Some people online say they take vitamin D with vitamin K2 because they believe the pairing improves how the body uses vitamin D. Early research suggests that the two nutrients may work together to support bone health, but more studies are needed to confirm the benefits.
We asked Natalie So, PharmD, clinical supervisor of pharmacy services at MedStar Georgetown University Hospital, if there are true benefits for taking vitamin D and K2 together.
*This interview has been edited and condensed for clarity.
Q: We’ve seen online discussions about how vitamin K2 helps direct vitamin D to the right places in the body, and it’s pointless to take vitamin D on its own. Is that true? Do we need to take vitamin D and K2 together?
So: The short answer is no, you don’t have to take vitamin D and K2 together. Taking them together is optional and not a requirement.
Currently, in the U.S., there are no guidelines or major health organizations that recommend or require taking vitamin D and K2 together.
Some people think you should take them together because they may complement each other. Vitamin D helps our bodies absorb calcium, maintains bone health and bone strength, and supports muscle function. When vitamin D levels rise, our body will absorb more calcium, either from food or from supplements.
Vitamin K2 helps activate proteins that move calcium into our bones and makes bones stronger. It also helps prevent calcium from depositing in other places in your body, like arteries instead of bones.
The theory is that taking vitamin D without K2 could increase the risk of calcium going to the wrong places. But this has not been proven in any clinical trials. While it might make sense biologically, there is no data to support that.
Q: Is it safe to take them both together?
So: Generally, it is considered safe. You should just consider other foods or medications you’re taking as well.
K2 can interact with some medications, including blood thinners like warfarin. Vitamin D supplementation alone has been demonstrated to be safe.
Vitamin D and Vitamin K2 are both fat-soluble. People who are generally healthy and have normal kidney function can excrete excess water-soluble vitamins in their urine. But excess fat-soluble vitamins are stored in fat tissues and the liver.
Although vitamin D toxicity is rare, the main concern of having too much vitamin D is hypercalcemia, or excess calcium in the blood. Hypercalcemia can lead to nausea and vomiting, weakness, and frequent urination.
Vitamin K toxicity is rare as well, and it depends on the type or form of vitamin K involved. As always, it is best to speak with a healthcare professional before taking any vitamin supplements to ensure they are safe and to determine the appropriate amount to take.
Brown is a nutrition writer who received her Didactic Program in Dietetics certification from the University of Tennessee at Knoxville. Previously, she worked as a nutrition educator and culinary instructor in New York City.
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