Patients with unstable control have a poorer dietary intake of vitamin K compared to patients with stable control of anticoagulation

Thromb Haemost. 2005 May;93(5):872-5. doi: 10.1160/TH04-12-0773.


Evidence suggests that alterations in the dietary intake of vitamin K can affect anticoagulation response to warfarin. It is possible that a low and erratic intake of dietary vitamin K is at least partly responsible for the variable response to warfarin in patients with unstable control of anticoagulation. Twenty-six patients with unstable and twenty-six with stable control of anticoagulation completed dietary records of all foods and drinks consumed on a daily basis for two consecutive weeks. The mean daily intake of vitamin K in unstable patients was considerably lower than that for stable patients during the study period (29+/-17 microg v . 76+/-40 microg). The logarithm of vitamin K intake was consistently and significantly lower in the unstable patients than the stable patients over the two week period (5.9+/-0.4 microg v. 6.9+/-0.5 microg; p<0.001; 95% CI: 0.7-1.2). Changes in vitamin K intake between weeks 1 and 2 of the study were negatively correlated with changes in International Normalised Ratio (INR) amongst the unstable patients, however this failed to reach significance (r=-0.25; p=0.22). Daily supplementation with oral vitamin K in unstable patients could lead to a more stable anticoagulation response to warfarin.

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Anticoagulants / pharmacology*
  • Atrial Fibrillation / drug therapy*
  • Blood Coagulation
  • Diet*
  • Drug Interactions
  • Female
  • Humans
  • International Normalized Ratio
  • Male
  • Middle Aged
  • Nutritional Status
  • Time Factors
  • Treatment Outcome
  • Venous Thrombosis / drug therapy*
  • Vitamin K / pharmacology*
  • Warfarin / pharmacology


  • Anticoagulants
  • Vitamin K
  • Warfarin