The 4000 IU (100 µg) dose is equal to the upper safe limit of daily intake for adults according to NIH ODS (2024) and EFSA (2023), so it is not intended for unlimited daily use throughout the year. Long-term daily use at the level of 3200-4000 IU has been associated in one meta-analysis of RCTs with approximately a 2.2-times higher relative (though still small in absolute terms) risk of hypercalcemia (Zittermann et al., 2023). We recommend using the product mainly during periods with less sun or in cases of confirmed deficiency, and coordinating long-term use with a doctor, preferably while monitoring blood 25(OH)D levels.

Vitamin K2 is indeed not included in this formula – it is a standalone preparation of pure vitamin D3. Some research shows that the combination of D3 and K2 may further support bone quality more than D3 alone (Kuang et al., 2020), as K2 helps direct calcium into the bones. If you're interested in this, our range also includes combined D3+K2 products. This product makes the most sense if you want a standalone, high-dose vitamin D correction without additional ingredients, or if you're already getting K2 from another source.

The capsule in which the vitamin D3 is enclosed is declared vegan for this product, which distinguishes it from classic gelatin (animal-derived) shells. Cholecalciferol itself is, in most products on the market, obtained from lanolin (sheep's wool), so for full certainty about the origin of the active ingredient it is advisable to check with the manufacturer, as the label does not explicitly state this. An alternative is vitamin D2 (ergocalciferol), which is always of plant origin, but according to evidence is less effective at raising and maintaining serum 25(OH)D than D3 (Tripkovic et al., 2012).

The general recommendation (RDA) for a healthy adult population is 600-800 IU per day (NIH ODS, 2024), so 4000 IU considerably exceeds the basic needs of a healthy individual with sufficient sun exposure. Higher doses, such as this one, are in practice used mainly to correct a confirmed deficiency or for people with very limited sun exposure, with the most reliable way to determine actual need being a laboratory-measured blood 25(OH)D value. If your vitamin D status is unknown, we recommend consulting a doctor before long-term use of such a high dose.