Vitamin D3

Why this ingredient is used

Vitamin D3 (cholecalciferol) regulates calcium and phosphorus absorption, which is critical for bone health, shell development in tortoises, and immune function. Dogs and cats cannot synthesise enough vitamin D from sunlight (their fur blocks UVB, and cats lack the relevant skin enzyme entirely), so all commercial pet food must add it. For tortoises and reptiles, D3 supplémentation is essential when they are kept without adequate UVB lighting. Overdosing is dangerous: vitamin D toxicity causes hypercalcemia, kidney failure and death. There have been multiple pet food recalls due to excessive vitamin D3 (2018 Hill's recall affected tens of millions of cans).