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Vitamin D3 + K2
The Bottom Line
Taking Vitamin D3 and K2 together is not just convenient - it is the physiologically rational way to supplement both.
- Category
- Vitamins & Minerals
- Best form
- cholecalciferol (D3) + menaquinone-7 (MK-7)
- Effective dose
- 1,000-5,000 IU D3 + 90-200mcg K2 (MK-7) daily
- Lab tested
- 5 of 5 products
What Is Vitamin D3 + K2?
Taking Vitamin D3 and K2 together is not just convenient - it is the physiologically rational way to supplement both. The reason comes down to calcium metabolism. Vitamin D3 dramatically increases calcium absorption from the gut. Vitamin K2 activates two critical proteins: osteocalcin (which binds calcium into bone) and Matrix Gla Protein (which prevents calcium from depositing in arteries). Without adequate K2, the extra calcium absorbed from D3 supplementation has nowhere specific to go - and epidemiological data suggests it may contribute to arterial calcification in D3-supplemented individuals who are K2-deficient.
Vitamin D3 alone is well-established. A 2017 Cochrane review (56 trials, 95,286 participants) found vitamin D supplementation reduced all-cause mortality. The US Preventive Services Task Force and most medical societies recognize widespread deficiency - estimated at 35-42% of American adults with blood levels below 20 ng/mL. The evidence for D3 supplementation for bone health, immune function, and all-cause mortality reduction is among the most robust in the supplement literature.
Vitamin K2 adds the cardiovascular protection layer. The Rotterdam Study (4,807 participants) found high K2 intake was associated with 52% lower risk of severe aortic calcification and 57% lower risk of coronary heart disease death. K1 showed no such benefit. This suggests K2's role in vascular calcification prevention is distinct and important, especially when D3 is increasing calcium absorption.
The practical case: if you are taking any meaningful dose of Vitamin D3 (above 1,000 IU), adding K2 is low-risk, low-cost, and biologically sensible. A combined product is simply more convenient than buying two separate supplements. Both are fat-soluble and should be taken with food containing fat.
Does It Work? The Evidence
Bone mineral density and fracture reduction
SupportedCombined D3+K2 RCTs show additive bone effects. Vitamin D3 alone: USPSTF review. K2 alone: Mott et al. 2019 meta-analysis (Osteoporos Int)
Cardiovascular protection (arterial calcification prevention)
Early SignalGeleijnse et al. 2004 Rotterdam Study; Knapen et al. 2015 MK-7 arterial stiffness RCT. D3 alone may worsen arterial calcification without K2.
Immune function support
SupportedD3 component: Martineau et al. 2017 meta-analysis showing reduced acute respiratory infection risk. K2 has minimal immune data.
All-cause mortality reduction
Early SignalBjelakovic et al. 2014 Cochrane review (D3 component); no RCT data specifically for the D3+K2 combination on mortality
| Claimed Benefit | Evidence Level | Key Studies | Our Verdict |
|---|---|---|---|
| Bone mineral density and fracture reduction | Strong | Combined D3+K2 RCTs show additive bone effects. Vitamin D3 alone: USPSTF review. K2 alone: Mott et al. 2019 meta-analysis (Osteoporos Int) | Supported |
| Cardiovascular protection (arterial calcification prevention) | Moderate | Geleijnse et al. 2004 Rotterdam Study; Knapen et al. 2015 MK-7 arterial stiffness RCT. D3 alone may worsen arterial calcification without K2. | Early Signal |
| Immune function support | Strong | D3 component: Martineau et al. 2017 meta-analysis showing reduced acute respiratory infection risk. K2 has minimal immune data. | Supported |
| All-cause mortality reduction | Moderate | Bjelakovic et al. 2014 Cochrane review (D3 component); no RCT data specifically for the D3+K2 combination on mortality | Early Signal |
How to Choose: Forms, Doses & What Matters
Clinical dose: 1,000-5,000 IU D3 + 90-200mcg K2 (MK-7) daily; the combination ensures D3-driven calcium absorption is directed to bones rather than arteries
Best forms: cholecalciferol (D3) + menaquinone-7 (MK-7)
Take the combined supplement with a fat-containing meal - both D3 and K2 are fat-soluble and absorption improves significantly with dietary fat. Once daily dosing is appropriate for both components. The most common and sensible ratio is 1,000-2,000 IU D3 per 100mcg K2, or 5,000 IU D3 with 180-200mcg K2. Do not exceed 4,000 IU D3/day without blood level monitoring. Target serum 25(OH)D level: 40-60 ng/mL. Test your vitamin D levels before starting high-dose supplementation.
Who Should Take Vitamin D3 + K2?
Anyone already taking or considering Vitamin D3 supplementation above 1,000 IU - the K2 addition makes biological sense for protecting arteries. Postmenopausal women (bone density + cardiovascular risk). People over 50 with limited sun exposure or documented D deficiency. Those with elevated risk of arterial calcification (diabetes, metabolic syndrome, hypertension). People eating low-K2 diets (minimal fermented foods or grass-fed animal products).
Who Should Avoid It?
