Vitamin K1
Last updated: February 11, 2026
Table of Contents
Quick Summary
Vitamin K1 Essential vitamin for blood clotting and bone health. Dogs synthesize some but supplementation ensures adequate levels.
What It Is
Essential vitamin for blood clotting and bone health. Dogs synthesize some but supplementation ensures adequate levels.
Compare to Similar Ingredients
- vs. vitamin k1: Both are vitamin K forms for blood clotting. Vitamin K1 (phylloquinone) is from plants and primarily for clotting factors, while vitamin K2 (menaquinone) is from animal/fermented foods for bone and heart health.
- vs. menadione sodium bisulfite complex: Vitamin K1 (phylloquinone) is natural from plants and safe, while menadione is synthetic vitamin K3 that's toxic and banned in many countries—K1 is far superior.
Why It's Used in Dog Products
Manufacturers include vitamin k1 in dog food, treats, and supplements for several reasons:
- Blood clotting function
- Bone health support
- Prevents deficiency
- Complete nutrition
Quality Considerations
When evaluating vitamin k1 in dog products, it's important to understand bioavailability, synthetic versus natural forms, and deficiency prevention. This ingredient's quality and appropriateness can vary significantly based on sourcing, processing, and the specific formula it's used in.
Essential vitamin that must be in complete dog foods. Dogs produce some via gut bacteria but dietary supplementation ensures adequacy. Critical for blood clotting. Quality depends on stability and bioavailability.
Scientific Evidence
Function and Purpose
Vitamin K1 (phylloquinone) is a fat-soluble vitamin essential for blood coagulation and bone metabolism. It acts as a cofactor for carboxylation of prothrombin and other clotting factors, enabling their conversion to active coagulant proteins. Vitamin K1 is derived from plant sources (leafy greens, alfalfa) or synthetic sources. Dogs can synthesize vitamin K2 (menaquinone) from colonic bacteria, but K1 dietary intake ensures adequate systemic levels. K1 is particularly important in pet foods containing anticoagulant-rich ingredients or for senior dogs where clotting efficiency may decline.
Bioavailability and Efficacy
Vitamin K1 is absorbed with dietary fats in the small intestine; bioavailability is 20-50% due to competitive absorption with other lipophilic compounds. Absorption requires adequate bile acids and pancreatic lipase. K1 has a short half-life (hours) and is not significantly stored; dietary/bacterial K2 production maintains systemic K status. AAFCO does not establish minimum K requirements for healthy dogs, assuming adequate bacterial synthesis. However, supplementation is beneficial in foods containing high-fat protein sources or for dogs with compromised intestinal health affecting bacterial K2 production.
Evidence Rating
Moderate Evidence: Vitamin K is essential for coagulation; however, AAFCO does not mandate supplementation in complete foods, implying adequate endogenous synthesis in healthy dogs. Supplementation provides a safety margin and is beneficial in specific formulation contexts (high-fat, therapeutic, senior formulas).
How to Spot on Labels
Vitamin K1 appears on labels as:
- Vitamin K1
- Phylloquinone (chemical name)
- Vitamin K (may specify K1 separately)
- mcg/kg in guaranteed analysis (less common, K not always listed)
Positioning and Quality Indicators
- Good positioning: Listed among vitamin supplements; indicates premium formulation focus on coagulation health
- Quality indicator: Presence of K1 in foods for senior dogs or therapeutic/recovery formulas suggests comprehensive nutrient coverage
- Concern flag: K1 omission from foods is typical and acceptable (due to bacterial synthesis), but presence is a positive indicator in premium formulations
- Appropriate levels: No AAFCO minimum, but supplemental levels typically 0.1-1.0 mg/kg when included
- Look for: K1 supplementation in foods with high omega-3 content or for senior/therapeutic purposes
Essential vitamin properly included in complete formulas. Vitamin K1 is necessary for blood clotting and bone health. Its presence indicates proper vitamin fortification. Quality formulas specify vitamin forms used.
Frequently Asked Questions
What does vitamin K1 do for dogs?
Vitamin K1 (phylloquinone) is essential for blood clotting—it activates clotting factors that stop bleeding. It also plays a role in bone health by helping regulate calcium. While dogs can synthesize some vitamin K from gut bacteria, supplementation ensures adequate levels, especially important if a dog has digestive issues or has been on antibiotics that disrupt gut flora.
Where should vitamin k1 appear on the ingredient list?
Vitamin K1 appears very late on ingredient lists, typically positions 30-45 among the vitamin supplements. This is normal and expected—vitamins are needed in microgram quantities, so low positioning indicates appropriate dosing, not inferior quality. What matters is that it's present at all, since dogs can synthesize vitamin K from gut bacteria but supplementation provides insurance against deficiency.
Is vitamin k1 necessary in dog food?
Yes. Vitamin K1 helps meet AAFCO nutritional requirements in commercial dog food. Without supplementation, processed foods would lack adequate levels of this nutrient. Without vitamin K, dogs cannot properly clot blood—supplementation provides insurance against deficiency.
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