Best Vitamin D+K Supplements (2026)

Vitamin D3 increases calcium absorption from food, but without K2, that calcium may deposit in arteries and soft tissues rather than bones. Vitamin K2 activates osteocalcin (which pulls calcium into bones) and matrix GLA protein (which prevents arterial calcification). This is especially important at higher D3 doses above 2,000 IU daily.

MK-4 and MK-7 are both forms of vitamin K2, but MK-7 has a much longer half-life (about 72 hours vs 4-6 hours for MK-4). This means MK-7 maintains more consistent blood levels with once-daily dosing. MK-7 is also effective at lower doses (100-200mcg vs 15-45mg for MK-4). Most D3+K2 supplements use MK-7 for these reasons.

Most experts recommend 100-200mcg of K2 (MK-7) per day when taking 2,000-5,000 IU of D3. At higher D3 doses (10,000 IU), some practitioners suggest 200-300mcg of K2. There is no established tolerable upper limit for K2 — it has not shown toxicity even at high doses in clinical studies. The important thing is to include some K2 rather than debating the exact amount.

Vitamin K2 can interfere with warfarin (Coumadin) and other vitamin K antagonist blood thinners by counteracting their mechanism. If you are on warfarin, do NOT take K2 without your doctor's approval and INR monitoring. Direct oral anticoagulants (DOACs) like apixaban and rivarelbatan work differently and are generally not affected by K2, but still consult your doctor.

The richest dietary source of K2 (MK-7) is natto (Japanese fermented soybeans) — a single serving provides ~1,000mcg. Other sources include gouda cheese (~75mcg per 100g), egg yolks (~32mcg per yolk), chicken liver, and grass-fed butter. Most Western diets provide only 10-30mcg of K2 daily, well below the 100-200mcg recommended for optimal bone and cardiovascular health.

Take D3+K2 with your largest or fattiest meal of the day, regardless of time. Both are fat-soluble and absorption increases up to 50% with dietary fat. Some people find high-dose vitamin D mildly energizing and prefer morning dosing, but there is no clinical evidence that timing matters. Consistency with a fat-containing meal is what matters most.

At 2,000 IU daily, most people see meaningful increases in serum 25(OH)D within 4-6 weeks, with full steady-state levels reached at 8-12 weeks. Higher doses (5,000 IU) raise levels faster but should be monitored with blood work. Get tested before starting and retest after 8-12 weeks to determine if your dose needs adjustment.