How much vitamin K should I take every day? A comprehensive nutrition guide

October 14, 2025 •

4 min read

The Adequate Intake (AI) for vitamin K for adult women is 90 micrograms (mcg) per day, while adult men require 120 mcg daily. For anyone seeking to optimize their diet, answering the question, 'How much vitamin K should I take every day?' is essential for supporting critical body functions such as blood clotting and bone health.

Quick Summary

The recommended daily intake of vitamin K varies by age and gender, but a balanced diet rich in leafy greens and fermented foods typically provides sufficient amounts. Essential for blood clotting and bone health, vitamin K comes in two main forms, K1 and K2. Individuals on anticoagulant medication must maintain a consistent intake to avoid drug interactions. Deficiency is rare in healthy adults.

Key Points

Adult Intake: Adult men need 120 mcg of vitamin K daily, while adult women need 90 mcg, based on Adequate Intake (AI) guidelines.
Consistent Intake on Warfarin: For individuals taking blood thinners like warfarin, maintaining a consistent daily intake of vitamin K is more important than avoiding it.
Rich Food Sources: Excellent sources include green leafy vegetables (K1) and fermented foods and some animal products (K2).
Vital Body Functions: Vitamin K is crucial for producing blood-clotting factors and for proper bone mineralization.
Rare Deficiency: A vitamin K deficiency is rare in healthy adults with balanced diets but can occur with malabsorption disorders or long-term antibiotic use.
Low Toxicity Risk: Natural forms of vitamin K (K1 and K2) have no known toxicity risk, unlike the synthetic version (K3).

Understanding the Recommended Intake

Before discussing vitamin K intake, it's important to understand that unlike many other vitamins, there is no Recommended Dietary Allowance (RDA) for vitamin K due to insufficient evidence. Instead, health authorities have established an Adequate Intake (AI), which is the average daily intake level assumed to be adequate for healthy individuals. These values differ based on age, gender, and life stage, making it important to consider individual needs.

Adequate Intake (AI) for Vitamin K by Life Stage

The National Institutes of Health (NIH) provides the following Adequate Intakes for vitamin K:

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

For most healthy adults, a balanced diet is typically sufficient to meet these targets. However, factors like malabsorption or certain medications can affect vitamin K levels, warranting medical supervision. Always consult with a healthcare professional for personalized guidance regarding vitamin K intake.

The Role of Vitamin K in Your Body

Vitamin K is a fat-soluble vitamin critical for two main physiological processes: blood coagulation and bone metabolism. Its name is derived from the German word for coagulation, 'Koagulation'. It serves as a cofactor for enzymes that produce specific proteins essential for these functions.

Blood Coagulation

Vitamin K is essential for the synthesis of several proteins known as clotting factors, including factors II (prothrombin), VII, IX, and X. Without adequate vitamin K, the body cannot produce these factors, leading to impaired blood clotting and an increased risk of severe bleeding. For this reason, a vitamin K shot is routinely given to newborns to prevent a dangerous bleeding disorder called Vitamin K Deficiency Bleeding (VKDB).

Bone Health

Beyond blood clotting, vitamin K plays a vital role in bone health by activating osteocalcin, a protein that regulates calcium in bone tissue. Sufficient vitamin K helps to ensure proper bone mineralization and strength, while low intake is associated with decreased bone density and a higher risk of fractures. Some studies suggest that vitamin K2, in particular, may offer greater benefits for bone density than K1.

K1 vs. K2: The Main Forms of Vitamin K

There are two primary naturally occurring forms of vitamin K, each with different dietary sources and functions in the body.

Vitamin K1 (Phylloquinone): This form is primarily found in plants, particularly green leafy vegetables, and is most abundant in the average diet. It is preferentially used by the liver for blood clotting.
Vitamin K2 (Menaquinone): Produced by bacteria in the intestines and also found in fermented and animal products. K2 has a longer half-life and is more readily used by extrahepatic tissues like bone and blood vessels.

Dietary Sources of Vitamin K

Meeting vitamin K needs is typically achievable through a balanced diet. Since it is fat-soluble, consuming sources of vitamin K along with some fat, like olive oil in a salad, can improve absorption.

