Vitamin D3 Benefits: Supports healthy teeth and bones by enhancing the absorption of calcium; supports immune function and cardiovascular health* Optimal Absorption: Vitamin D3 (as cholecalciferol) is more potent and better absorbed than vitamin D2 (or ergocalciferol); research shows vitamin D3 is more effective at raising overall vitamin D levels* Essential Vitamin D: Optimizes performance, muscle strength and mass, and cellular repair, especially for those who work indoors or lack adequate sun exposure to support the body's natural vitamin D production* Third-Party Certified: This product has been third-party tested and certified to verify what's in the package matches what's on the label and to confirm it contains no unsafe levels of contaminants Trusted: Thorne is chosen by champions and trusted by 100+ professional sports teams, a proud partner of U.S. National Teams, and the #1 recommended clinical brand by health-care practitioners (2023 Health-Care Practitioner Seller Survey) For individuals needing high-dose vitamin D supplementation. Since 1984, Thorne has set the standard for the exceptional formulation and quality manufacturing of nutritional supplements. Thorne delivers premium, science-based products, a health diagnostics technology platform, and the latest in medical education. With more than 350 products, Thorne is the most dispensed brand by 30-to 40-year-old health-care practitioners. Thorne is dedicated to improving the health of our community as well as increasing the knowledge of nutritional health and wellness. Since 2012, Thorne has partnered with educational institutes and local charities to donate more than 1M in products and profits.Thorne products do not contain any unnecessary binders, coatings, disintegrants, fillers, or lubricants (including magnesium stearate) that could impair absorption. Thorne adheres to the current Good Manufacturing Practices (cGMPs) and has the highest number of NSF Certified for Sport products which test for more than 200 banned substances for elite athletic competitions.