Vitamin K is a fat-soluble vitamin with two main natural forms: K1 (phylloquinone) from leafy greens, and K2 (menaquinones, often called MK-4 and MK-7) from fermented foods and animal foods, and made by some gut bacteria.

Vitamin K works as a helper to an enzyme called gamma-glutamyl carboxylase. This enzyme adds a carboxyl group to certain proteins so they can bind calcium. In the liver, this activates clotting factors, which is why vitamin K is needed for normal blood clotting. In other tissues, it activates osteocalcin, a protein that binds calcium in bone, and matrix Gla protein, found in blood vessel walls. Absorption needs dietary fat. MK-7 stays in the blood longer than K1 or MK-4, so smaller daily amounts may keep levels steady (NIH Office of Dietary Supplements).

• Helps maintain normal blood clotting
• Helps maintain healthy bones as part of a balanced diet
• May help support the body's use of calcium
• Helps relieve vitamin K deficiency when dietary intake is inadequate
• May help support bone health when combined with vitamin D and calcium

What is the difference between vitamin K1 and K2?

K1 comes mostly from leafy greens and is used mainly by the liver for clotting. K2 comes from fermented foods and animal foods, lasts longer in the blood and is more involved with bone and tissue use of calcium.

Should I take vitamin K with vitamin D?

They are often combined because both are involved in how the body handles calcium. Take them with a meal that contains some fat to help absorption.

Vitamin K affects blood clotting and can interfere with warfarin, so do not use it if you take warfarin or other blood thinners unless directed by your doctor. Speak to your health professional if you have a clotting disorder, are pregnant or breastfeeding.

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