Vitamin D is one of the most important nutrients for your body, due to its impact on bone health, immune function, cell growth, cardiovascular health, and muscle function. It’s estimated that between 20-50% of people worldwide do not meet the criteria for healthy vitamin D levels, depending on which standard you use.
When shopping for a vitamin D supplement, you may notice that many products combine vitamin D with vitamin K. For years it has been assumed that a person’s vitamin K status affects how well vitamin D works in the body. The thought is that vitamin K may help direct vitamin D into bones rather than arteries.
A recent study put this thought to the test. The study was actually a follow-up analysis of a larger trial that gave 200 adults with high blood pressure and low vitamin D either a daily vitamin D supplement (2,800 IU) or a placebo for 8 weeks. Researchers measured three forms of vitamin K (K1, MK-4, MK-7) in participants’ blood using a highly precise lab method.
What they found is that vitamin K status had no meaningful effect on how well vitamin D worked. Whether someone had high or low vitamin K levels didn’t change how vitamin D affected bone markers (like osteocalcin, CTX, P1NP) or cardiovascular markers (blood pressure, cholesterol, glucose). On the flip side, vitamin D markers didn’t affect vitamin K levels either.
This doesn’t necessarily mean vitamin K is useless; it just means this study didn’t find it enhances vitamin D’s effects. This study was only 8 weeks long and performed in a very specific population (adults with hypertension and low vitamin D). But overall it should potentially change our assumption of vitamin K being a necessary addition to vitamin D supplements.
If you’re considering a vitamin D supplement, know that a plain vitamin D product is likely just as effective as a pricier D+K combo for improving your vitamin D status. As always, more research is needed to fully settle the question, but for now, don’t feel like you’re missing out by skipping the vitamin K.
This story was originally published by Men’s Fitness on Aug 24, 2026, where it first appeared in the News section. Add Men’s Fitness as a Preferred Source by clicking here.