People on warfarin (Coumadin) or other vitamin K antagonist anticoagulants MUST consult their physician before adding K2, as it can significantly affect INR. People with hypercalcemia (elevated blood calcium) should not take high-dose D3 without medical supervision. Sarcoidosis and other granulomatous diseases increase sensitivity to Vitamin D. Do not take high-dose D3 (above 5,000 IU) long-term without periodic blood level monitoring.
Side Effects & Safety
At recommended doses, both D3 and K2 have excellent safety profiles. Vitamin D toxicity (hypercalcemia) requires sustained intake well above 4,000 IU/day - it does not occur from occasional doses or from sunshine. K2 at supplemental doses has no established Tolerable Upper Intake Level. The main safety concern is the K2-anticoagulant interaction (see who should avoid). Signs of Vitamin D toxicity include nausea, weakness, frequent urination, kidney stones, and elevated blood calcium - all very rare at doses below 10,000 IU/day.
Product Scores
5 products scored on evidence quality, third-party testing, cost per effective dose, and ingredient transparency.
The Scorecard: 5 Products Compared
Sports Research Vitamin D3 + K2 (5,000 IU D3 / 100mcg K2)
Sports ResearchHard to beat for value. 360 softgels, coconut oil carrier, correct forms of both D3 and K2. High dose - appropriate for confirmed deficiency or people who have tested and need 5,000 IU.
5,000 IU D3 + 100mcg MK-7 K2 - strong doses of both components in coconut oil carrier for optimal fat-soluble absorption
Non-GMO Project Verified. Third-party tested. Coconut oil carrier ensures fat-soluble absorption without requiring a meal.
$0.05/day - exceptional value for a well-formulated D3+K2 softgel
All ingredients disclosed. MK-7 specified. Cholecalciferol (D3) form confirmed. Coconut oil carrier listed.
5,000 IU D3 + 100mcg MK-7 K2 - strong doses of both components in coconut oil carrier for optimal fat-soluble absorption
Non-GMO Project Verified. Third-party tested. Coconut oil carrier ensures fat-soluble absorption without requiring a meal.
$0.05/day - exceptional value for a well-formulated D3+K2 softgel
All ingredients disclosed. MK-7 specified. Cholecalciferol (D3) form confirmed. Coconut oil carrier listed.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
NOW Foods Vitamin D-3 & K-2 (1,000 IU / 45mcg)
NOW FoodsLowest cost entry point for D3+K2. The 45mcg K2 is below the 90-100mcg seen in most research - consider doubling up or choosing a higher-K2 product.
1,000 IU D3 + 45mcg MK-7 - lower D3 maintenance dose and lower K2 than optimal research doses
NPA GMP audited. NOW has reliable quality track record. Not USP or NSF certified on this product.
$0.05/day - among the cheapest D3+K2 options for a maintenance dose
Both active ingredients disclosed. K2 form (MK-7) specified. Some inactive ingredients in softgel.
1,000 IU D3 + 45mcg MK-7 - lower D3 maintenance dose and lower K2 than optimal research doses
NPA GMP audited. NOW has reliable quality track record. Not USP or NSF certified on this product.
$0.05/day - among the cheapest D3+K2 options for a maintenance dose
Both active ingredients disclosed. K2 form (MK-7) specified. Some inactive ingredients in softgel.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Life Extension Vitamins D3 and K2
Life ExtensionGood lower-dose D3 maintenance option. Multi-form K2 may provide broader coverage across MK-4 and MK-7 benefits.
1,000 IU D3 + 45mcg K2 (MK-4 + MK-7 blend) per softgel - lower D3 dose for maintenance, multi-form K2
Life Extension above-average quality standards. Third-party tested. GMP facility.
$0.10/day for the base dose - reasonably priced for a quality combined product
Both K2 forms (MK-4 and MK-7) disclosed with amounts. D3 form confirmed. Clean olive oil carrier.
1,000 IU D3 + 45mcg K2 (MK-4 + MK-7 blend) per softgel - lower D3 dose for maintenance, multi-form K2
Life Extension above-average quality standards. Third-party tested. GMP facility.
$0.10/day for the base dose - reasonably priced for a quality combined product
Both K2 forms (MK-4 and MK-7) disclosed with amounts. D3 form confirmed. Clean olive oil carrier.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Pure Encapsulations Vitamin D3 + K2
Pure EncapsulationsOptimal dosing for both components with best-in-class quality testing. The choice for those prioritizing quality over cost.
2,000 IU D3 + 180mcg MK-7 - both components at optimal research dosing; 180mcg MK-7 matches the Knapen arterial stiffness RCT
Third-party tested by Eurofins/Silliker. Hypoallergenic. GMP+ certified. Best-in-class quality assurance.
$0.35/day - premium but reasonable for the dose levels and quality
Exemplary label. Every ingredient listed. Hypoallergenic certified. Ideal for those with food sensitivities.
2,000 IU D3 + 180mcg MK-7 - both components at optimal research dosing; 180mcg MK-7 matches the Knapen arterial stiffness RCT
Third-party tested by Eurofins/Silliker. Hypoallergenic. GMP+ certified. Best-in-class quality assurance.
