Medically reviewed by Lindsay Cook, PharmD
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Vitamin D helps improve calcium absorption, while vitamin K2 ensures that calcium is deposited in the bones rather than in surrounding tissues.
Taking vitamin D and K together may be more effective than taking either alone for bone and heart health.
Taking vitamin K2 with Vitamin D is optional and may not be required for your vitamin D supplements to be effective.
Vitamin D3 and vitamin K2 are often paired in dietary supplements because both nutrients may support bone and heart health. However, many people believe that to see the full benefit of vitamin D, you cannot take it without vitamin K2. Some claim that taking vitamin D without Vitamin K2 could even be dangerous. We spoke to dietitians and nutrition researchers to examine whether these claims are true and whether you really need to take vitamin D and K together.
Why Vitamin D and K2 Are Paired Together
​Vitamin D helps improve calcium absorption, which is important for healthy bones, while vitamin K2 ensures that calcium is deposited in the bones rather than in surrounding tissues.
“These nutrients work together to regulate how calcium is used by the body, as calcium moving out of the blood and into the bone is essential for maintaining healthy circulation,” Eric Ciappio, PhD, RD, and Senior Manager of Nutrition Science at Balchem Human Nutrition & Health, told Health.
Aside from the benefits for bone health, vitamin D and K2 may be paired together to protect the heart. Without adequate vitamin K, calcium may deposit on arterial walls, leading to hardening of the arteries (atherosclerosis).
Is Vitamin D Ineffective Without K2?
Studies suggest that taking vitamin D and K together may be more effective than taking either alone for bone and heart health.
“Nutrients rarely work in isolation, and often depend on one another to help best support health,” Ciappio said.
However, there is currently no official recommendation to always take vitamin D and K supplements together. Moreover, there’s not enough evidence to suggest that vitamin D by itself will work well alone.
​”Vitamin D supplementation without vitamin K2 may still produce positive effects, possibly because vitamin K2 is present in some animal food products,” Lina Begdache, PhD, RDN, and an associate professor at Binghamton University, told Health. However, this explanation remains speculative and has not yet been confirmed in clinical trials.
You may consider taking vitamin D and K together if:
You live with osteoporosis
You are at risk of heart disease
However, talk to your healthcare provider first before starting vitamin D and K2 supplements to make sure they are safe for you.
The Potential Benefits of Taking Them Together
Here are some possible benefits you may get from taking vitamin D and K2 together.
1. May Improve Bone Health
Vitamin D helps your body absorb calcium from food, and vitamin K helps make sure it is deposited in the bones, where your body needs it.
Studies suggest that together, both supplements may help prevent osteoporosis (a condition that weakens the bones).
“Calcium is the most abundant mineral in our body, with 99% of it found in our bones and teeth. The other 1% is stored in our blood and soft tissues, so helping to direct this calcium from our bloodstream into the bones is critical for both the bone and the heart,” said Ciappio.
2. May Reduce Inflammation
Vitamin D and vitamin K3 also have anti-inflammatory effects that may help improve heart health.
Their combined ability to reduce inflammation may also help reduce some long COVID symptoms, particularly fatigue, post-exertional malaise, and body pain. More research in humans is needed to confirm this benefit.
3. May Protect Heart Health
Combined supplementation with vitamin D and K2 also offers protective effects on the heart.
​However, high doses of vitamin D may lead to calcium deposits around the walls of the blood vessels (arteries). Vitamin K, on the other hand, prevents these deposits, preventing arterial stiffness and atherosclerosis (hardening of the arteries).
4. May Lower Blood Sugar
Some emerging evidence suggests that combined supplementation of vitamin K2 and Vitamin D may lower blood sugar levels.
However, these studies were carried out in only a small number of patients. More research is needed to confirm the use of vitamin K and D in blood sugar management.
When You Probably Don’t Need K2
Pairing vitamin K2 with Vitamin D is optional and may not be required for your vitamin D supplements to be effective.
“Taking vitamin D together with vitamin K2 may help support bone mineral density for some people,” Elena Paravantes, MS, RD, a registered dietitian nutritionist and founder of OliveTomato.com, told Health. “However, the overall findings are mixed, and adding vitamin K2 may not always provide additional benefits.”
Concerns about vitamin K2 mostly arise when people with vitamin K deficiency take vitamin D supplements.
For people who already get enough vitamin K from their diet and are not taking medications that interfere with vitamin K metabolism, additional supplementation may not be necessary.
You can get sufficient vitamin K2Â in fermented foods, including fermented butter or cheese. You can also get it in meats and eggs.
Who Should Talk to a Healthcare Provider First
There is currently no known risk to taking vitamin D and K2 together, but both vitamins should be used with caution in certain people, especially those with other underlying health conditions.
“An unanticipated change in vitamin K intake could change the effectiveness of other medications you are taking (such as antibiotics, cholesterol-lowering drugs, and drugs that affect the absorption of dietary fat) and cause harm,” Emma Laing, PhD, RDN, and director of dietetics at the University of Georgia, told Health.
That said, you may need to see a healthcare provider first before pairing vitamin D and K together if:
You are taking other medications
You have either hypocalcemia (low calcium) or hypercalcemia (high calcium)
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