In nature, felids typically obtain small amounts of vitamin C from animal tissues, and that background intake is usually sufficient alongside the cat’s own synthesis (Sun M, 2024). In modern homes, most complete-and-balanced commercial diets are designed to meet nutrient needs without requiring add-ons. That’s why supplementation of vitamin C is generally not necessary for cats eating a balanced diet (Sun M, 2024).
The nuance is that “balanced” has a real definition. If a cat is eating an incomplete homemade diet, a highly selective diet, or a rotating menu with gaps, the question becomes broader than vitamin C alone. In those cases, a veterinarian can help evaluate the whole nutrient picture rather than guessing one bottle at a time.