How much vitamin K do you need a day?

November 16, 2025 •

5 min read

According to the National Institutes of Health, adult men need 120 mcg and adult women need 90 mcg of vitamin K per day. Understanding how much vitamin K do you need a day is vital for maintaining proper blood clotting and bone health.

Quick Summary

Daily vitamin K intake varies by age and gender, playing a crucial role in blood clotting and bone mineralization. Sources include leafy greens, fermented foods, and supplements.

Key Points

Daily Intake Varies: The Adequate Intake (AI) for adult men is 120 mcg per day, while adult women need 90 mcg per day.
Crucial for Blood Clotting: Vitamin K is essential for the liver to produce the proteins needed for blood coagulation, preventing excessive bleeding.
Supports Bone Health: It helps activate proteins like osteocalcin, which is critical for bone mineralization and density.
Two Primary Forms: Vitamin K1 (phylloquinone) is found in plants like leafy greens, while Vitamin K2 (menaquinones) is in fermented foods, some animal products, and made by gut bacteria.
Impacts Blood Thinners: Those on warfarin must maintain a consistent daily intake of vitamin K to avoid dangerous interactions that can affect the medication's efficacy.
Rich Food Sources are Key: A balanced diet rich in leafy greens, vegetable oils, and certain fermented foods or animal products can easily provide the necessary vitamin K.

Understanding the Recommended Intake of Vitamin K

Vitamin K is a fat-soluble vitamin essential for several vital bodily functions, most notably blood clotting and bone metabolism. Unlike some other fat-soluble vitamins, the body breaks down and excretes vitamin K relatively quickly, so a consistent daily intake from diet is important. Official recommendations for vitamin K are provided as an Adequate Intake (AI) by health authorities, as there is insufficient data to establish a Recommended Dietary Allowance (RDA). These AI values are based on the median intake of healthy individuals and are intended to ensure nutritional adequacy.

Daily Adequate Intake (AI) by Age and Gender

The amount of vitamin K required varies significantly depending on age, sex, and life stage. The following AI values are based on recommendations from the NIH Office of Dietary Supplements and WebMD:

Infants (0-6 months): 2.0 micrograms (mcg) per day
Infants (7-12 months): 2.5 mcg per day
Children (1-3 years): 30 mcg per day
Children (4-8 years): 55 mcg per day
Children (9-13 years): 60 mcg per day
Adolescents (14-18 years): 75 mcg per day
Adult Men (19+ years): 120 mcg per day
Adult Women (19+ years): 90 mcg per day
Pregnant or Breastfeeding Women (19+ years): 90 mcg per day

The Role of Vitamin K in Your Body

Vitamin K is more than just a single nutrient; it is a group of compounds that includes Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinones). Each form plays a slightly different role in the body due to differences in absorption and how they are used by tissues.

Blood Clotting: Vitamin K is famously known as the "clotting vitamin." It acts as a crucial co-factor in the liver's production of clotting factors, including prothrombin. Without adequate vitamin K, the blood would be unable to clot, leading to excessive bleeding.
Bone Health: Vitamin K is necessary for activating osteocalcin, a protein that plays a key role in bone mineralization. Research suggests that sufficient vitamin K intake is associated with stronger bones and a lower risk of fractures, particularly in older adults.
Heart Health: Some research suggests that vitamin K helps produce matrix Gla protein (MGP), which inhibits the calcification (or hardening) of arteries, potentially reducing the risk of cardiovascular disease. This effect is particularly associated with Vitamin K2.

Comparison of Vitamin K1 and Vitamin K2

There are important differences between the two main forms of vitamin K, which affect their sources and function in the body. While the AI is based primarily on vitamin K1, a diet rich in both forms is beneficial.


Feature	Vitamin K1 (Phylloquinone)	Vitamin K2 (Menaquinones)
Primary Sources	Plant-based foods, especially leafy green vegetables like kale, spinach, and broccoli, as well as vegetable oils.	Fermented foods like natto, some cheeses, and animal products like meat and eggs. Produced by gut bacteria.
Main Function	Primarily used by the liver to activate proteins involved in blood clotting.	Distributed more to extrahepatic tissues like bone and blood vessels; better absorbed and has a longer half-life. Plays a more significant role in bone and cardiovascular health.
Bioavailability	Poorly absorbed from plant sources; absorption is enhanced when consumed with fat.	Generally better absorbed, especially the longer-chain forms like MK-7, due to often being found in fat-containing foods.
Circulation	Circulates in the blood for only a few hours.	Can remain in circulation for several days, allowing for wider distribution.

