Vitamin D3 and K2 Supplements: Take Them Together?

Yes, you can take vitamin D3 and K2 supplements together, ideally with a meal that contains fat, which raised vitamin D3 absorption by 32% in a randomized test¹. The catch is the evidence: a 2-year trial of the pair in 365 men found no slowing of heart valve calcification².

Vitamin D helps you absorb calcium, and vitamin K is the cofactor that activates calcium-binding proteins in bone and artery walls^{3, 4}. That is the logic behind the combination. Anyone on warfarin should not add K2 without their prescriber, because as little as 10 mcg a day shifted blood clotting tests in some people⁵. For what each vitamin does on its own, see our vitamin D and vitamin K2 evidence pages.

Yes, there is no known reason to separate them, and the largest trial of the pair gave both together, every day, for 2 years². In that trial, deaths and cardiovascular events were no more common on the supplements than on placebo².

The rationale is about calcium handling. Vitamin D increases calcium absorption from the gut, and it also helps regulate immune function and cell growth³. Vitamin K activates proteins such as osteocalcin in bone and matrix Gla protein in vessel walls, which only work once vitamin K has modified them^{4, 6}. A 2017 review argued that vitamin D raises production of these proteins, so the two may work as a pair⁷. That review also noted that few trials have tested the pair on heart outcomes⁷.

Combination products pair vitamin D3 (cholecalciferol) with K2, either as MK-7 (menaquinone-7), a form with a very long half-life, or as MK-4^{4, 6}:

• Vitamin D3: the form your skin makes from sunlight; vitamin D from sun, food or pills must be converted in the liver and kidney before it works³.
• MK-7: peaks in blood about 4 hours after a dose and builds up to levels 7 to 8 times higher than vitamin K1 with daily use⁶.
• MK-4: a short-chain K2, used at a 45 mg daily dose in an older bone trial⁸.

The honest answer is that the benefit of the combination over vitamin D alone is unproven. The evidence is limited: one small bone trial was positive, and the largest trial of the pair, on heart valves and arteries, was neutral^{8, 2, 9}.

For bones

The trial results on bone point in different directions^{8, 10, 11, 12}:

• The pair, 92 women with osteoporosis (21 on both): a vitamin D3 analogue plus 45 mg of MK-4 raised lumbar spine density more than either alone over 2 years⁸. Those were prescription-strength forms, not the vitamins in retail softgels.
• Vitamin D alone, 25,871 adults: 2,000 IU a day for a median of 5.3 years did not lower total, hip or non-vertebral fractures in people not selected for deficiency¹⁰.
• Vitamin K alone, 36 trials: a 2019 meta-analysis found no clear effect on bone density or vertebral fractures; clinical fractures may fall, but the evidence was not strong enough to confirm it¹¹.
• MK-7 alone, 244 postmenopausal women: 180 mcg a day for 3 years slowed bone loss at the spine and femoral neck (hip), but not at the total hip¹².

Read more on vitamin K2 for bone density and vitamin D for bone density, or browse the bone health hub¹².

For arteries and the heart

Cardiovascular results are mostly neutral^{2, 9, 13, 14, 15}:

• AVADEC, 365 men aged about 71: 720 mcg MK-7 plus 25 mcg (1,000 IU) vitamin D for 24 months did not slow aortic valve calcification, valve narrowing or artery calcification².
• Same trial, 304 men without heart disease: coronary calcium rose by 203 vs 254 units, a difference that was not significant. Heart attacks, artery-opening procedures and deaths, counted together, were fewer on the pair (1.9% vs 6.7%), a result the authors called hypothesis-generating⁹.
• MK-7 alone, 244 postmenopausal women: 180 mcg a day for 3 years reduced arterial stiffness, mostly in women who started stiff¹³. A post hoc analysis of a 1-year trial in 165 women found a similar effect after menopause¹⁴.
• MK-7 alone, 68 people with type 2 diabetes: 360 mcg a day for 6 months did not reduce calcification on CT, and one scan type trended the wrong way¹⁵.

