Updated: January 25, 2026

What Is Mephyton (Phytonadione)? Uses, Dosage, and What You Need to Know in 2026

Author

Peter Daggett

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What Is Phytonadione Used For?
What Does Phytonadione Look Like?
Dosage: How Much Phytonadione Do You Take?
How to Take Phytonadione Tablets
Is Mephyton Available in 2026?

Mephyton (phytonadione) is a synthetic vitamin K1 used to treat bleeding disorders and reverse warfarin. Here's everything you need to know about uses, dosing, and 2026 availability.

Mephyton is the brand name for phytonadione—a synthetic, prescription-strength form of vitamin K1. While vitamin K occurs naturally in foods like leafy greens, Mephyton is a pharmaceutical-grade dose used to treat conditions where the body cannot maintain normal blood clotting.

Note: The Mephyton brand has been discontinued. Generic phytonadione 5 mg tablets from multiple manufacturers remain available as the equivalent substitute.

What Is Phytonadione Used For?

Phytonadione is FDA-approved for the treatment of adults with coagulation disorders caused by vitamin K deficiency or vitamin K interference. Specifically:

Warfarin (anticoagulant) overdose or supratherapeutic INR: If your blood thinner (warfarin/Jantoven) has made your blood too thin (INR too high), phytonadione reverses the effect to bring clotting back toward normal.

Hypoprothrombinemia from antibiotics: Prolonged antibiotic use can deplete gut bacteria that produce vitamin K, causing deficiency. Phytonadione replaces it.

Malabsorption conditions: Conditions like celiac disease, Crohn's disease, obstructive jaundice, or biliary fistulas can impair absorption of fat-soluble vitamins including vitamin K.

Other drug-induced vitamin K depletion: Some medications other than warfarin can interfere with vitamin K metabolism.

Neonatal vitamin K deficiency bleeding: Injectable phytonadione is given to newborns at birth to prevent vitamin K deficiency bleeding (VKDB), a potentially life-threatening condition.

What Does Phytonadione Look Like?

Phytonadione 5 mg oral tablets are yellow, round, scored tablets. In its raw form, phytonadione is a clear to yellow-amber, viscous liquid. The oral tablets are reformulated as a solid dosage form for convenient swallowing.

Dosage: How Much Phytonadione Do You Take?

The dose of phytonadione depends entirely on your specific condition and your INR/prothrombin time response. Your doctor will determine the right dose for you. General dosing guidelines:

Anticoagulant-induced hypoprothrombinemia: Initial dose of 2.5 mg to 10 mg orally (up to 25 mg). Your INR should be checked after 6-8 hours. The dose may be repeated if the INR remains elevated after 12-48 hours.

Other causes of hypoprothrombinemia: 2.5 mg to 25 mg or more (rarely up to 50 mg) depending on severity.

Onset of action for oral tablets: effects on prothrombin time generally begin within 6-10 hours of taking the dose.

How to Take Phytonadione Tablets

Take exactly as prescribed—do not adjust the dose without your doctor's guidance

Can be taken with or without food

Store at room temperature (68-77°F); protect from light by keeping in the original container

If you have obstructive jaundice, bile salts must be given alongside phytonadione for it to be absorbed properly

Your doctor will monitor your response with regular blood tests (INR or prothrombin time)

Is Mephyton Available in 2026?

The Mephyton brand is discontinued. However, generic phytonadione 5 mg tablets are still manufactured by multiple companies including Major Pharmaceuticals, Zydus, and Amneal. There is no active FDA shortage listing as of 2026, but not every pharmacy stocks the generic routinely.

If you're having trouble finding it, medfinder can contact pharmacies near you to check for availability on your behalf. Enter your medication name and location, and get results by text.

Want to understand the science? Read our guide on how phytonadione works for a deeper look at its mechanism.

Frequently Asked Questions

Mephyton (phytonadione) is used to treat vitamin K deficiency and related bleeding or blood clotting problems. Most commonly, it's used to reverse the effects of warfarin when the INR has become too high, or to treat deficiency from malabsorption conditions, antibiotic use, or other drug interactions.

Oral phytonadione tablets typically begin exerting their effect on prothrombin time within 6-10 hours. An immediate coagulant effect should not be expected—the medication works by helping the liver produce new clotting factors, which takes time. IV phytonadione works somewhat faster, with measurable improvement in prothrombin time within 1-2 hours.

There is no clinical difference. Mephyton was the original brand name for phytonadione 5 mg oral tablets, manufactured first by Merck and later Bausch Health. The brand was discontinued. Generic phytonadione from manufacturers like Major, Zydus, and Amneal contains the same active ingredient at the same dose and meets the same FDA standards.

Phytonadione is specifically vitamin K1 (also called phylloquinone). It is a prescription-strength synthetic form of vitamin K1. There are also over-the-counter vitamin K supplements, but they are much lower-dose and are not therapeutic equivalents for treating coagulation disorders.

The retail cash price for generic phytonadione 5 mg (30 tablets) is approximately $67-$80 without insurance. With GoodRx or SingleCare coupons, the price drops to approximately $21-$27. Most insurance plans cover it as a Tier 1 or Tier 2 generic with a low or no copay.

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