Foods rich in Vitamin K1:
- Green leafy vegetables (kale, spinach, collard greens, turnip greens)
- Broccoli
- Brussels sprouts
- Lettuce
- Soybean and canola oils
Foods rich in Vitamin K2:
- Natto (fermented soybeans), the richest source
- Hard and soft cheeses (Gouda, blue cheese)
- Egg yolks
- Chicken
- Sauerkraut

Factors Affecting Vitamin K Absorption

While most people get sufficient vitamin K from their diet, some conditions can interfere with absorption:

Malabsorption Disorders: Conditions like cystic fibrosis, celiac disease, and Crohn's disease can impair fat absorption, which also hinders vitamin K absorption.
Medications: Prolonged antibiotic use can destroy the gut bacteria that produce vitamin K2. Drugs that interfere with fat absorption can also be a factor.
Very Low-Fat Diets: Because it's a fat-soluble vitamin, extremely low-fat diets can compromise vitamin K absorption.

Vitamin K and Anticoagulant Medications

For individuals taking anticoagulants like warfarin (Coumadin), managing vitamin K intake is crucial for safety and medication effectiveness. Warfarin works by blocking the action of vitamin K.

It is important not to suddenly change the amount of vitamin K in your diet. Maintaining a consistent intake, rather than eliminating vitamin K-rich foods, allows a doctor to set an appropriate and stable warfarin dose. Any significant dietary changes, especially involving large quantities of vitamin K-rich foods, should be discussed with a healthcare provider.

Comparison of Vitamin K Recommendations (mcg per day)


Life Stage	NIH Adequate Intake (AI)	EU Adequate Intake (AI)
Infants (7–12 months)	2.5 mcg	10 mcg
Children (1–3 years)	30 mcg	12 mcg
Children (4–8 years)	55 mcg	20 mcg
Men (19+ years)	120 mcg	70 mcg
Women (19+ years)	90 mcg	70 mcg
Pregnant/Lactating	90 mcg (19+), 75 mcg (14-18)	70 mcg

Note: Differences in recommended intakes can occur due to different methodologies and data used by various health organizations. Always consult a healthcare professional for personalized recommendations.

Conclusion: Prioritizing a Varied Diet

For the vast majority of healthy adults, the focus should be on consuming a varied diet rich in both vitamin K1 and K2 sources to meet daily needs. Incorporating leafy greens, vegetables, and some fermented or animal products ensures a sufficient intake to support blood clotting, bone health, and overall well-being. Unless a healthcare provider recommends it for a specific condition, supplementation is generally unnecessary. Always consult a doctor or registered dietitian if you have questions about your nutritional requirements, particularly if you are on anticoagulant therapy or have a malabsorption disorder.

For further information, the NIH Office of Dietary Supplements provides a comprehensive fact sheet on Vitamin K

Frequently Asked Questions

Vitamin K1 (phylloquinone) is found in plant foods like leafy greens and is primarily used by the liver for blood clotting. Vitamin K2 (menaquinone) is produced by gut bacteria and found in fermented and animal products; it has a longer half-life and is more readily used by tissues outside the liver, such as bones.

Yes, most healthy adults can meet their vitamin K needs by eating a varied and balanced diet that includes plenty of green leafy vegetables and other sources. Deficiency is uncommon in the general population.

The best food sources include green leafy vegetables such as kale, spinach, and broccoli for vitamin K1, and fermented foods like natto, certain cheeses, and egg yolks for vitamin K2.

There is no established Tolerable Upper Intake Level (UL) for natural forms of vitamin K (K1 and K2) because they are considered non-toxic, and adverse effects are rare. However, the synthetic form, menadione (K3), is toxic and not used in supplements.

Vitamin K directly counteracts the effects of warfarin. To ensure the medication remains effective, individuals on warfarin must maintain a consistent, steady intake of vitamin K and should not make sudden changes to their diet without medical advice.

Symptoms of a severe vitamin K deficiency, which is very rare in adults, include excessive bleeding, easy bruising, nosebleeds, and blood in the urine or stool. Diagnosis is confirmed by a healthcare provider, typically with a blood test that measures prothrombin time.

Supplementation is usually not necessary for healthy people who consume a balanced diet. It is most often recommended for those with malabsorption disorders or in specific clinical scenarios, always under a doctor's supervision. Newborns receive a vitamin K injection at birth to prevent bleeding.

No, as a fat-soluble vitamin, vitamin K is not lost during the cooking process. In fact, consuming it with some fat can enhance its absorption.

Vitamin K is essential for activating osteocalcin, a protein that regulates calcium within the bone matrix. This process is crucial for proper bone mineralization and helps maintain strong bones and reduces the risk of fractures.