See vitamin K2 for arterial flexibility and the heart health hub for the full evidence¹³.

Not at normal doses, as far as the evidence shows. Soft-tissue calcification, including in coronary vessels and heart valves, occurs in extreme cases of vitamin D toxicity, which is almost always caused by excessive supplement use³.

Toxicity usually comes with blood 25(OH)D above 150 ng/mL and blood calcium above 11.1 mg/dL³. US experts judged signs of toxicity unlikely below 10,000 IU a day. But they noted that even intakes under the upper limit (4,000 IU for adults) might have adverse effects over time, and advised avoiding blood 25(OH)D above about 50 to 60 ng/mL³.

The idea that K2 shields arteries from vitamin D has only been tested indirectly. In AVADEC, the pair lowered inactive matrix Gla protein, the marker K2 is meant to fix, yet valve calcification progressed just as fast as on placebo². So adding K2 is not a licence for high-dose vitamin D.

Take them with your largest meal, or any meal that contains fat; the time of day matters less than the food^{1, 16}.

• With fat: in 50 older adults given 50,000 IU of D3, peak blood vitamin D3 was 32% higher after a meal with 30% of calories from fat than after a fat-free meal¹.
• With the largest meal: in 17 clinic patients who were not responding to treatment, moving the dose to the biggest meal raised 25(OH)D by an average of 57% over 2 to 3 months¹⁶. It had no control group.
• Morning or night: we found no trial comparing the two. MK-7 has a very long half-life, so blood levels stay steady whatever the hour⁶.

Some vitamin D is absorbed even without fat, so a missed meal is not a wasted dose³. Pick a meal you never skip, such as dinner, and keep it consistent.

For most adults, intake from food plus supplements of 600 to 800 IU of vitamin D and 90 to 120 mcg of vitamin K meets the official targets^{3, 4}. Many combination products give far more.

• Vitamin D, adults 19-70: 600 IU (15 mcg) a day; over 70, 800 IU (20 mcg)³.
• Vitamin D upper limit: 4,000 IU (100 mcg) a day for anyone 9 and older. It is lower for younger children: 1,000 IU up to 6 months, 1,500 IU at 7 to 12 months, 2,500 IU at 1 to 3 years and 3,000 IU at 4 to 8 years³.
• Vitamin K adequate intake: 120 mcg for men and 90 mcg for women; no upper limit was set because no harm has been reported from food or supplements, though it has a potentially dangerous interaction with warfarin (see below)⁴.
• K2 doses in trials: 180 mcg MK-7 for bone and stiffness, 360 mcg in diabetes and 720 mcg in AVADEC^{12, 15, 2}.

More vitamin D is not better for bone. In a 3-year trial of 311 healthy adults, 4,000 or 10,000 IU a day led to slightly lower forearm bone density than 400 IU, with no gain in bone strength¹⁷. The common 5,000 IU products are above the upper limit³.

Food rarely closes a real gap: one large egg has 44 IU of vitamin D, so two eggs give 88 IU, and fatty fish and fortified foods are the main dietary sources³.

A serum 25(OH)D blood test tells you where you start. Levels of 20 ng/mL or more are sufficient for most people, and deficiency risk rises below 12 ng/mL³. Results can vary between lab assays³. Real deficiency, more common in people who are vegan, have a milk allergy or get little sun, shows up as bone pain and deformity, muscle weakness and pain, muscle spasms and dental problems³. See vitamin D for deficiency for repletion evidence.

Too much vitamin D raises blood calcium, and high calcium causes these signs³:

• nausea, vomiting and loss of appetite;
• muscle weakness and pain;
• excessive thirst, frequent urination and dehydration;
• confusion or other mental changes;
• kidney stones.

Severe cases can cause kidney failure and abnormal heart rhythms³. If you have these symptoms while taking high doses, stop the supplement and see a doctor promptly to have your blood calcium and 25(OH)D checked.

