#1 Pharmacist Recommended‡ USP - Dietary Supplement Verified D3 is the Body's Preferred Form of Vitamin D Supports Bone, Teeth, Muscle and Immune Health Vitamin D Supplement Supports Bone, Teeth, Muscle and Immune Health Vitamin D3 is more effective than vitamin D2, at raising and maintaining adequate levels of circulating vitamin D in the body. ‡Based on pharmacy times survey of pharmacists recommending letter vitamin supplements.