Vitamin D3 (cholecalciferol) is essential for calcium and phosphorus metabolism, bone mineralization, immune regulation, and muscle function in dogs and cats. Unlike humans, companion animals have limited ability to synthesize vitamin D3 from sunlight due to their skin structure and grooming behaviour — making dietary or supplemental intake the primary source. Deficiency is more common than many owners recognize, particularly in indoor pets eating certain processed diets.
Rx D3 by Rx Vitamins for Pets provides vitamin D3 in a precise, easily administered liquid format. The liquid delivery allows accurate, weight-appropriate dosing — important for a fat-soluble vitamin where the margin between deficiency and excess requires attention. Developed by Rx Vitamins for Pets to NASC quality standards.
Administer as directed by your veterinarian or per product label weight-based dosing. Mix into food or administer directly. Do not exceed recommended dose — vitamin D3 is fat-soluble and accumulates in tissue; toxicity is possible with significant overdose.
Vitamin D3 is one of the most important supplements to get right — both the dose and the monitoring. It is a fat-soluble vitamin that accumulates in body fat and liver tissue, so unlike water-soluble vitamins, excess intake can cause toxicity over time. However, deficiency is also clinically significant and increasingly recognized in veterinary medicine. If your veterinarian has recommended vitamin D3 supplementation based on bloodwork, Rx D3 provides a measurable, reliable liquid dose — but periodic serum 25-hydroxyvitamin D monitoring is advisable for pets on long-term supplementation.
Deficiency is confirmed by a serum 25-hydroxyvitamin D blood test. Symptoms can include muscle weakness, bone pain, immune dysfunction, and poor growth in younger animals. Discuss testing with your veterinarian if you have concerns.
Yes. Dogs and cats utilize D3 (cholecalciferol) more efficiently than D2 (ergocalciferol), making D3 the preferred form for supplementation in veterinary contexts.
Rx D3 Forte contains a higher concentration of vitamin D3 per mL (12.5 µg per dose) for pets with confirmed deficiency or higher supplementation needs as directed by a veterinarian. Standard Rx D3 is for maintenance or lower-dose supplementation.
Check the vitamin D3 content of your multivitamin first to avoid doubling the dose unintentionally. Most comprehensive multivitamins already contain some vitamin D3.
