Vitamin K
Vitamin K activates clotting proteins; warfarin works by opposing this step, so vitamin K intake should stay steady.
Full ranking Dose tool Products (2,020)
Key facts
Sources: https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/ · FDA DV 120 mcg (https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels); pre-2016 DV [80] (https://www.federalregister.gov/documents/2016/05/27/2016-11867/food-labeling-revision-of-the-nutrition-and-supplement-facts-labels); no UL set
How it works: Why is vitamin K linked to warfarin?
- Vitamin K comes as K1 (phylloquinone, mainly from green leafy vegetables) and K2 (menaquinones).
- It is the cofactor of gamma-glutamyl carboxylase, which activates a set of vitamin K-dependent proteins.
- The activated clotting factors (II, VII, IX, X) take part in normal blood clotting.
- Bone proteins such as osteocalcin need the same activation step.
Schematic only; positions and scale are not anatomical.
Sources: NIH ODS: VitaminK Fact Sheet for Health Professionals
Daily dose across products (mcg/day)
Label data from official national databases and brand websites, as declared; not lab-verified.
Common forms
| Form | Products | Median | P5–P95 | Elemental fraction |
|---|---|---|---|---|
| Vitamin K1 (phylloquinone) | 973 | 60 mcg | 10 – 300 | — |
| Vitamin K2 MK-7 | 427 | 60 mcg | 8 – 150 | — |
| Vitamin K2 MK-4 | 115 | 100 mcg | 50 – 5,000 | — |
Common questions
What is the Daily Value for Vitamin K?
The US FDA Daily Value for adults and children aged 4 and over is 120 mcg. It is a labelling reference, not a personal recommendation. [source]
How much Vitamin K do products usually contain per day?
As of 2026-11-01, 2,020 products list a comparable daily dose (2,424 dose records; one product can have several). The median is 60 mcg per day, and 90% of records fall between 7.5 and 550 mcg. Figures come from labels and are not lab-tested. [source]
Why is vitamin K linked to warfarin?
Vitamin K activates clotting proteins; warfarin works by opposing this step, so vitamin K intake should stay steady. No UL has been set. People taking warfarin should keep vitamin K intake steady and ask a doctor before changing it. [source]
What are the side effects of Vitamin K?
Vitamin K has not been shown to cause harm, but it interacts with some medications, especially warfarin. (Source: NIH ODS) [source]
What happens if you take too much Vitamin K?
No UL has been set. The main risk is its interaction with warfarin (see below). (Source: NIH ODS) [source]
Is Vitamin K safe during pregnancy and breastfeeding?
The recommended amount in pregnancy and breastfeeding is 75 mcg (teens) and 90 mcg (women), the same as for other women that age. (Source: NIH ODS) [source]
Does Vitamin K interact with medications or other supplements?
If you take warfarin, keep vitamin K from food and supplements about the same every day: a sudden drop can cause dangerous bleeding and a sudden rise can cause clots. Long-term antibiotics, bile acid sequestrants (cholestyramine, colestipol) and orlistat can reduce vitamin K production or absorption. (Source: NIH ODS) [source]
Top ranked
| Rank | Brand | Product | Per day | Score |
|---|---|---|---|---|
| 1 | USANA | Vitamin K2 | 180 mcg | 100.0 |
| 2 | Whole Foods Market | Vitamin K2 | 100 mcg | 90.4 |
| 2 | Nature Made | Vitamin K2 100 mcg | 100 mcg | 90.4 |
| 4 | XYMOGEN | K2-45 | 90 mcg | 88.9 |
| 4 | Carlson | Vitamin K2 MK-4 (Menatetrenone) | 5,000 mcg | 88.9 |