The United Kingdom Expert Group on Vitamins and Minerals (EVM) last assessed vitamins and minerals for safety in 2003 and set a so-called Safe Upper Level (SUL) or Guidance Level for each micronutrient, provided sufficient data were available. This SUL or Guidance Level reflects the safe maximum amount of a micronutrient that will not cause any side effects when taken daily from all sources for a lifetime.
| The maximum safe daily intake for vitamin K is 1,000 µg. The maximum safe daily intake for vitamin K is 13 times the EU recommended daily intake (Nutrient Reference Value, NRV). |
This value applies to adults 19 years of age and older and considers only the intake of vitamin K from dietary supplements in addition to conventional dietary intake. It does not apply to pregnant or lactating women because of a lack of studies.
The naturally occurring vitamins K1 (phylloquinone) and K2 (menaquinone) have virtually no side effects, even in large amounts.
Several human studies showed no adverse effects for vitamin K doses up to 10 mg (10,000 µg) per day, taken for four weeks. This amount is more than 130 times greater than the NRV and 10 times greater than the safe daily limit.
Only vitamin K3 (menadione), which does not occur naturally, can cause significant side effects when taken in high doses. However, this form does not occur in foods and is not used in dietary supplements.
As undesirable effects of a permanently excessive vitamin K intake with food and dietary supplements, allergic skin reactions can occur in rare individual cases.
A sensitive group of people to excessive vitamin K intake are patients taking anticoagulants (anticoagulants) from the group of coumarins (Marcumar, Warfarin).
- A total daily intake of 500 µg of vitamin K from all sources should not be exceeded to avoid reversal of the anticoagulant effect of the drug.
- Sudden fluctuations in blood vitamin K levels in amounts up to 100 µg – caused by a change in dietary habits or consumption of vitamin K-containing supplements – are considered safe with usual vitamin K intake.
- In borderline vitamin K supply status, even 25 µg of vitamin K supplied can lead to interactions with anticoagulants in individual cases.
Patients on anticoagulant therapy do not need to change their diet or follow a low vitamin K diet. Increasing vitamin K intake during anticoagulant therapy may require readjustment of anticoagulant dosage, if necessary.