Vitamin K

What is Vitamin K?

Vitamin K is a fat-soluble vitamin that belongs to the essential nutrient class and plays a crucial role in blood clotting and bone health. This vitamin exists in two main forms: vitamin K1 (phylloquinone) found in leafy green vegetables, and vitamin K2 (menaquinone) produced by bacteria in the gut and found in fermented foods. Vitamin K supplements are used to prevent or treat vitamin K deficiency and support proper blood coagulation function.

Uses

Vitamin K deficiency prevention and treatment: Primary use for individuals with inadequate dietary intake or absorption problems that can lead to bleeding disorders.

Newborn hemorrhagic disease prevention: Administered to newborns to prevent vitamin K deficiency bleeding, a potentially serious condition in infants.

Bone health support: May help maintain bone density and reduce fracture risk by supporting proper calcium utilization in bone tissue.

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Blood clotting disorders: Used in certain bleeding disorders where vitamin K deficiency contributes to impaired coagulation function.

Osteoporosis management: Sometimes recommended as adjunct therapy to support bone mineralization and reduce bone loss in postmenopausal women.

How it works

Vitamin K functions as an essential cofactor for the enzyme gamma-glutamyl carboxylase, which activates specific proteins involved in blood clotting and bone metabolism. In blood coagulation, it enables the production of functional clotting factors including prothrombin, factors VII, IX, and X, which are necessary for proper blood clot formation. For bone health, vitamin K activates osteocalcin and other proteins that help bind calcium to the bone matrix, promoting strong bone structure.

Side effects

Common side effects:

• Nausea
• Stomach upset
• Headache
• Dizziness
• Altered taste
• Injection site reactions (if given by injection)
• Skin flushing
• Decreased appetite

Serious side effects:

• Severe allergic reactions with difficulty breathing
• Excessive blood clotting (thrombosis)
• Liver dysfunction with high doses
• Hemolysis (breakdown of red blood cells)
• Severe injection site inflammation or infection

Warnings and precautions

Individuals taking anticoagulant medications like warfarin should use vitamin K supplements only under strict medical supervision, as vitamin K can counteract these medications’ blood-thinning effects. People with liver disease should exercise caution, as the liver processes vitamin K and liver dysfunction can affect vitamin K metabolism and requirements. Patients with a history of blood clots or clotting disorders should consult healthcare providers before supplementation. Pregnant and breastfeeding women should follow medical guidance for appropriate dosing, as vitamin K is generally considered safe but proper amounts are essential. Those with glucose-6-phosphate dehydrogenase (G6PD) deficiency may be at increased risk for hemolysis with synthetic vitamin K forms.

Interactions

Warfarin and other anticoagulants: Vitamin K directly antagonizes warfarin’s blood-thinning effects and can lead to dangerous clot formation if not properly monitored.

Antibiotics: Broad-spectrum antibiotics can reduce gut bacteria that produce vitamin K2, potentially increasing vitamin K requirements during treatment.

Anticonvulsants: Medications like phenytoin and carbamazepine can increase vitamin K metabolism, potentially leading to deficiency.

Cholestyramine and bile acid sequestrants: These medications can impair vitamin K absorption by binding bile acids needed for fat-soluble vitamin absorption.

Orlistat: This weight-loss medication reduces fat absorption and can decrease vitamin K absorption from the digestive tract.

High-dose vitamin A: Large amounts of vitamin A may interfere with vitamin K absorption and function.

Mineral oil: Regular use can impair absorption of fat-soluble vitamins including vitamin K.

Alcohol: Chronic alcohol consumption can interfere with vitamin K metabolism and increase bleeding risk.

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Evidence summary

There is strong evidence supporting vitamin K’s effectiveness for treating vitamin K deficiency and preventing newborn hemorrhagic disease. The evidence for bone health benefits shows moderate evidence, particularly for reducing fracture risk in postmenopausal women, though results from clinical trials have been mixed. For osteoporosis prevention, there is limited evidence suggesting potential benefits, but vitamin K is typically used as adjunct therapy rather than primary treatment. The role in cardiovascular health has insufficient evidence from human clinical trials, despite promising observational studies. For complete safety profile and additional research information, visit supplement.ge.

Dosage

Typical adult dosages range from 90-120 micrograms daily for general supplementation, with women generally requiring 90 mcg and men 120 mcg per day. For treating deficiency, therapeutic doses may range from 150-300 mcg daily under medical supervision. Newborns typically receive 0.5-1 mg as a single injection or oral dose. Higher doses of 45-180 mg daily have been used in research studies for bone health, but such amounts should only be used under medical guidance. Individual dosage requirements should always be determined by a healthcare provider based on specific health conditions and medication interactions.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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