Vitamin D is a critical nutrient for bone health, immune function and calcium regulation. When dietary intake or sunlight exposure is limited, supplements are often used to maintain adequate status. Two supplemental forms are common: vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol). Understanding their origins, metabolism and practical differences helps inform an appropriate choice. Vitamin sources and chemistry Vitamin D2 is produced by plants and fungi when exposed to ultraviolet light; common dietary sources include UV-exposed mushrooms and fortified plant-based foods. Vitamin D3 is synthesized in human skin after sun exposure and is found naturally in some animal foods such as oily fish and egg yolks. Chemically, D2 and D3 differ by a small change in the side chain, which affects how they are metabolized and how long they persist in circulation. Absorption, potency and duration Evidence from randomized and observational studies indicates that vitamin D3 generally raises and maintains serum 25-hydroxyvitamin D concentrations more effectively than vitamin D2. D3 appears to have greater potency and a longer half-life in the bloodstream, which can make it more efficient for correcting deficiency in many individuals. Vitamin D2 is still biologically active after conversion to the same hormonal metabolites as D3, but it may be cleared faster and require more frequent dosing in some cases. How plant-based vitamin D fits in For people following vegetarian or vegan diets, vitamin D2 provides a non-animal option that supports vitamin D status without animal-derived ingredients. When choosing plant-based supplements, consider product certification and manufacturing practices to ensure the formulation meets dietary restrictions. Some manufacturers also produce vegan vitamin D3 derived from lichen; these are less common but offer an alternative for those seeking D3 without animal sources. Practical guidance on dosing and administration Recommended intakes vary by age, health status and region; common adult recommendations range from about 600–800 IU daily, with higher therapeutic doses used under medical supervision for deficiency. Vitamin D is fat-soluble, so taking supplements with a meal that contains some fat can improve absorption. Be aware of potential interactions with medications (for example, some anticonvulsants or glucocorticoids) and medical conditions that affect fat absorption; discuss higher doses or monitoring with a healthcare professional. Choosing between D2 and D3 Choose based on dietary preferences, tolerability and clinical goals. Vitamin D3 may be preferred for its potency and durability in raising serum levels, while vitamin D2 remains a valid option, particularly for vegans or those avoiding animal products. In clinical settings where precise repletion is required, monitoring serum 25(OH)D guides dose adjustments regardless of the form used. Further reading and resources For a focused overview and practical comparison, see [Vitamin D2 vs. Vitamin D3](https://www.topvitamine.com/blogs/news/vitamin-d2-vs-vitamin-d3-key-differences-and-how-to-choose-the-right-one). Additional resources on supplement formulations and brands include Dr. Mercola supplements resource, a placeholder link for other related content Related resource, and a general reference page at Topvitamine homepage. Summary Both vitamin D2 and D3 can support vitamin D status; D3 often shows greater effectiveness in raising serum levels, whereas D2 offers a plant-based alternative. Individual needs, dietary choices and clinical context should guide selection, with laboratory monitoring when needed to ensure adequate status.