How many International Units are in one milligram of vitamin K?

Vitamin K Unit Conversion

There is no standardized International Unit (IU) conversion for vitamin K; vitamin K is measured and dosed exclusively in micrograms (μg) or milligrams (mg), not in IUs. 1

Why Vitamin K Has No IU Measurement

• Unlike vitamins A, D, and E, which have established IU conversions based on biological activity assays, vitamin K has never been assigned an IU system by international standards bodies. 2, 3

• Vitamin K is always prescribed, supplemented, and measured in mass units (micrograms or milligrams) in all clinical guidelines and research literature. 4, 5, 1

Standard Vitamin K Dosing in Mass Units

Daily Recommended Intake

• Adult males: 120 μg/day (0.12 mg/day) 1
• Adult females: 90 μg/day (0.09 mg/day) 1

Clinical Treatment Doses

• Routine supplementation after bariatric surgery with malabsorption: 300 μg daily (0.3 mg) 5, 1
• Treatment of documented deficiency: 10 mg intramuscularly or subcutaneously as loading dose, followed by 1-2 mg weekly 4, 5, 1
• Oral treatment for deficiency: 1-2 mg daily 4, 1

Contrast with Other Fat-Soluble Vitamins

• Vitamin A is measured in IUs (10,000-25,000 IU for deficiency treatment) 5
• Vitamin D is measured in IUs (3,000 IU daily for maintenance, 50,000 IU weekly for deficiency) 5
• Vitamin E is measured in IUs (100-400 IU daily for maintenance, 800-1,200 IU for deficiency) 4, 5
• Vitamin K stands alone as the only fat-soluble vitamin without an IU system 1, 2

Critical Clinical Caveat

• Patients on warfarin or other vitamin K antagonists must never receive vitamin K supplements of any form, as this directly interferes with anticoagulation efficacy and creates serious thromboembolism risk. 6, 1

• The absence of an IU system for vitamin K simplifies dosing and eliminates conversion errors that can occur with other vitamins, making mass-based dosing more straightforward in clinical practice. 1, 2