What drug is known as vitamin K? A guide to phytonadione and its role in diet

October 23, 2025 •

4 min read

Did you know that newborns are routinely given a vitamin K shot to prevent a severe bleeding disorder? This is a medical application of phytonadione, the synthetic drug form commonly associated with the vitamin K family, which plays a critical role in blood clotting and bone health.

Quick Summary

Phytonadione is the drug form of vitamin K1, medically used to treat and prevent bleeding issues related to vitamin K deficiency and reverse anticoagulant effects. Menadione (vitamin K3) is a different synthetic form and is unsafe for human consumption. Natural vitamin K comes from dietary sources like leafy greens and fermented foods.

Key Points

Phytonadione is the drug form of vitamin K: Specifically, it is the synthetic version of Vitamin K1 (phylloquinone), used for medical treatments.
Vitamin K has three forms: K1 (phylloquinone) from plants, K2 (menaquinone) from bacteria and animal products, and K3 (menadione), a synthetic and toxic form not for human use.
Drug vs. dietary vitamin K: Phytonadione is a high-dose, targeted medical treatment, while dietary vitamin K is for maintaining normal health and is absorbed with fats.
Used to reverse anticoagulants: Phytonadione is commonly administered to counteract the effects of blood thinners like warfarin in emergency situations or to manage dose changes.
Crucial for newborns: A phytonadione injection is routinely given to newborns to prevent Vitamin K Deficiency Bleeding (VKDB), a potentially life-threatening condition.
Essential for bone and heart health: Beyond clotting, vitamin K, particularly K2, plays an important role in bone mineralization and potentially in preventing arterial calcification.

The Different Forms of Vitamin K

Vitamin K is a family of fat-soluble vitamins, with two main natural forms and one synthetic form. Understanding these distinctions is crucial, especially when considering the medical and dietary implications of this vital nutrient.

Vitamin K1 (Phylloquinone)

Found predominantly in plants, this form is a key component of the human diet. Excellent sources include green leafy vegetables like spinach, kale, and broccoli, as well as some vegetable oils. Phytonadione is the official drug name for a synthetic version of Vitamin K1. It's used therapeutically to treat conditions involving vitamin K deficiency and as an antidote for blood thinners.

Vitamin K2 (Menaquinone)

This form is produced by bacteria, both in the human gut and during fermentation processes. Food sources include fermented products like natto, certain cheeses, and animal products like eggs and meat. Vitamin K2 is particularly noted for its potential benefits to bone and cardiovascular health, as it is believed to help direct calcium to bones and prevent its buildup in arteries.

Vitamin K3 (Menadione)

Menadione is a synthetic form of vitamin K and is considered toxic for human consumption. High doses can lead to liver damage and hemolytic anemia. While it may have historical uses or applications in animal feed, it is not prescribed or recommended for humans due to safety concerns.

Phytonadione: The Drug Known as Vitamin K

When people refer to the drug form of vitamin K, they are almost always talking about phytonadione. As a prescription medication, phytonadione is administered to address specific medical conditions. Brand names include Mephyton and Aqua-Mephyton.

Medical Uses of Phytonadione

Reversing anticoagulant effects: One of the most common applications is counteracting the effects of oral anticoagulants like warfarin. Since warfarin works by blocking vitamin K, providing a supplemental dose of phytonadione can help the body produce clotting factors more quickly, preventing excessive bleeding.
Treating vitamin K deficiency: Phytonadione is used to treat hypoprothrombinemia, a condition where the blood doesn't clot properly due to low levels of vitamin K-dependent clotting factors.
Newborn prophylaxis: All newborns in the U.S. receive a vitamin K injection at birth to prevent a dangerous bleeding disorder called Vitamin K Deficiency Bleeding (VKDB). This is because infants are born with low vitamin K stores and have sterile intestines, so they cannot yet produce their own.

Dietary Vitamin K vs. Phytonadione: A Comparison

It is important to understand the key differences between acquiring vitamin K through diet and receiving phytonadione as a medication. While both provide the same active compound, their applications, absorption, and dosages vary significantly.


