Vitamin D3 + K2 Benefits: Why They Work Best Together

Vitamin D3 (cholecalciferol) is often called the “sunshine vitamin” because your skin produces it when exposed to sunlight. It helps your body absorb calcium, which strengthens your bones and teeth.

Vitamin K2 is a lesser-known but equally important nutrient. Unlike vitamin D3, vitamin K2 helps send calcium to your bones instead of your arteries. While both vitamins are great for your health, they work best when taken together. 

Emily Villaseca, Owner & Lead Dietitian at Pass The Chia, offered some insight on how these vitamins work:

“Vitamin D3 and K2 work together to help your body absorb and use calcium properly. Vitamin D increases calcium absorption from your food, and K2 ensures that calcium is directed to the bones and teeth rather than accumulating in arteries and soft tissues, which would result in increased risk for heart disease and kidney stones."

This guide explores how vitamin D3 + K2 co-supplementation can work together to support your overall health. Read on to learn everything you need to know.

The Relationship Between Vitamin D3 and K2

Research shows that vitamin D3 increases intestinal calcium absorption by 30-40% (1). However, this is only part of the story — vitamin D3 and K2 work as a team.

Together, they help regulate calcium in your body, supporting bone strength and cardiovascular health. Vitamin D3 helps your body absorb more calcium into the bloodstream.

Kristin Draayer, MS, RDN, CPT, owner of Nutrition by Kristin, explains how this works. She shares that vitamin K2 doesn’t help absorb Vitamin D3, but works after D3 absorbs calcium. K2 then activates proteins that send calcium to your bones.

Once the calcium is absorbed, it needs to be used properly. Vitamin K2 helps send calcium to your bones, making them stronger. It also activates proteins that help bones absorb calcium and stop it from building up in soft tissues. (2).

Without enough vitamin K2, the "calcium paradox" occurs, which means an imbalance of calcium levels in your bones and arteries (2). Over time, this increases the risk of osteoporosis and cardiovascular disease.

What are the Benefits of Combined Vitamin D3 and K2 Intake?

Dietitian Villaseca says bone is constantly being remodeled, so healthy calcium levels are vital. “Vitamin D3 increases calcium absorption rates from 10–15% to 30–40%, while vitamin K2 acts on several proteins that regulate mineralization and strengthen the bone matrix.” 

Combining vitamin D3 and K2 supplements offers several benefits, including:

1. Stronger Bones

You might think calcium is all you need for stronger bones, but it doesn’t work alone. Your body needs vitamin D3 to absorb calcium and vitamin K2 to direct it to your bones.

Otherwise, calcium may deposit in your soft tissues, leading to weaker bones. Vitamin K2 helps keep your bones strong by boosting bone-building cells (osteoblasts) and slowing down bone loss.

Research shows that taking vitamin K and D together can improve bone mineral density and reduce levels of inactive osteocalcin, which is a marker of poor bone health (3). A study found that D3 + K2 supplements can accelerate bone healing in people with weak bones after spinal surgery.

People who took both vitamins had a higher spine fusion success rate (91.18%) compared to those who only took vitamin D3 and calcium (71.43%) after surgery (4). In addition, co-supplementing with D3 and K2 can decrease the risk of osteoporosis in postmenopausal women, especially when combined with a healthy diet (5). 

2. Better Cardiovascular Health

Besides strengthening bones, taking vitamin D3 and K2 together may also keep your heart healthy by managing calcium levels in your body.

If you don't have enough vitamin D3, your body won’t be able to absorb calcium. As a result, calcium starts building up in your arteries instead of strengthening your bones, increasing your risk of heart disease.

Vitamin K2 helps prevent this by activating and stimulating matrix Gla protein (MGP). This protein stops calcification in soft tissues and arteries, keeping your cardiovascular system healthy.

A study found that low vitamin D and K levels may increase your risk of death from several conditions, especially heart-related diseases (6). However, these findings were not conclusive.

A study found that D3 and K2 didn’t stop artery hardening but reduced a sign of calcium buildup, which may support heart health. (7).