Getting Your Daily Dose of Vitamin K

For most healthy adults, it is possible to meet the daily requirements of vitamin K by eating a varied and balanced diet. Deficiencies are rare, except for those with malabsorption disorders or on long-term antibiotics. The following are some excellent food sources:

Vitamin K1-Rich Foods

Kale
Spinach
Collard greens
Turnip greens
Brussels sprouts
Broccoli
Lettuce
Vegetable oils (e.g., canola, soybean)

Vitamin K2-Rich Foods

Natto (fermented soybeans) is the richest source of MK-7
Hard and soft cheeses
Meat (especially chicken and beef liver)
Eggs

Considerations for those on Blood Thinners

It is crucial for individuals taking blood-thinning medications, such as warfarin (Coumadin), to be mindful of their vitamin K intake. Since vitamin K promotes blood clotting, a sudden change in consumption can interfere with the medication's effectiveness, leading to dangerous bleeding (if intake decreases) or blood clots (if intake increases). People on these medications should aim for a consistent daily intake of vitamin K and consult their healthcare provider or a registered dietitian for personalized dietary advice.

Is Vitamin K Supplementation Necessary?

For the average healthy person, getting enough vitamin K from food alone is sufficient, and supplements are not typically needed. However, specific populations may benefit from supplementation. Newborns, for instance, receive a vitamin K injection at birth to prevent a rare but serious bleeding disorder. Those with digestive conditions that impair nutrient absorption, like Crohn's or celiac disease, may also need supplements under a doctor's supervision. It's important to remember that high-dose supplementation is generally not recommended for vitamin K, as excessive amounts can interfere with medication and potentially cause harm. No Upper Intake Level (UL) has been established for naturally occurring vitamin K1 and K2 due to low toxicity risk. However, excessive intake should still be avoided, especially with synthetic forms.

Conclusion

While a severe vitamin K deficiency is uncommon in healthy adults, ensuring you consume enough of this essential nutrient through a balanced diet is important for maintaining healthy blood clotting and strong bones. Daily intake recommendations, such as the 120 mcg for adult men and 90 mcg for adult women, are easily met by incorporating leafy green vegetables and other vitamin K-rich foods into your meals. It is vital for individuals on blood-thinning medications to manage their vitamin K consumption consistently to prevent dangerous interactions. For most, a varied diet is the best way to get the vitamin K you need a day, supporting your body's critical functions from coagulation to bone mineralization.

Note: This information is for educational purposes only. Always consult a healthcare professional for specific medical advice, especially if you are pregnant, breastfeeding, or taking medications.

For more detailed information, consider reading the NIH Office of Dietary Supplements fact sheet on vitamin K.

Frequently Asked Questions

Vitamin K1 is mainly found in leafy green vegetables and is primarily used by the liver for blood clotting. Vitamin K2, found in fermented foods and animal products, is better absorbed, has a longer circulation time, and is more beneficial for bone and cardiovascular health.

For naturally occurring Vitamin K1 and K2 from food or standard supplements, toxicity is very rare because the body uses it quickly. No Upper Intake Level has been established. However, high doses of synthetic vitamin K3 (menadione) can be harmful.

Symptoms of a severe deficiency include easy bruising, excessive bleeding from cuts, nosebleeds, heavy menstrual periods, and blood in the urine or stool. In adults, this is uncommon but can occur with malabsorption issues or due to certain medications.

Excellent sources of Vitamin K1 include kale, spinach, broccoli, and Brussels sprouts. Good sources of Vitamin K2 are natto, hard cheeses, meat, and eggs.

Vitamin K counteracts the effects of warfarin. Patients on this medication must keep their vitamin K intake consistent to ensure the drug works effectively. Sudden changes can lead to either dangerous bleeding or blood clots.

Yes, newborns have low vitamin K stores at birth and are at risk of a serious bleeding disorder. For this reason, a vitamin K injection is routinely administered shortly after birth.

For most healthy people, a balanced diet provides a sufficient amount of vitamin K. Supplements are generally not needed unless there is an underlying health condition causing malabsorption or if recommended by a healthcare provider.

Vitamin K activates proteins, such as osteocalcin, which are essential for binding calcium and promoting proper bone mineralization. Higher vitamin K intake is associated with greater bone density and a lower risk of fractures.