Vitamin K (Phytomenadione)

Description Vitamin K is a fat-soluble vitamin.
Function/ Used for Vitamin K is required for the formation of several of the proteins, called ‘clotting factors’ that regulate blood clotting, which means it helps heal wounds.

Vitamin K is also required for the formation of some proteins which are important for the maintenance of healthy bones and teeth

Intake Recommended intake

EU NRV: 75µg


UK average daily intake

UK dietary intake is unknown.

As a supplement Commonly available as a single supplement.
Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
Found in (dietary sources) Green vegetables such as kale and spinach, potatoes, liver, soya beans and vegetable oils.

Vitamin K is also synthesised by gut bacteria and this contributes significantly towards the daily requirement of the vitamin.

Deficiency None known.
Precautions and contraindications Safe Upper Level: 1000µg/day1
Use in pregnancy and breastfeeding There is no evidence of adverse effects in pregnancy at normal intakes.

New-born infants are routinely given vitamin K injections or supplements.

Interactions e.g. with other medications Those taking anti-coagulants (such as warfarin) should not take supplements containing over 100mg Vitamin K except on the advice of a doctor.

Antibiotics can destroy vitamin K producing bacteria in the gut and may increase requirements for vitamin K.

The weight-loss drug orlistat and cholesterol-reducing drugs may reduce the absorption of vitamin K and other fat-soluble vitamins (A, D, E)2,3

Adverse effects None known.
References 1.     Expert Group on Vitamins and Minerals, 2003.

2.     Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001.

3.     Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.