Vitamin K Dosage and Daily Intake Recommendations

How much vitamin K should you take? You might be surprised to learn that experts say there's no easy answer.

Recommendations for oral dosages of vitamin K depend on the condition and can also be controversial. For example, 100-200 µg/day has been suggested as a dose to stabilize clotting times in patients for people taking anticoagulant drugs as a result of some studies. However, other researchers have challenged these results.^(1, 6)

Experts also caution that too much vitamin K could interfere with anticoagulant drug activity. In fact, 1-5 mg of vitamin K is typically given to counteract the effects of too much warfarin — a common anticoagulant drug. People taking anticoagulant drugs should not take vitamin K at any dosage level without talking to their doctor.^(1, 6)

Dosage for Osteoporosis

Even dosages for one of the most common uses for vitamin K - osteoporosis - aren't set in stone (or bone!) Up to 10 mg/day of vitamin K or 45 mg/day of vitamin K2 has been used in clinical trials involving patients with osteoporosis. However, results have been mixed for vitamin K in terms of increasing bone mass density (BMD). Some studies showed no increase in BMD linked to vitamin K, so some experts are reluctant to recommend vitamin K at all.^(1, 3)

Despite this, decades of dietary studies suggest eating foods high in vitamin K may help limit fractures. Clinical results also indicate vitamin K2 does help increase bone density in postmenopausal women with osteoporosis.^(1, 3, 11)

Daily Adequate Intake

There is not enough information for recommended dietary allowances (RDAs) for vitamin K. The daily adequate intake (AI) recommendations are as follows:⁽¹⁾