Since dogs can produce vitamin C in their bodies, many dog parents wonder if they need to give their dogs vitamin C tablets. True, dogs can make vit C in their bodies, but if a dog is stressed or sick, their bodies' output of vitamin C can quickly be depleted. In fact, it has been found that stress, both physical (e.g. fever, infections, etc.) and emotional (e.g. stress caused by a change in the environment), is the best-known cause of vitamin C depletion in dogs.