Vitamin K: What It Does, Where to Find It, and Why It Matters for Your Health

When you cut yourself, vitamin K, a fat-soluble nutrient essential for blood clotting and bone metabolism. Also known as phylloquinone (K1) or menaquinone (K2), it’s not just about stopping bleeding—it’s about keeping your bones strong and your arteries clear. Most people assume they get enough from greens like spinach or kale, but that’s only part of the story. Vitamin K1 from plants helps with clotting, but vitamin K2, made by bacteria and found in fermented foods or animal products, actually directs calcium to your bones instead of letting it build up in your arteries. Without enough K2, you could be at higher risk for both osteoporosis and heart disease—even if your blood tests look normal.

Here’s the catch: vitamin K doesn’t get much attention. Unlike vitamin D or calcium, you won’t see it on every supplement label. Yet, studies show that up to 40% of adults may not get enough K2, especially if they avoid cheese, natto, egg yolks, or grass-fed butter. Even worse, common medications like antibiotics, blood thinners, and cholesterol drugs can interfere with how your body uses vitamin K. If you’ve been on long-term antibiotics or take warfarin, your vitamin K levels could be quietly dropping without you noticing. And if you’re over 50, your body’s ability to absorb and use vitamin K declines naturally—making dietary sources even more critical.

What’s missing from most health advice is the link between vitamin K and other systems. It doesn’t work alone. It teams up with vitamin D to build bone, and with magnesium to keep calcium where it belongs. If you’re taking calcium supplements but still getting bone fractures, you might not be lacking calcium—you might be lacking vitamin K. And if you’re worried about blood clots or bruising easily, low vitamin K could be the silent cause. You won’t find it in most multivitamins unless you look closely. But you can get it naturally: kale, broccoli, and spinach give you K1; natto (fermented soy), liver, and hard cheeses give you K2. A simple switch—like adding a tablespoon of natto to your morning bowl or choosing grass-fed dairy—can make a real difference.

Below, you’ll find real, practical guides that dig into how vitamin K interacts with medications, what foods actually deliver the most, and how to spot signs you’re not getting enough—even if your doctor hasn’t mentioned it. No fluff. Just what you need to know to protect your blood, your bones, and your long-term health.