foods, following notification that some dogs eating dry food experienced Vitamin D toxicity. Signals described included vomiting, hyperoxia, polyuria, polydipsia, ptyalism and/or loss of weight.
A veterinarian suspecting Vitamin D toxicity should carry out a complete anamnesis, checking for feeding details and access to cholecalciferol rodenticides (other possible etiology, generally associated to acute signs, contrarily to diet-related cases). A urinalysis should also be performed and blood samples taken to evaluate calcium, phosphorus and Vitamin D. If levels are high, it is consistent with the presence of this toxicosis.
If Vitamin D toxicity is linked to food, you should advise the pet owner to retain the food in its original packaging and keep it in a secure place. Ask the owner for the lot number so that you can report it to the FDA and/or the local entity responsible for these matters in your region.
The FDA has created a list of products already recalled for this problem and some of the brands concerned have produced press releases which may be helpful.
Please bear in mind that very high amounts of Vitamin D can lead to kidney failure and even death so monitoring your patients’ diets is a must.
FDA Alerts Pet Owners About Potentially Toxic Levels of Vitamin D in Several Dry Pet Foods. Acedido a 16/12/2019, em https://www.fda.gov/animal-veterinary/news-events/fda-alerts-pet-owners-about-potentially-toxic-levels-vitamin-d-several-dry-pet-foods
Vitamin D Toxicity in Dogs. Acedido a 16/12/2019, em https://www.fda.gov/animal-veterinary/animal-health-literacy/vitamin-d-toxicity-dogs