Vitamin K1 and Reduced International Normalized Ratio

Research synthesisLow evidenceMixed effect size3 studies · 3 beneficial · 0 neutral · 0 harmful

Across all 3 studies, vitamin K1 consistently shows beneficial effects on reducing International Normalized Ratio (INR), with effect sizes ranging from small to large. The most-studied dose is 200 μg/day, with effects typically observed at 6 months (180 days median duration) in clinical populations such as patients on warfarin or those with chronic liver failure.

Effective dose range: 200 μg/day
Studied populations: Chinese patients with mechanical heart valves on warfarin, patients with unstable anticoagulation under warfarin, patients with chronic liver failure

Caveats: Evidence base is small (only 3 studies) — conclusions should be considered preliminary. Available evidence is overwhelmingly positive — clinical literature in this area is subject to publication bias (null-result studies are less likely to be published or indexed).

Generated Jul 12, 2026

Doses used in studies

mg/day: 2.5 (median 2.5, IQR 2.5–2.5) — 1 study
μg/day: 200 (median 200, IQR 200–200) — 1 study

Time to effect

Median: 6 months · IQR 4.5 months–8.6 months · Range 3 months–11.2 months — Reported in 3 of 3 studies

3 of 3 papers

Randomized, placebo-controlled trial of orally administered vitamin K1 for warfarin-associated coagulopathy in Chinese patients with mechanical heart valves.
- 2021-03-30
- RCT · n = 80
- European journal of clinical pharmacology 77(9)
- - Heng Zhang
  - Mei Li
  - Xue-Lian Ao
  - Yi-Jun Dong
  - Li Dong
- PubMed: 33783553
- DOI: 10.1007/s00228-021-03127-8
2 Insights on
- Reduced International Normalized Ratio
- High evidence
- Clinical
Patients administered vitamin K1 exhibited a quick reduction in INR values relative to patients administered placebo (29 of 40 [72.5%] vs. 0 of 44 [0%] patients exhibiting INR values from 1.5-2.5 on the day following treatment, respectively, p = 0.000).
Effect
Beneficial
Effect size
Large
Significant
Yes
Dose
2.5 mg
Effect of 200μG/day of vitamin K1 on the variability of anticoagulation control in patients on warfarin: a randomized controlled trial.
- 2013-09
- RCT · n = 54
- Thrombosis research 132(3)
- - Habeeb Majeed
  - Marc Rodger
  - Melissa Forgie
  - Marc Carrier
  - Monica Taljaard
  - Dimitrios Scarvelis
  - Carol Gonsalves
  - Rosendo A Rodriguez
  - Philip S Wells
- PubMed: 23953594
- DOI: 10.1016/j.thromres.2013.07.019
4 Insights on
- Reduced International Normalized Ratio
- High evidence
- Clinical
The intervention was associated with a greater reduction in the change scores for the SD of INRs between the pre and post-randomization periods compared with placebo. The mean change score was -0.259±0.307 with the intervention and -0.046±0.345 with placebo (p=0.026).
Effect
Beneficial
Effect size
Small
Significant
Yes
Dose
200 μg/day
Effect of vitamin K1 on survival of patients with chronic liver failure: A retrospective cohort study.
- 2020-03
- Observational · n = 80
- Medicine 99(13)
- - Zhuang Xiong
  - Yangyang Liu
  - Tianying Chang
  - Xiaohao Xu
  - Shaokai Huo
  - Houbo Deng
  - Tiejun Liu
  - Yan Leng
- PubMed: 32221088
- DOI: 10.1097/md.0000000000019619
2 Insights on
- Reduced International Normalized Ratio
- Moderate evidence
- Clinical
Vitamin K1 reduced the international normalized ratio levels [P < 0.01 (95% confidence interval 0.000-0.002)].
Effect
Beneficial
Effect size
Moderate
Significant
Yes

Vitamin K1 and Reduced International Normalized Ratio

Randomized, placebo-controlled trial of orally administered vitamin K1 for warfarin-associated coagulopathy in Chinese patients with mechanical heart valves.

Effect of 200μG/day of vitamin K1 on the variability of anticoagulation control in patients on warfarin: a randomized controlled trial.

Effect of vitamin K1 on survival of patients with chronic liver failure: A retrospective cohort study.