Vitamin
Vitamin D3
Vitamin D3 requires 600 IU daily for adult women and 600 IU for men. The tolerable upper intake level is 4000 IU. It works best alongside Vitamin D3 softgel and Vitamin D3 softgel.
What Vitamin D3 does
Regulates calcium absorption and bone mineralisation, and supports immune and neuromuscular function.
RDA rises to 800 IU after age 70. Deficiency is common at northern latitudes.
How much you need
| Measure | Adult male | Adult female |
|---|---|---|
| Recommended intake | 600 IU | 600 IU |
| Upper intake level | 4000 IU | |
| Typical supplement dose | 1000-5000 IU · 100 g | |
Interactions involving Vitamin D3
4 sourced rules| Pair | Severity | Mechanism | Action |
|---|---|---|---|
| Vitamin D3 softgel × Vitamin K2 (MK-7) | Synergy | Vitamin D raises calcium absorption and vitamin K2 activates matrix Gla protein, which directs that calcium into bone rather than soft tissue. They are complementary, not redundant. | Take vitamin D3 and K2 together with a fat-containing meal. Typical pairing is 1000 IU D3 per 100 mcg K2.Source |
| Vitamin D3 softgel × Fish oil (EPA/DHA) | Synergy | Both are fat-soluble and require dietary fat for micelle formation and lymphatic absorption. Taken with fat, each improves the other’s uptake. | Take vitamin D3 and fish oil in the same meal that contains at least 10-15 g of fat.Source |
| Vitamin D3 softgel × Avocado / olive oil | Synergy | Dietary fat triggers bile release and chylomicron formation, which vitamin D depends on for absorption. Without fat, uptake can fall by half. | Always take vitamin D3 with a meal containing fat — avocado, olive oil, eggs or fatty fish all work.Source |
| Calcium citrate × Vitamin D3 softgel | Synergy | Vitamin D drives active calcium absorption in the small intestine via calbindin. Without adequate vitamin D, calcium supplementation is far less effective and may not reach bone. | Take calcium with vitamin D3, and keep calcium doses at or below 500 mg at a time for absorption.Source |