Overview
What is vitamin K?
What are vitamin K’s main benefits?
What are vitamin K’s main drawbacks?
How does vitamin K work?
Dosage information
Formulations:
- Phylloquinone (vitamin K1)
- Menaquinone-4 and menaquinone-7 (vitamin K2)
- Menadione (vitamin K3) is rarely used in supplements.
Range of dosages studied:
- Phylloquinone (vitamin K1): 0.1–10 mg per day (mg/day), equivalent to 100–10,000 micrograms (μg) per day.
- Menaquinone-4 (vitamin K2): 1–90 mg/day (1,000–90,000 μg/day).
- Menaquinone-7 (vitamin K2): 0.09–2 mg/day (90–2,000 μg/day).
Safety information:
Vitamin K interacts with several drugs, including blood-thinning (anticoagulant) drugs like warfarin and drugs that affect the intestinal absorption of dietary fat, such as colesevelam and orlistat. Vitamin K absorption and metabolism can be impaired in people with hepatobiliary dysfunction. A tolerable upper intake level (UL) for vitamin K has not been set, because there is insufficient data assessing the risk.[1][2] This does not mean that taking an amount higher than the recommended dose is safe, just that current data does not find adverse effects.
Dosage recommendation:
The dosages that have been found to improve markers of bone health are 0.1–5 mg/day (100–5000 μg/day) of phylloquinone (vitamin K1), 15–45 mg/day of menaquinone-4 (vitamin K2), or 100–375 μg/day of menaquinone-7 (vitamin K2).[3][4][5]
The adequate intake (AI) — the daily intake that ensures nutritional adequacy in most people — in micrograms (µg) per day for vitamin K is shown below.[1][2] Note that the AI for vitamin K varies slightly between countries; the data below are for the US.
| Age | Male | Female | Pregnancy | Lactation |
|---|---|---|---|---|
| 0–6 months | 2.0 µg/day | 2.0 µg/day | -- | -- |
| 7–12 months | 2.5 µg/day | 2.5 µg/day | -- | -- |
| 1–3 years | 30 µg/day | 30 µg/day | -- | -- |
| 4–8 years | 55 µg/day | 55 µg/day | -- | -- |
| 9–13 years | 60 µg/day | 60 µg/day | -- | -- |
| 14–18 years | 75 µg/day | 75 µg/day | 75 µg/day | 75 µg/day |
| Older than 18 years | 120 µg/day | 90 µg/day | 90 µg/day | 90 µg/day |
Vitamin K is found in several foods. High amounts per serving are found in spinach, broccoli, kale, Brussels sprouts, collards, soybeans, etc.[6][7][8][9] Consult the FoodData Central database to check the amounts of vitamin K in the foods you eat.
Take with food: Yes. Intestinal absorption of vitamin K appears to be improved in the presence of dietary fat.[10]
Frequently asked questions
What are the signs and symptoms of vitamin K deficiency?
What causes vitamin K deficiency?
Should you supplement with vitamin K?
What are other names for Vitamin K?
Update History
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