$0.35/day - premium but reasonable for the dose levels and quality
Exemplary label. Every ingredient listed. Hypoallergenic certified. Ideal for those with food sensitivities.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Thorne D-1000 + K2 Liquid
ThorneLiquid format is ideal for those who cannot swallow capsules or want flexible dosing. The MK-4 form provides different but complementary K2 activity vs MK-7 products.
1,000 IU D3 + 200mcg MK-4 K2 per drop - liquid form allows precise dose adjustment
Thorne exceeds industry GMP standards. Third-party tested. NSF program participation. Liquid form avoids excipients from capsule manufacturing.
$0.28/day - premium pricing typical of Thorne, but liquid format has real convenience advantages
Excellent transparency. Liquid form with minimal ingredients. Dose clearly stated per drop.
1,000 IU D3 + 200mcg MK-4 K2 per drop - liquid form allows precise dose adjustment
Thorne exceeds industry GMP standards. Third-party tested. NSF program participation. Liquid form avoids excipients from capsule manufacturing.
$0.28/day - premium pricing typical of Thorne, but liquid format has real convenience advantages
Excellent transparency. Liquid form with minimal ingredients. Dose clearly stated per drop.
Prices checked 2026-03-01. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | Sports Research Vitamin D3 + K2 (5,000 IU D3 / 100mcg K2) Sports Research | NOW Foods Vitamin D-3 & K-2 (1,000 IU / 45mcg) NOW Foods | Life Extension Vitamins D3 and K2 Life Extension | Pure Encapsulations Vitamin D3 + K2 Pure Encapsulations | Thorne D-1000 + K2 Liquid Thorne |
|---|---|---|---|---|---|
| Overall | A- | A- | A- | A- | A- |
| Evidence | A- | A- | A- | A- | A- |
| Quality & Purity | B+ | B+ | B+ | A | A |
| Value | A | A | A- | B | B |
| Transparency | A | B+ | A | A+ | A |
| Cost/Day | $0.05Winner | $0.05 | $0.10 | $0.35 | $0.60 |
| Dose/Serving | 5000IU | 1000IU | 1000IU | 2000IU | 1000IU |
| Form | cholecalciferol D3 + menaquinone-7 MK-7 | cholecalciferol D3 + menaquinone-7 MK-7 | cholecalciferol D3 + MK-4 + MK-7 blend | cholecalciferol D3 + menaquinone-7 MK-7 | cholecalciferol D3 + menaquinone-4 MK-4 |
| Third-Party Tested | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes |
| Proprietary Blend | No | No | No | No | No |
Frequently Asked Questions
Do I need to take K2 with Vitamin D3?
You do not strictly need to, but the combination is biologically rational and recommended by most integrative medicine practitioners. Vitamin D3 increases calcium absorption. Without K2 to activate osteocalcin and Matrix Gla Protein, that extra calcium can accumulate in arteries rather than bones. While RCT evidence specifically showing that adding K2 to D3 reduces cardiovascular risk is still accumulating, the mechanism is clear and K2 supplementation carries essentially no risk.
What is the right ratio of D3 to K2?
No precise ratio has been validated in RCTs. Common practical recommendations are 100mcg K2 per 1,000-2,000 IU D3. For someone taking 5,000 IU D3, 180-200mcg MK-7 K2 is a reasonable target. Most combination products aim for roughly this balance.
Should I take D3+K2 as one pill or separately?
A combined product is convenient and slightly cheaper than buying both separately. The downside is that you lose flexibility to adjust D3 and K2 doses independently. If you need a high D3 dose (5,000 IU+) but only 100mcg K2, finding a product with exactly that ratio may be difficult. In that case, buy a D3-only product and a separate K2 product.
How do I know how much Vitamin D to take?
The best approach is to test your serum 25(OH)D level first, then supplement accordingly to reach 40-60 ng/mL. For people with no data, 1,000-2,000 IU D3 daily is appropriate as a maintenance dose for most adults. Those with known deficiency (below 20 ng/mL) often need 3,000-5,000 IU daily under monitoring. Retest after 3 months of supplementation.
What time of day should I take D3+K2?
Take with a fat-containing meal for best absorption. Breakfast, lunch, or dinner all work. Some people find vitamin D slightly activating and prefer morning dosing, while others have no preference. The most important factor is consistency and ensuring the meal contains at least some fat.
Sources
- Geleijnse JM, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: the Rotterdam Study. J Nutr. 2004;134(11):3100-3105.
- Knapen MH, et al. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. Thromb Haemost. 2015;113(5):1135-1144.
- Bjelakovic G, et al. Vitamin D supplementation for prevention of mortality in adults. Cochrane Database Syst Rev. 2014.
- Martineau AR, et al. Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and individual participant data meta-analysis. BMJ. 2017;356:i6583.
- NIH Office of Dietary Supplements. Vitamin D Fact Sheet for Health Professionals. Updated 2023.
- Mott A, et al. Effect of vitamin K on bone mineral density and fractures in adults. Osteoporos Int. 2019;30(8):1543-1559.
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products discussed on this page are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.