“A deficiency in Vitamin D is also associated with high cholesterol, a major risk factor for heart disease. Vitamin K2 may help prevent calcium deposits in the vascular system, which contribute to the development of heart disease,” adds dietician Villaseca. 

3. Immune System Boost

Research shows vitamin D3 can improve your immunity by helping you fight infections. It can also help prevent excessive inflammation, reducing your risk of prolonged infections (8).

On the flip side, vitamin K2 has also been shown to control inflammation by lowering pro-inflammatory cytokines, which are associated with severe COVID-19 cases (9).

In fact, research has shown that people who took 2000 IU of vitamin D2 and 240 mcg of K2 daily for 24 weeks experienced reduced COVID symptoms, improved gut health, and had better inflammatory markers (10). This suggests that taking D3 + K2 supports your immune system and helps your body recover faster after infections.

4. Improved Metabolic Health

Vitamin D3 and K2 may help regulate blood sugar, improve insulin sensitivity, and reduce inflammation. Both vitamins are helpful for people with type 2 diabetes (T2DM) and metabolic syndrome (MetS).

A study found that taking vitamin K2 (100 mcg) and D3 (1000 IU) daily for 12 weeks can help you manage blood sugar levels (11). People with diabetes in this study gained lower glucose levels, better pancreatic function, and improved insulin sensitivity after taking this combination.

What is the Ideal Intake of Vitamin D3 and K2?

How much D3 + K2 you should take depends on several factors. Here are some rough guidelines.

Recommended Dosage of Vitamin D3

Total vitamin D intake depends on your health, age, and skin tone. If you have a vitamin D deficiency, the recommended daily dosage is 1000 to 2000 IU of vitamin D (12).

For a severe deficiency, your doctor may prescribe a high-dose regimen, such as up to 30,000 IU per week for about six to seven weeks, or a daily dose of 4,000 IU (12). This dosage includes food sources and supplements. 

If you take more than 2000 IU of vitamin D daily, you'll need to monitor your levels every three months. Always take it as directed by your doctor to get the best results.

Recommended Dosage of Vitamin K2

Vitamin K2 comes in two common forms: MK-4 and MK-7. MK-7 is preferred because it stays in your body longer, giving longer-lasting benefits. You’ll often find K2 supplements in soft gels, capsules, or liquid drops. 

General guidelines for vitamin K recommend 120 mcg per day for men and 90 mcg for women, though they don’t specify K2 (13). "There's no official RDA for Vitamin K2, but general recommendations suggest 45-100 mcg per day for overall health and 180-200 mcg per day for bone and heart health," says Villaseca.

Co-supplementation of D3 and K2

There’s no definitive dosage when it comes to taking vitamin D2 and K2 together. However, if your vitamin D levels are above 70 ng/mL, adding vitamin K2 can help regulate calcium. 

Research suggests taking 100 mcg daily or 800 mcg weekly along with vitamin D3 to prevent calcium buildup in your arteries (14). To keep vitamin D at the right level in your body, around 70 IU of vitamin D3 per kilogram of body weight is considered safe (15).

Choosing the Right D3 + K2 Supplement

When choosing a vitamin D3 + K2 supplement, quality and absorption matter. Transparent Labs Natural Vitamin D3 + K2 Softgels offer the ideal blend of 5000 IU D3 and 100 mcg K2 to support your health.

With no artificial sweeteners or colors, Transparent Labs’ formula provides plant-based Vitamin D3 from lichen and MK-7 Vitamin K2 from chickpeas. 

This combination supports immune health, bone strength, and heart function by optimizing calcium use, making it a smart choice for overall wellness. For best results, take one softgel once or twice per day with food.

What are the Side Effects of Taking Vitamin D3 and K2 Together?

While vitamins D3 and K2 are generally safe and well-tolerated, high doses or interactions with medications can cause side effects. Some of the common risks include:

Hypercalcemia Risk

Too much vitamin D3 can raise calcium levels in your body, leading to hypercalcemia (16). As a result, you may experience nausea, kidney problems, fatigue, excessive thirst, and confusion. Having high calcium levels for too long may also cause kidney stones or blockages in blood vessels.

