The "normal" dose of vitamin D3 that most people need is in the order of a few hundred International Units per day – roughly 600‑800 IU (about 15‑20 µg) for an average adult. In practice, many clinicians prescribe 1,000‑2,000 IU/day for those with low levels or higher risk, but the basic maintenance requirement sits at about 600–800 IU daily.
