Although vitamin K is one of the 13 essential vitamins for both dogs and humans, it's also one that tends to be less well known and understood among dog parents.

Let's jump into what we need to know to maximize the potential vitamin K holds for your dog's health!

What is vitamin K

Vitamin K is a fat soluble vitamin (one of four along with A, D, & E). Dogs are able to synthesize Vitamin K in the gut. However, there are many forms of Vitamin K and research continues to reveal benefits of varying forms.

Some forms are found frequently in a homemade diet and others aren't. Commercial dog food can often be a poor source of this nutrient.

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Vitamin K for dogs - what it does

Most often, vitamin K is thought of for its role in helping blood clot, or coagulate, properly, to keep us from excessive bleeding with any injury or wound. But vitamin K’s critical benefits go beyond the blood to many other functions that are vitamin K dependent including skin health, the skeletal system, and the cardiovascular system.

Vitamin K's impact beyond the blood

In fact, 17 different vitamin K-dependent proteins have been identified within the bone, heart, and blood vessels that support cardiovascular health, bone strength, and keep our dogs' (and our) bodies working properly.

For example, Osteocalcin, a protein, is synthesized by osteoclasts and is vitamin K-dependent to function. It is found in bone but also organs including muscles, testes, and the brain.

Vitamin K, calcium, and bone strength

Given vitamin K's intimate relationship with bone, suboptimal vitamin K may be a factor in developing bone mineral loss. Human studies indicate that vitamin K plays a role in getting calcium where it should go and making sure it does not go where it ought not to go- such as the kidneys (i.e. kidney stones).

Forms of vitamin K: 2 natural, 1 synthetic (& not recommended)

There are two natural forms of vitamin K: phylloquinones (vitamin K1) in plant sources and menaquinones (vitamin K2) produced by bacterial flora.

In pet foods, Vitamin K3 (menadione) is used. This form is used for price and stability reasons. It is unnatural and much controversy surrounds its use. Human studies have indicated that it is a toxic substance (in higher doses) that may harm antioxidant status and has been banned from human use since 1963. Regardless of whether vitamin K3 is or is not harmful, there is no doubt that the other natural forms are safer and superior.

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Where to find vitamin K in foods

Vitamin K1:

You can find vitamin K1 in a range of plant-based sources from blueberries to leafy greens such as kale, broccoli, spinach, spring greens, and many more.

Vitamin K2:

Vitamin K2 can be broken down even further by the name of “MK” with a number attached to it (ex: MK-7). 

• MK-4 is abundant in animal foods (like meat). It is theorized that this form is best at protecting tissues from calcium deposits and supports proper gene expression (human studies). 

• MK-7, MK-8, MK-9 are abundant in fermented foods and cheese. MK-7 is thought to be particularly good at supporting exercise performance, metabolic health, and reaches the bones optimally. It also supports blood clotting proteins and proper blood clotting.

A diet that contains fish, animal-based protein (including organs), would be rich in Vitamin K2. Fermented foods could support additional forms of Vitamin K2.

Because each form has its own strengths, it would be ideal to include a combination of the following (as tolerated by your dog):

• Fresh meat (Including organs)
• Raw dairy products
• Fish
• Fermented foods
• General gut support including fiber to support synthesis
• Butter oil

Vitamin K2 amounts will be richer in grass fed and finished (mature) animals. You may find this database to be useful as vitamin K2 is not listed in nutrient databases.

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Vitamin K requirements & deficiencies

For dogs, vitamin K deficiencies tend to be rare (outside of ingestion of poison) and are traditionally characterized by blood clotting disturbances. A gut that is disturbed may also mean suboptimal status of vitamin K which could theoretically affect the bones, skin, brain, kidney, skin and much more. 

We don’t have a lot of data on how vitamin K is absorbed and we only have the NRC to go on for requirements. Since it can be synthesized in the gut, vitamin K requirements are not based on how to support optimal intake, but rather on how to provide enough to dogs who are unable to synthesize the nutrients. This can make vitamin K difficult to dose.

It would make sense to start with the NRC requirements when dosing forms of vitamin K. You can find those requirements here. Otherwise, you can just proactively work toward providing natural amounts from food. 

While there isn’t evidence to “prove” the benefits of dietary intake in addition to adequate synthesis in the gut, evidence doesn’t rule out dietary vitamin K for optimum health.

This is especially true for kibble-fed dogs with compromised guts since vitamin K is not required by AAFCO guidelines (and when it is added it is added as the synthetic K3). It is possible that millions of dogs have suboptimal vitamin K status- but not at levels that would manifest as disturbances to blood clotting.

Deficiency - vitamin K/disease connections

Previously, research only focused on vitamin K deficiency symptoms relating to blood clotting. Evidence does support that the different forms of vitamin K are better at reaching tissues unique to each form and benefits go well beyond blood coagulation. How can we be sure our dogs are receiving the various needed forms of vitamin K? Could this play a role in common diseases we see today?

Interactions with other essential vitamins

High amounts of vitamin A and E may increase the need for vitamin K, as can calcium. Recall now that in every guide on the fat solubles (A, D, and K primarily) we noted that each fat soluble affected one another and worked synergistically together. Vitamin K is no different. Optimal intake of all the fat solubles is absolutely critical for overall well-being and these pre-formed fat solubles are often neglected in western diets.

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Personal experience with K2 (especially in dogs with poor dental health)

It's often anecdotally expressed that homemade diets tend to improve dental health. While there are many factors that go into dental health (for more on regular dental care go to the Dental Health Channel here on Dogly), it's possible that a fresh food diet provides a dietary source of vitamin K2 that promotes dental health (think bone health).

Several years ago we had a wonderful Boxer named Tony. Tony had a heart condition, was older, was kibble fed, and was not a candidate for cleaning. His teeth were in terrible shape. My Dad (Dr. Miller), carefully dosed cod liver oil with butterfats. This contained vitamin A, D, and K2. After a month or two, I was absolutely astonished at the results. When I visited I asked my dad, “Where did you take Tony for his dental?”

I don’t claim that vitamin K will always be beneficial from the diet, but I have personally seen tremendous results when various forms are fed to dogs who have a history of suboptimal intake. Vitamin K2 in humans has been studied for its effects on protecting the brain when conditions like Alzheimer’s is present. The study into vitamin K2 stands as a relatively new advancement in nutrition research.

Steps to evaluate vitamin K in your dog's diet

1. Does your commercial pet food contain vitamin K3 (menadione - the synthetic version of K best to avoid, that's been banned from human use since 1963)?
2. Are you providing various forms of vitamin K2? If not, which foods may provide an array of these compounds that you can include?
3. At this juncture, do you feel you are providing optimal amounts of the fat soluble vitamins (A, D, E, & K)?

Vitamin K is essential in the diet of our canine companions since dogs don’t produce vitamin K on their own. Evaluating your pet's vitamin K intake is important to ensure your pet receives the best vitamin K nutrition possible.

Next up in the Basic Nutrition Channel on Dogly

Now that you have a good understanding of vitamin K and the other fat soluble vitamins, let's continue to the next essential vitamin step-by-step guide on the all-important B vitamins.

Or hop over to the Basic Nutrition Channel if you'd like to ask a question in the Community discussion and start any of the other step-by-step guides in Needed Nutrients. If you ever need more personalized nutrition guidance, please reach out!