Does vitamin K (Vit K) cause blood clots?

Does Vitamin K Cause Blood Clots?

Vitamin K itself does not cause blood clots in healthy individuals, but it is essential for normal blood clotting function by enabling the activation of several coagulation factors.

Vitamin K's Role in Coagulation

Vitamin K serves as a critical cofactor in the blood clotting cascade through the following mechanisms:

• Acts as a cofactor in the carboxylation of glutamic acid residues in coagulation factors II, VII, IX, and X, allowing these proteins to bind to phospholipid surfaces and participate in blood coagulation 1
• In its reduced form (vitamin KH2), it enables the conversion of glutamic acid residues to gamma-carboxyglutamic acid (Gla), which is necessary for these proteins to become biologically active 1
• Without adequate vitamin K, nonfunctional clotting factors are synthesized, which can lead to hemorrhage 2

Evidence on Vitamin K Supplementation and Clotting Risk

In Healthy Individuals

• Research demonstrates that vitamin K2 (menaquinone-7) supplementation at recommended doses (90 μg daily for 30 days) does not affect:

  • Prothrombin time (PT)
  • Activated partial thromboplastin time (APTT)
  • Thrombin time (TT)
  • Activities of coagulation factors II, VII, IX, and X 3

• This indicates that vitamin K supplementation does not alter hemostatic balance or enhance blood clotting beyond normal levels in healthy people without anticoagulation treatment 3

In Patients on Vitamin K Antagonists (VKAs)

Vitamin K administration can reverse the effects of vitamin K antagonists (like warfarin) by:

• Stimulating new synthesis of active coagulation factors 1
• Lowering elevated INR values more rapidly than simply withholding the anticoagulant 4

For patients with excessive anticoagulation (high INR):

• Low-dose oral vitamin K (1-2.5mg) can reduce INR from 5.0-9.0 to 2.0-5.0 within 24-48 hours 4
• For INR >10.0, a higher dose of 5mg may be appropriate 4

Clinical Implications

Normal Physiological Function vs. Pathological Clotting

• Vitamin K is required for normal hemostasis, but supplementation does not typically cause pathological thrombosis in healthy individuals
• The American College of Chest Physicians guidelines suggest against routine use of vitamin K supplementation for patients taking VKAs with stable INRs (Grade 2C recommendation) 5

Special Considerations

• For patients with elevated INRs (between 4.5 and 10) without bleeding, guidelines suggest against routine use of vitamin K (Grade 2B recommendation) 5
• When vitamin K is administered to reverse anticoagulation, oral administration is preferred over intravenous due to risk of anaphylactoid reactions with IV administration 4

Conclusion

Vitamin K is essential for normal blood clotting but does not cause pathological blood clots in healthy individuals. It enables the activation of clotting factors within the normal physiological range. The concern about vitamin K "causing clots" is primarily relevant in the context of patients on vitamin K antagonists, where supplementation can reverse the anticoagulant effect.