“Toxicity of vitamin K2 is unlikely. The biggest concern is for individuals on blood thinners like warfarin, as Vitamin K affects blood clotting and works against blood thinning medications,” adds Villaseca.

Medication Interactions

If you're on any long-term medication, it's important to check for potential interactions. Interactions may make D3 + K2 less effective and increase your risk of side effects.

Some of these medicines include:

• Blood thinners like warfarin and coumadin. High doses of vitamin K2 may interact with anticoagulants, increasing your risk of blood clotting (14). If you’re on blood thinners, speak to your doctor before taking Vitamin K2. 

• Antibiotics such as cefoperazone may make vitamin K less effective.

• Cholesterol-lowering drugs like cholestyramine can reduce vitamin K2 absorption, affecting calcium regulation.

• Weight-loss medications, such as orlistat, block fat absorption and can stop D3 and K2 from being absorbed properly.

• Thiazide diuretics interact with vitamin D3 and can increase calcium levels in your blood (17).

Contraindications

Some health conditions can cause blood calcium levels. In these cases, taking high doses of vitamin D3 and K2 might be unsafe. Consult your doctor if you have:

• Kidney problems

• Hypercalcemia

• Hyperparathyroidism

• Blood clotting disorders

• Severe liver disease

• Sarcoidosis and other granulomatous diseases (in which the immune system forms clusters of inflammatory cells in the body, usually in the lungs and lymph nodes)

The Bottom Line

Vitamin D supplements help support strong and healthy bones by promoting bone growth and maintaining healthy arteries. Vitamin D3 and K2 work together for better bone and cardiovascular support.

Transparent Labs’ formula is a natural option with no artificial flavoring that can help boost your health. For best results, speak to a healthcare professional before starting any new supplement regime. 

FAQs

1. Can you take vitamin K2 and D3 every day?

Yes, it’s safe to take vitamin K2 and D3 together every. Be sure to take the recommended dose and consult with your doctor, especially if you plan to take high doses.

2. Can D3 and K2 help with weight loss?

Vitamin D3 and K2 may indirectly promote weight loss, but research on this is limited. Low vitamin D has been linked with obesity (18), and some animal studies show that vitamin K2 may improve fat metabolism (19). However, further research is needed to confirm the effects of these supplements on weight management.

3. Should I take vitamin D3 and K2 in the morning or at night?

You can take vitamin D3 and K2 supplements at any time of the day with a meal. However, it’s best to take them in the morning with food containing fats, which can maximize absorption.

References

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2. Mandatori, D., Pelusi, L., Schiavone, V., Pipino, C., Di Pietro, N., & Pandolfi, A. (2021). The Dual Role of Vitamin K2 in “Bone-Vascular Crosstalk”: Opposite Effects on Bone Loss and Vascular Calcification. Nutrients, 13(4), 1222. https://doi.org/10.3390/nu13041222

3. Kuang, X., Liu, C., Guo, X., Li, K., Deng, Q., & Li, D. (2020). The combination effect of vitamin K and vitamin D on human bone quality: a meta-analysis of randomized controlled trials. Food & Function, 11(4), 3280–3297. https://doi.org/10.1039/c9fo03063h

4. Zhang, W., Li, L., Zhou, X., Li, K., Liu, C., Lin, X., Lubisi, N., Chen, J., & Si, H. (2021). Concurrent Treatment with Vitamin K2 and D3 on Spine Fusion in Patients with Osteoporosis-Associated Lumbar Degenerative Disorders. Spine, Publish Ahead of Print. https://doi.org/10.1097/brs.0000000000004309 

5. Rusu, M. E., Bigman, G., Ryan, A. S., & Popa, D.-S. (2024). Investigating the Effects and Mechanisms of Combined Vitamin D and K Supplementation in Postmenopausal Women: An Up-to-Date Comprehensive Review of Clinical Studies. Nutrients, 16(14), 2356. https://doi.org/10.3390/nu16142356 

