Vitamin K: What It Does, Who Needs It, and How It Affects Your Health

When you think about vitamins, you probably think of vitamin C for colds or vitamin D for bones—but vitamin K, a fat-soluble nutrient critical for blood clotting and bone metabolism. Also known as phylloquinone (K1) or menaquinone (K2), it’s the quiet hero keeping your blood from pooling when you cut yourself and your bones from turning brittle over time. Unlike other vitamins, vitamin K doesn’t get talked about much, but it’s doing heavy lifting behind the scenes every single day.

It’s not just about bleeding. If you’re on warfarin (Coumadin), vitamin K is the balancing act you can’t ignore. Too much can make your blood too thick; too little can make it too thin. That’s why people on blood thinners need to keep their vitamin K intake steady—no sudden spinach salads or kale smoothies unless your doctor knows. It’s not a myth; it’s science. A 2023 study in the Journal of Thrombosis and Haemostasis showed that patients who kept their daily vitamin K intake within 50–100 mcg had far fewer dangerous INR spikes than those who swung between low and high amounts. Vitamin K doesn’t just work in isolation—it talks to your meds, your diet, and your liver.

And it’s not just for adults on blood thinners. Babies get vitamin K shots at birth because their guts don’t make it yet, and breast milk doesn’t give enough. Older adults need it too—especially those with osteoporosis. Vitamin K2 helps move calcium into your bones instead of letting it build up in your arteries. That’s why some heart and bone specialists now recommend K2 supplements alongside calcium and vitamin D. It’s not a magic pill, but it’s a missing piece for many.

Here’s what you’ll find in the posts below: how vitamin K interacts with common medications like antibiotics and cholesterol drugs, why some people are at risk for deficiency without even knowing it, and how your diet—yes, even your salad dressing—can make a difference. You’ll also see real-world advice on managing vitamin K with chronic conditions, avoiding dangerous mix-ups with blood thinners, and what to ask your pharmacist when you’re on multiple pills. This isn’t theory. It’s what people actually need to know to stay safe and healthy.