Do you need K1 if you get K2?

December 7, 2025 •

4 min read

While both are forms of Vitamin K, a critical nutrient, over 90% of the Western diet's total Vitamin K comes from K1. However, this doesn't mean K1 and K2 are interchangeable, as their distinct functions and absorption rates mean a complete approach to vitamin K health is required. The question of whether you need K1 if you get K2 depends entirely on the specific health benefits you are targeting.

Quick Summary

This article explores the distinct roles of Vitamin K1 and K2, outlining how K1 primarily supports blood clotting in the liver while K2 provides extra-hepatic benefits for bone and cardiovascular health. It details the differing absorption, bioavailability, and food sources for each form to help you achieve comprehensive vitamin K status.

Key Points

Distinct Roles: K1 primarily functions in the liver for blood clotting, while K2 targets extra-hepatic tissues like bones and arteries.
Poor Substitutes: Receiving K2 does not negate the body's need for K1, nor can K1 adequately serve K2's functions for bone and heart health.
Different Sources: K1 is sourced from leafy greens, while K2 is found in fermented foods and some animal products, with differing bioavailability.
Longer Half-life: The longer half-life of K2 (especially MK-7) allows it to circulate longer and benefit non-liver tissues more effectively than K1.
Silent Deficiency: It is possible to have sufficient K1 for clotting but be functionally deficient in K2, leading to long-term bone and heart issues.
Both are Essential: Optimal health requires adequate intake of both Vitamin K1 and K2 due to their unique, non-interchangeable functions.

Understanding the Differences Between Vitamin K1 and K2

To answer the question, "Do you need K1 if you get K2?" one must first understand that while they share the same vitamin name, they are not functionally the same within the body. Vitamin K is a group of fat-soluble vitamins, with the two most significant forms being K1 (phylloquinone) and K2 (menaquinones). The primary distinction lies in their chemical structure and, consequently, their distribution and function within the body.

The Role of Vitamin K1: The Liver's Priority

Vitamin K1, predominantly found in green leafy vegetables, is best known for its crucial role in coagulation, or blood clotting. Upon absorption, K1 is preferentially and rapidly taken up by the liver. Here, it serves as a necessary cofactor for the activation of clotting factors II, VII, IX, and X, ensuring the body can form clots and stop bleeding. Without adequate K1, your body's ability to coagulate blood would be severely compromised.

The Functions of Vitamin K2: Extra-Hepatic Benefits

In contrast, Vitamin K2 (specifically the longer-chain menaquinones like MK-7) has a longer half-life in the blood and is distributed more effectively to extra-hepatic tissues, such as bones and blood vessels. Its key functions include:

Bone Health: K2 activates osteocalcin, a protein that promotes the incorporation of calcium into the bone matrix, improving mineralization and bone density. Some studies have linked higher K2 intake to a reduced risk of bone fractures.
Cardiovascular Health: K2 activates Matrix Gla Protein (MGP), which prevents calcium from depositing in soft tissues like arteries and kidneys. This mechanism is crucial for preventing arterial stiffness and calcification, thus supporting cardiovascular health.

The Interplay and Insufficiency

While the body can convert a small amount of K1 into the K2 subtype MK-4, this conversion is not sufficient to meet the body's full extra-hepatic needs. Relying solely on K1 for K2's benefits is ineffective due to K1's limited absorption and preferential delivery to the liver. This creates a situation where an individual could have sufficient K1 for blood clotting but still be functionally deficient in K2, experiencing long-term consequences for bone and heart health.

Comparison Table: Vitamin K1 vs. Vitamin K2


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinones)
Primary Function	Blood clotting	Bone and cardiovascular health
Dietary Sources	Green leafy vegetables (kale, spinach, broccoli), some vegetable oils	Fermented foods (natto, some cheeses), animal products (meat, eggs)
Absorption Rate	Low absorption, estimated at <10% from vegetables	Better absorbed, especially when consumed with fats
Circulation Half-life	Short half-life, a few hours	Long half-life (MK-7 can last days)
Distribution in Body	Prioritized for the liver	Extra-hepatic tissues (bones, arteries)

Is It Possible to Rely on Diet Alone?

Achieving optimal levels of both K1 and K2 through diet alone can be challenging, particularly for K2. While K1 is readily available in many common vegetables, its poor absorption from plant sources makes relying on diet difficult. K2 is less common in the typical Western diet, primarily sourced from fermented foods like natto or certain animal products. Most animal sources from industrial farming have lower K2 levels due to feed, making high-quality pasture-raised options or supplementation a more reliable route.

A Balanced Approach for Optimal Health

Ultimately, a balanced approach is necessary. You need K1 for its essential blood clotting functions, and you need K2 for its distinct benefits related to bone and cardiovascular health. Consuming a variety of foods rich in both, or supplementing with K2 (especially the long-chain MK-7), is the most comprehensive strategy. While K1 is critical for short-term health (stopping bleeds), K2 is vital for long-term protection against silent, progressive conditions like osteoporosis and arterial calcification. This dual-focus ensures the body's vitamin K needs are met across both hepatic and extra-hepatic systems.

Conclusion: The Case for Both K1 and K2

The question, "Do you need K1 if you get K2?" is answered with a clear "yes." The two forms of Vitamin K are not substitutes for one another. K1's primary function is supporting blood clotting in the liver, a role that K2 does not effectively replace. K2, in turn, offers unique and crucial benefits for bone density and arterial health that K1 cannot provide, especially concerning long-term extra-hepatic distribution. To ensure complete and optimal health, focusing on a diverse diet that includes both green leafy vegetables for K1 and fermented foods or quality animal products for K2 is the most prudent path forward. In many cases, a vitamin K2 supplement (ideally MK-7) is a wise addition to guarantee these vital extra-hepatic benefits.

CanPrev: Differences and Benefits of Vitamin K1 vs. K2

CanPrev provides an excellent overview of the specific functions of K1 vs. K2 and their respective benefits, noting K2's crucial role in bone and heart health.

Frequently Asked Questions

The main difference is their primary function and tissue distribution. Vitamin K1 is primarily used by the liver for blood clotting, whereas Vitamin K2 is distributed to extra-hepatic tissues like bones and arteries to support bone mineralization and prevent arterial calcification.

While a balanced diet can provide both forms, it can be challenging. K1 from leafy greens is poorly absorbed, and K2 is less common in the Western diet, primarily found in specific fermented foods and certain animal products.

Vitamin K2, particularly the menaquinone-7 (MK-7) subtype, is considered more effective for bone health than K1. It has a longer half-life and is better distributed to bone tissue, where it activates proteins essential for calcium incorporation into the bone matrix.

Neither is more important; they are both essential for different biological processes. K1 is critical for immediate needs like blood clotting, while K2 is vital for long-term benefits concerning bone and cardiovascular health. A holistic approach includes both.

Yes, taking K1 and K2 supplements together is generally considered safe and may be beneficial for ensuring complete coverage of your vitamin K needs. As with any supplement, consult a healthcare professional, especially if taking anticoagulant medications.

Good sources of K1 include kale, spinach, broccoli, and other green leafy vegetables. K2 is found in fermented foods like natto, certain cheeses, and animal products like eggs and meat from pasture-fed animals.

The longer half-life of K2 is due to its different chemical structure. The longer side chain of some menaquinones (like MK-7) allows it to circulate in the blood for several days, whereas K1 is rapidly taken up and cleared by the liver within hours.