Ask the Pharmacist: 5 reasons not to supplement with vitamin K

Suzy Cohen
UVM Medical Center registered dieticians talk about why we need Vitamin D and how to get more of it.

Vitamin D makers sometimes add vitamin K to their vitamin D formulas, providing both of these nutrients at the same time. This new trend has not been the standard of practice, for good reason.

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In fact, I personally refused to put vitamin K in my own brand of vitamin D because your safety is most important to me. It interacts with antacids, blood thinners, drugs for cancer, seizures, cholesterol and even aspirin. It’s easy to get if you simply eat some coleslaw, a fruit, or a salad. 

When you take a walk in the sunshine to get your vitamin D, do you have to simultaneously eat a salad? No, of course not. It’s the same with supplements, you don’t need both of those nutrients in one soft gel. Is this topic fascinates you, I wrote a longer version and can email it to you if you sign up for my free newsletter at

Now here are other reasons you may just want a plain vitamin D (without the K in it).

Hypercalcemia is more likely

When you take a supplement with both vitamin D and K in it, these both work synergistically to retain more calcium in your body. Hypercalcemia has been linked to atherosclerosis, cardiac arrhythmias, muscle pain or cramps, insomnia as well as agitation. It is what binds with oxalates to form kidney stones.

Vitamin K causes blood to thicken

It is the opposite of a blood thinner. Who wants thicker blood? We’re all trying to thin our blood with fish oils, turmeric, ginger, vitamin E, ginkgo and even prescription medications. You see, vitamin K negates the actions of blood thinners (anticoagulants), which are intended to thin our blood which in turn protects us from stroke and heart attack.

You don’t want a bone formula

Many of you are taking vitamin D for your bones, and the K helps transport the calcium into your bone. In this case you may want the combination formula, but most people do not ingest D supplements for bone health. It’s usually taken to improve immunity, lower blood sugar, ease depression or seasonal affective disorder (SAD), or to restore lost D which occurs from the drug mugging effect of statin cholesterol drugs. 

You just need to raise vitamin D

Those deficient in vitamin D take high doses of the nutrient for a few months to restore levels, but combination supplements will jack up your K (and calcium levels) to a potentially harmful level and confuse the issue. 

It’s easy to eat vitamin K

Supplementing is unnecessary. The recommendations are as follows: Women above 19 years old should consume 90 micrograms (mcg) each day, and men should have 120 mcg. To put this in perspective, one cup of broccoli gives you 220 mcg, one cup of coleslaw provides 160 mcg, kiwifruit provides 63 mcg and sautéed spinach gives you 889 mcg! There are hundreds of foods that offer a substantial amount of vitamin K.

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Suzy Cohen is a registered pharmacist. The information presented here is not intended to treat, cure or diagnose any condition. Visit