Palatable Source of Pure Cholecalciferol Rx D3™ contains cholecalciferol, the precursor to Vitamin D3 for all animals. The cholecalciferol is blended with virgin olive oil and diluted sufficiently to enable animals as small as 4 kg to be safely medicated. Recent research studies in dogs, cats and humans have found Vitamin D3 insufficiency highly correlated with a number of difficult-to-treat chronic diseases such as cancer, heart disease, inflammatory bowel disease, renal disease, hyperparathyroidism, and feline tooth resorption. By wellness-checking regularly for serum levels of Vitamin D3, those patients with insufficient levels of Vitamin D3 can be identified and supplemented accurately with RxD3. A monthly follow-up test is recommended to insure safe and adequate dosing, and testing thereafter as recommended by your veterinarian.