Supplements · Bone & heart
Vitamin D3 and K2: dosage, benefits, and why women take them together
Vitamin D3 helps you absorb calcium. Vitamin K2 (specifically MK-7) directs that calcium into bones and teeth instead of arteries and soft tissue. Taken separately, D3 supplementation without K2 may raise concerns about vascular calcification — which is why serious formulations pair them.
Why the combination matters in menopause
Estrogen loss accelerates bone resorption and increases arterial stiffness — two problems that D3/K2 address in opposite tissues. Trials of MK-7 (180 mcg/day) in postmenopausal women show reduced age-related bone loss and improved arterial elasticity at 3 years.
Getting the dose right
Baseline 25(OH)D under 30 ng/mL is common in women over 40. Correction typically requires 4,000–5,000 IU D3 daily for 8–12 weeks, then a maintenance dose of 2,000 IU. Retest after 90 days.
What to avoid
Skip D2 (ergocalciferol) — less bioavailable than D3. Skip synthetic K1-only supplements for bone goals. Look for MK-7 sourced from natto fermentation with a stated microgram amount, not a proprietary blend.
Frequently asked questions
What is the best D3/K2 dosage?
For most menopausal women: 2,000–5,000 IU vitamin D3 and 90–180 mcg K2 (MK-7 form) daily, taken with a fat-containing meal.
Why take D3 with K2?
D3 boosts calcium absorption; K2-MK7 activates matrix Gla protein and osteocalcin, which direct calcium into bone and away from arteries.
Is MK-4 or MK-7 better?
MK-7 has a much longer half-life (~72 hours vs ~1 hour for MK-4), making once-daily dosing effective.
Can you take too much vitamin D?
Yes. Chronic intake above 10,000 IU/day can cause hypercalcemia. Test 25(OH)D and target 40–60 ng/mL.
Does D3/K2 interact with blood thinners?
K2 can affect warfarin dosing. Talk to your clinician before starting if you take anticoagulants.
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Medically reviewed by Kindr Health Clinical Team · Last reviewed 2026-06-19. Compounded medications are prepared by FDA-registered 503A pharmacies and are not FDA-approved drug products.