People on warfarin-type blood thinners are the main group who should not take K2 without medical advice; a few others need to watch the vitamin D side^{4, 3}.

• Warfarin and other vitamin K antagonists: these drugs work by blocking vitamin K, so sudden changes in intake can raise or lower their effect⁴. In 18 volunteers on acenocoumarol, a warfarin-like drug, 10 mcg of MK-7 a day lowered the INR in a clinically relevant way in at least 40%, and 45 mcg cut the group INR by about 40%; the researchers concluded that people on these drugs should avoid MK-7 supplements⁵. For scale, the MK-7 trials above used 180 to 720 mcg a day^{12, 2}.
• Statins: high vitamin D intakes might reduce the potency of atorvastatin, lovastatin and simvastatin³. In 16 patients on atorvastatin, 800 IU a day lowered drug levels, yet LDL cholesterol fell from 97 to 83 mg/dL¹⁸.
• Thiazide diuretics: these water pills, such as hydrochlorothiazide, cut the calcium lost in urine, so taken with vitamin D they might push blood calcium too high, especially in older adults and people with reduced kidney function or an overactive parathyroid gland (hyperparathyroidism)³.
• Calcium supplement users: taking calcium with vitamin D may increase the risk of some adverse effects. In a 7-year trial of 36,282 postmenopausal women, adding 1,000 mg of calcium and 400 IU of vitamin D a day raised the risk of kidney stones by 17%³.
• Kidney disease, kidney stones or high blood calcium: vitamin D excess causes high blood and urine calcium and kidney stones, and kidneys that are not working well may not convert vitamin D to its active form. Ask your doctor first if you have kidney disease, kidney stones or a history of high calcium³.
• Orlistat users: the weight-loss drug reduces absorption of fat-soluble vitamins, including vitamins D and K, and taken with warfarin it might lengthen clotting time^{4, 3}.

The vitamin D part may help one kind of vertigo, but no trial has tested K2 for it. In benign paroxysmal positional vertigo (BPPV), checking vitamin D and giving it with calcium to people with low levels reduced repeat attacks¹⁹.

• Randomized trial, 1,050 patients: those with levels under 20 ng/mL took 400 IU of vitamin D and 500 mg of calcium carbonate twice daily for a year; recurrences fell from 1.10 to 0.83 per person-year¹⁹.
• Meta-analysis, 5 trials and 1,250 people: vitamin D cut the risk of recurrence (relative risk 0.37), though four of the five trials were not randomized²⁰.

See vitamin D for vertigo and vitamin D for dizziness for the full evidence²⁰.

A simple decision rule, based on the trials above^{3, 4, 5, 1}:

• If you take warfarin: skip K2 unless your anticoagulation clinic agrees and monitors you.
• If you want vitamin D: 600 to 800 IU meets the adult target, and a D3-only product works; adding K2 is optional.
• If you choose the combination: take it with dinner or another meal with fat, and keep total vitamin D at or below 4,000 IU unless prescribed.
• If you take a thiazide water pill, have kidney disease or have had high blood calcium: ask your doctor before starting vitamin D.
• For a child under 9: the vitamin D upper limit is lower, 1,000 to 3,000 IU depending on age, so check the dose before giving any product.
• If you think you are low: get a 25(OH)D blood test first and follow your clinician's repletion plan.

Supplements in this guide

• Vitamin D
• Vitamin K2
• Vitamin K1

Related conditions

• Vitamin D Deficiency
• Osteoporosis
• Vertigo Disorder

We searched PubMed for systematic reviews and randomized trials of vitamin D and vitamin K2 taken together and separately, plus interaction studies with anticoagulants and statins, and read the NIH Office of Dietary Supplements fact sheets on vitamin D and vitamin K. We read 18 study abstracts and cited all of them, prioritizing randomized trials and meta-analyses in adults. The main gap: only a handful of trials test the pair itself, mostly in older adults, and none we found measured fractures as the main outcome. Researched and written 13 October 2026.