6. van Ballegooijen, A. J., Beulens, J. W. J., Kieneker, L. M., de Borst, M. H., Gansevoort, R. T., Kema, I. P., Schurgers, L. J., Vervloet, M. G., & Bakker, S. J. L. (2020). Combined low vitamin D and K status amplifies mortality risk: a prospective study. European Journal of Nutrition, 60(3), 1645–1654. https://doi.org/10.1007/s00394-020-02352-8 

7. Diederichsen, A. C. P., Lindholt, J. S., Möller, S., Øvrehus, K. A., Auscher, S., Lambrechtsen, J., Hosbond, S. E., Alan, D. H., Urbonaviciene, G., Becker, S. W., Fredgart, M. H., Hasific, S., Folkestad, L., Gerke, O., Rasmussen, L. M., Møller, J. E., Mickley, H., & Dahl, J. S. (2022). Vitamin K2 and D in Patients With Aortic Valve Calcification: A Randomized Double-Blinded Clinical Trial. Circulation, 145(18), 1387–1397. https://doi.org/10.1161/circulationaha.121.057008 

8. Bychinin, M. V., Klypa, T. V., Mandel, I. A., Yusubalieva, G. M., Baklaushev, V. P., Kolyshkina, N. A., & Troitsky, A. V. (2022). Effect of vitamin D3 supplementation on cellular immunity and inflammatory markers in COVID-19 patients admitted to the ICU. Scientific Reports, 12(1). https://doi.org/10.1038/s41598-022-22045-y 

9. Xie, Y., Li, S., Wu, D., Wang, Y., Chen, J., Duan, L., Li, S., & Li, Y. (2024). Vitamin K: Infection, Inflammation, and Auto-Immunity. Journal of Inflammation Research, 17, 1147–1160. https://doi.org/10.2147/JIR.S445806 

10. Atieh, O., Daher, J., Durieux, J., Abboud, M., Labbato, D., Jhony Baissary, Ziad Koberssy, Ailstock, K., Cummings, M., Funderburg, N., & McComsey, G. (2025). Vitamins K2 and D3 Improve Long COVID, Fungal Translocation, and Inflammation: Randomized Controlled Trial. Nutrients, 17(2), 304–304. https://doi.org/10.3390/nu17020304 

11. Aguayo-Ruiz, J. I., García-Cobián, T. A., Pascoe-González, S., Sánchez-Enríquez, S., Llamas-Covarrubias, I. M., García-Iglesias, T., López-Quintero, A., Llamas-Covarrubias, M. A., Trujillo-Quiroz, J., & Rivera-Leon, E. A. (2020). Effect of supplementation with vitamins D3 and K2 on undercarboxylated osteocalcin and insulin serum levels in patients with type 2 diabetes mellitus: a randomized, double-blind, clinical trial. Diabetology & Metabolic Syndrome, 12(1). https://doi.org/10.1186/s13098-020-00580-w 

12. NHAl-Hashimi, N., & Abraham, S. (2025). Cholecalciferol. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK549768/ 

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15. Hariri, E., Kassis, N., Iskandar, J.-P., Schurgers, L. J., Saad, A., Abdelfattah, O., Bansal, A., Isogai, T., Harb, S. C., & Kapadia, S. (2021). Vitamin K2—a neglected player in cardiovascular health: a narrative review. Open Heart, 8(2), e001715. https://doi.org/10.1136/openhrt-2021-001715

16. Armin Zittermann, Trummer, C., Theiler‐Schwetz, V., & Pilz, S. (2023). Long-term supplementation with 3200 to 4000 IU of vitamin D daily and adverse events: a systematic review and meta-analysis of randomized controlled trials. European Journal of Nutrition, 62(4), 1833–1844. https://doi.org/10.1007/s00394-023-03124-w

17. Wakeman, M. (2021). A Literature Review of the Potential Impact of Medication on Vitamin D Status. Risk Management and Healthcare Policy, Volume 14, 3357–3381. https://doi.org/10.2147/rmhp.s316897

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19. Qu, Z., Zhang, L., Huang, W., & Zheng, S. (2022). Vitamin K2 Enhances Fat Degradation to Improve the Survival of C. elegans. Frontiers in Nutrition, 9. https://doi.org/10.3389/fnut.2022.858481