Vitamin
Vitamin K2
Vitamin K2 requires 90 mcg daily for adult women and 120 mcg for men. It has 1 severe interaction, notably with Vitamin K2 (MK-7).
What Vitamin K2 does
Directs calcium into bone and away from arteries by activating osteocalcin and matrix Gla protein.
No established UL. RDA is expressed as vitamin K1 equivalents. Contraindicated with warfarin.
How much you need
| Measure | Adult male | Adult female |
|---|---|---|
| Recommended intake | 120 mcg | 90 mcg |
| Upper intake level | None established | |
| Typical supplement dose | 90-180 mcg · 1 cup | |
Interactions involving Vitamin K2
4 sourced rules| Pair | Severity | Mechanism | Action |
|---|---|---|---|
| Vitamin K2 (MK-7) × Warfarin | Severe | Warfarin blocks vitamin K epoxide reductase. Adding vitamin K restores clotting factor synthesis and directly antagonises the drug, which can drop the INR into a clot-risk range. | Do not start vitamin K1 or K2 without telling your prescriber. If you take it, the dose must stay consistent and the INR must be monitored.Source |
| Leafy greens × Warfarin | Moderate | Vitamin K1 from leafy greens competes with warfarin. The risk is variability more than the amount: a sudden jump in intake lowers the INR. | Keep your leafy-green intake consistent week to week rather than avoiding greens entirely.Source |
| Calcium citrate × Leafy greens | Mild | Spinach is high in oxalate, which binds calcium in the gut and makes that plant calcium largely unavailable. | Do not count spinach as a calcium source. Take supplemental calcium away from high-oxalate meals.Source |
| 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 |