Vitamin K1 vs K2: a side-by-side comparison

Vitamin K1 vs K2: a side-by-side comparison

Vitamin K1 vs K2

Until recently, when we talked about Vitamin K, we meant K1.

When multivitamins say 'Vitamin K' on the label, they mean K1. It's needed for proper blood clotting. Newborns are given a shot of K1 to prevent excessive bleeding. 

Things have changed in the last 10 years. We know a LOT more about Vitamin K2 and its effect on health. 

Vitamin K1 and K2 are similar, but they're not the same. 

Side-by-side comparison of Vitamin K1 and K2:

Vitamin K1

Vitamin K2


Phylloquinone (single substance)

Menaquinone (a family of similar molecules called MK, from MK-4 to MK-13. MK-4 is the type most often consumed in food.)

What does it do?

Blood clotting - prevents excessive bleeding. (K1 is what prevents a paper cut from becoming dangerous.) 

  • Helps direct calcium to the right places (into bones and teeth and out of soft issues like arteries and kidneys)

  • May help support bone, heart and brain health.

Found in

Green leafy vegetables

Contained in multivitamins?




Yes, best if eaten with some fat

Yes, best if eaten with some fat


Rare, except in newborns.


Daily Value (RDA)

90 micrograms for women

120 micrograms for men

Not yet established, but experts recommend 100 to 200 micrograms of K2 daily.


No known toxicity if taken at recommended levels.

No known toxicity if taken at recommended levels.

Deficiency symptoms
  • Bruises
  • Increased bleeding time
  • Small blood clots under nails
  • Increased bleeding in mucous membranes.
  • Weak bones
  • Increased plaque deposits along gumline
  • Increase in cavities
  • Arterial calcification
Causes of deficiency
  • Lack of green leafy vegetables in diet
  • Anticoagulant medications (Warfarin/Coumadin)
  • Antibiotics
  • Fat malabsorption disorders.

Lack of fermented foods and organ meats in diet.

Circulation in blood
Brief (hours)

Prolonged (days).

Due to Vitamin K2's longer molecule, it is transported by different carriers in the blood than K1 and therefore, to different locations in the body. 

Effect on bone health



Effect on heart health
Minimal Moderate
Present in brain


The MK-4 form of Vitamin K2 is the predominant form found in the brain, but we don't yet know what it does there. 

What happens after consumption?
  • Vitamin K1 travels to liver more effectively than to bones.
  • Liver uses Vitamin K1 to activate proteins needed for blood clotting.
Effect on gene expression

No known influence on gene expression.

MK-4 form of Vitamin K2 shows some influence on gene expression.

Interferes with function of blood thinning medications

Yes. Anti-coagulant medications work by creating an artificial Vitamin K deficiency. 

Yes. Vitamin K2 can also interfere with the blood thinning medications. Talk to your doctor before using Vitamin K2 supplements if you are taking Warfarin or other similar drugs. 

Dietary contribution to Vitamin K activity

Major. Close to 90% of Vitamin K in western diets is from Vitamin K1. 

K2 as MK-4: minor as a direct dietary source of Vitamin K.

K2 as MK-7: minor as a direct dietary source of Vitamin K

As MK-10 to MK-13: minor. 


Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health.
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