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Vitamin K in dog and cat diets

A short guide to the role of Vitamin K in dog and cat nutrition.

Vitamin K

It belongs to the fat-soluble vitamins. It is responsible for regulating the blood clotting process (it is a cofactor in the synthesis of clotting factors II, VII, IX, and X) and for bone metabolism — it activates proteins that direct calcium to the skeleton instead of to soft tissues [1]. It is additionally produced in the K2 form by gut bacteria, usually in sufficient amounts, which is why in a healthy, balanced diet a deficiency from nutritional causes is practically never seen.

Where it's found: The animal's own gut microbiome (K2), egg yolks (about 20–30 µg/100 g, mainly K2), green vegetables in the dog (spinach, kale, broccoli — K1), organ meats (hearts, kidneys), and uncleaned beef rumen. In a healthy diet it does not require additional supplementation. Importantly, liver — contrary to intuition — is not a rich source of vitamin K (about 3–5 µg/100 g), although it is crucial for other reasons (vitamin A, copper, folates, B12) [1].

Deficiency: In a healthy animal on a varied raw diet it practically does not occur. Clinical deficiency is almost always secondary to disease or poisoning: rodenticide poisoning (rat/mouse poisons block the regeneration of vitamin K — this is the most common cause of acute deficiency, symptoms 2–5 days after ingestion), liver disease, cholestasis, inflammatory bowel disease (IBD), pancreatic disease, or prolonged antibiotic therapy (destroys the flora that produces K2) [2]. The symptoms are a hemorrhagic diathesis — bleeding from the gums and nose, petechiae, blood in the urine or feces, prolonged bleeding from wounds. This is a medical alarm, not a dietary one — it requires an immediate visit to the veterinarian, not a diet correction.

Excess: The natural forms of vitamin K (K1 from plants, K2 from animal tissues and the microbiome) are exceptionally safe — no toxicity from natural food sources has been described and there is no established upper tolerable limit. Even though it is a fat-soluble vitamin, its overdose from natural food does not happen in practice. The threat appears only with extreme overdose of the synthetic form (K3, menadione), which can toxically damage the liver and cause hemolytic anemia — but K3 is not used in a raw diet [3].

Species difference

The dog has a longer digestive tract and a larger pool of fermenting bacteria, so it synthesizes K2 in the intestines fairly efficiently; additionally it can get K1 from green vegetables. The cat as an obligate carnivore has a shorter digestive tract, faster transit, and a smaller pool of bacteria — its intestinal synthesis is less efficient, so it relies more on dietary supply [1]. Cats do not have to eat vegetables for vitamin K — their sources are yolks, organ meats, and the gut contents of whole small animals (quail, day-old mice). In the cat, diseases of the intestines, liver, and bile ducts raise the risk of deficiency faster than in the dog.

What to watch for

The most important practical information: databases (USDA and others) document the K2 content in raw animal products tragically poorly — they focus on K1 in plants, while K2 in muscle, heart, and kidneys is often zero or heavily understated [3]. Therefore, if the calculator shows a dramatic vitamin K deficiency on a diet containing organ meats, yolks, and (in the dog) green vegetables, it is with high probability a database artifact, not a real deficiency. Vitamin K requires the presence of fat in the meal for absorption and works together with vitamin D and calcium in bone metabolism.

Sources

  1. National Research Council (NRC) (2006). Nutrient Requirements of Dogs and Cats, chapter 5. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
  2. Delaney SJ, Dzanis DA (2018). Safety of vitamin K, and its use in pet foods. JAVMA 252(5):537-542. https://doi.org/10.2460/javma.252.5.537
  3. Elder SJ, Haytowitz DB, Howe J, Peterson JW, Booth SL (2006). Vitamin K Contents of Meat, Dairy, and Fast Food in the U.S. Diet. J Agric Food Chem 54(2):463-467. https://doi.org/10.1021/jf052400h
  4. AAFCO (2023). Dog and Cat Food Nutrient Profiles (AAFCO does not set a minimum for vitamin K for dogs — it assumes sufficient endogenous synthesis). https://www.aafco.org