Vitamin A is found in multivitamins, fish oil supplements and organ meats. While toxicity is rare, ingestion of large amounts can cause toxicity, especially in cats. In general, the amount needed to cause toxicity is 10-1000 times beyond the recomended daily dietary requirements for most species, but in a cat especially, that threshold can be reached quickly. Always check with your veterinarian prior to giving any supplement to your companion. Most toxicity occurs acccidentally, such as by dropping one of your own Vitamin A tablets or multivitamins, however feeding large amounts of organ meats and cod liver oil supplements are other primary causes of this particular toxicity, so only give these with guidance from your vet about appropriate thresholds for your pet.