Feature	Dietary Vitamin K (K1 & K2)	Phytonadione (Drug)
Source	Plant foods (K1), fermented foods, eggs, meat (K2)	Prescription medication
Administration	Oral, absorbed with dietary fat	Oral tablets, subcutaneous, intramuscular, or intravenous injection
Primary Purpose	Normal nutritional intake for healthy bodily functions	Targeted medical treatment for deficiency or anticoagulant reversal
Dosage	Varies by food intake, typically measured in micrograms (mcg)	Higher, medically prescribed doses (e.g., milligrams)
Absorption	Enhanced by consuming with fats	Often administered via injection for rapid or guaranteed absorption
Potential Interaction	Needs consistent intake while on warfarin	Directly reverses warfarin's effects

Key Considerations for Nutrition and Health

For those on specific medications or with certain health conditions, understanding the relationship between diet, nutrition, and vitamin K is paramount.

Managing Warfarin and Vitamin K Intake

Patients taking warfarin must maintain a consistent daily intake of vitamin K. The anticoagulant effect of warfarin is directly dependent on the amount of vitamin K consumed. Drastic fluctuations in dietary vitamin K can make the medication more or less effective, increasing the risk of either dangerous blood clots or excessive bleeding. A healthcare provider or registered dietitian can help manage dietary intake to ensure stability.

Medications and Malabsorption Issues

Certain medications can interfere with the body's absorption of fat-soluble vitamins, including vitamin K. These can include bile acid sequestrants (like cholestyramine) and weight-loss drugs (like orlistat). Similarly, medical conditions such as celiac disease, ulcerative colitis, cystic fibrosis, and other malabsorption disorders can lead to vitamin K deficiency. In these cases, phytonadione or other supplements might be necessary.

The Importance of a Balanced Diet

For healthy individuals, consuming a balanced diet rich in vitamin K is the best way to maintain adequate levels. This includes a variety of leafy greens, cruciferous vegetables like Brussels sprouts and broccoli, and smaller amounts from sources like eggs and cheese.

Conclusion

While vitamin K is an essential nutrient found in many foods, the specific drug form used in medicine is phytonadione. Its targeted use addresses serious bleeding disorders and manages the effects of anticoagulant medications like warfarin. The difference between dietary vitamin K, essential for everyday health, and its medical counterpart is significant in terms of dosage and application. Understanding these distinctions is critical for patients, especially those on blood thinners, to ensure a balanced approach to both nutrition and prescribed treatment. For specific medical advice, always consult with a qualified healthcare professional.

For more information

To learn more about Vitamin K Deficiency Bleeding (VKDB) and newborn prophylaxis, consult the Centers for Disease Control and Prevention (CDC) at.

Frequently Asked Questions

Dietary vitamin K is absorbed from food sources like leafy greens (K1) and fermented products (K2) to maintain daily bodily functions. Phytonadione is a prescription medication, typically administered in higher doses via injection or tablet, for specific medical conditions like severe deficiency or to reverse anticoagulant effects.

Menadione is a synthetic form of vitamin K that is known to cause toxicity in humans, leading to adverse reactions such as hemolytic anemia and liver damage. For this reason, it is not used in human medicine or supplements.

Newborns are born with very little vitamin K stored in their bodies because it doesn't cross the placenta well. A single phytonadione shot at birth prevents Vitamin K Deficiency Bleeding (VKDB), a rare but serious condition that can cause bleeding into the brain.

Warfarin works by inhibiting the enzyme that recycles vitamin K, preventing the liver from activating clotting factors. Phytonadione, a form of vitamin K, is given to overwhelm this inhibition, allowing for the rapid synthesis of active clotting factors and reversing the anticoagulant effect.

If you are taking blood-thinning medications like warfarin, it is crucial to discuss any vitamin K supplementation with your doctor. Sudden changes in vitamin K intake, whether from diet or supplements, can interfere with the medication's effectiveness. Maintaining a consistent intake is key.

Good dietary sources of vitamin K1 include leafy green vegetables such as kale, spinach, and Swiss chard, and cruciferous vegetables like broccoli. Vitamin K2 is found in fermented foods like natto, as well as animal products like egg yolks and cheese.

Yes, vitamin K is also important for bone health. It activates proteins like osteocalcin that help with bone mineralization. There is also evidence suggesting that vitamin K, particularly K2, plays a role in cardiovascular health by helping to prevent arterial calcification.