1. Dawson-Hughes B, et al. Dietary fat increases vitamin D-3 absorption. J Acad Nutr Diet. 2015;115(2):225-230. doi:10.1016/j.jand.2014.09.014
2. Diederichsen ACP, et al. Vitamin K2 and D in Patients With Aortic Valve Calcification: A Randomized Double-Blinded Clinical Trial. Circulation. 2022;145(18):1387-1397. doi:10.1161/CIRCULATIONAHA.121.057008
3. National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/
4. National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/
5. Theuwissen E, et al. Effect of low-dose supplements of menaquinone-7 (vitamin K2 ) on the stability of oral anticoagulant treatment: dose-response relationship in healthy volunteers. J Thromb Haemost. 2013;11(6):1085-92. doi:10.1111/jth.12203
6. Schurgers LJ, et al. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. 2007;109(8):3279-83. doi:10.1182/blood-2006-08-040709
7. van Ballegooijen AJ, et al. The Synergistic Interplay between Vitamins D and K for Bone and Cardiovascular Health: A Narrative Review. Int J Endocrinol. 2017;2017:7454376. doi:10.1155/2017/7454376
8. Iwamoto J, et al. Effect of combined administration of vitamin D3 and vitamin K2 on bone mineral density of the lumbar spine in postmenopausal women with osteoporosis. J Orthop Sci. 2000;5(6):546-51. doi:10.1007/s007760070003
9. Hasific S, et al. Effects of Vitamin K2 and D Supplementation on Coronary Artery Disease in Men: A RCT. JACC Adv. 2023;2(9):100643. doi:10.1016/j.jacadv.2023.100643
10. LeBoff MS, et al. Supplemental Vitamin D and Incident Fractures in Midlife and Older Adults. N Engl J Med. 2022;387(4):299-309. doi:10.1056/NEJMoa2202106 Our study summary.
11. Mott A, et al. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Osteoporos Int. 2019;30(8):1543-1559. doi:10.1007/s00198-019-04949-0 Our study summary.
12. Knapen MH, et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. 2013;24(9):2499-507. doi:10.1007/s00198-013-2325-6 Our study summary.
13. Knapen MH, et al. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial. Thromb Haemost. 2015;113(5):1135-44. doi:10.1160/TH14-08-0675 Our study summary.
14. de Vries F, et al. Effects of One-Year Menaquinone-7 Supplementation on Vascular Stiffness and Blood Pressure in Post-Menopausal Women. Nutrients. 2025;17(5). doi:10.3390/nu17050815
15. Zwakenberg SR, et al. The effect of menaquinone-7 supplementation on vascular calcification in patients with diabetes: a randomized, double-blind, placebo-controlled trial. Am J Clin Nutr. 2019;110(4):883-890. doi:10.1093/ajcn/nqz147 Our study summary.
16. Mulligan GB, et al. Taking vitamin D with the largest meal improves absorption and results in higher serum levels of 25-hydroxyvitamin D. J Bone Miner Res. 2010;25(4):928-30. doi:10.1002/jbmr.67
17. Burt LA, et al. Effect of High-Dose Vitamin D Supplementation on Volumetric Bone Density and Bone Strength: A Randomized Clinical Trial. JAMA. 2019;322(8):736-745. doi:10.1001/jama.2019.11889
18. Schwartz JB. Effects of vitamin D supplementation in atorvastatin-treated patients: a new drug interaction with an unexpected consequence. Clin Pharmacol Ther. 2009;85(2):198-203. doi:10.1038/clpt.2008.165
19. Jeong SH, et al. Prevention of benign paroxysmal positional vertigo with vitamin D supplementation: A randomized trial. Neurology. 2020;95(9):e1117-e1125. doi:10.1212/WNL.0000000000010343 Our study summary.
20. Jeong SH, et al. Prevention of recurrent benign paroxysmal positional vertigo with vitamin D supplementation: a meta-analysis. J Neurol. 2022;269(2):619-626. doi:10.1007/s00415-020-09952-8