Vitamins. γ-glutamyl carboxylase cofactor
ATC code: B02BA-K2 (Menaquinone (vitamin K2) – local code)
Brand names – supplements
Quality of Life Vitamin K2 MenaQ7, Thorne Vitamin K, Life Extension Super K, Doctor's Best Vitamin K2
Supplements are not tested in clinical trials and are not registered as medications.
Vitamin K2 (menaquinone, mainly MK-7 and MK-4) is a γ-glutamyl carboxylase cofactor. It activates Gla proteins: osteocalcin (bone mineralisation), matrix Gla protein (inhibitor of vascular calcification), and clotting factors II, VII, IX, X. Unlike vitamin K1 (phylloquinone) with a predominant role in coagulation, K2 has a more pronounced effect on bone and vascular calcium metabolism. The long half-life of MK-7 (72 hours) allows once-daily dosing.
Not recommended
2009 approved the claim “vitamin K contributes to bone health maintenance” for labelling. Evidence on oral K2 in postmenopausal osteoporosis is limited: the 2008 Booth RCT did not show a significant effect on bone mineral density or fractures. Endocrine Society 2019 does not include K2 in osteoporosis treatment standards. Standard therapy: bisphosphonates, denosumab, teriparatide + calcium + vitamin D.
Japanese guidelines for postmenopausal osteoporosis include MK-4 at 45 mg daily, but this is a narrow local practice not supported by international consensus.
Not recommended
— Anti-aging and longevity: Vitamin K2 for slowing ageing or extending lifespan is not mentioned in international guidelines. The marketing position of “longevity hormone” lacks evidence. In healthy people on a varied diet, supplemental K2 has not shown clinical effects on lifespan or age-related disease incidence.
Not recommended
Cochrane 2020 found no evidence for vitamin K (including K2) in primary cardiovascular prevention. The 2021 JAHA RCT in patients with coronary calcification showed some slowing of progression – not reproduced in larger RCTs. , do not include K2 in cardiology recommendations. The marketing position “K2 prevents vascular calcification” outpaces the evidence.
Pregnancy data are insufficient. Vitamin K at physiological doses from dietary sources is safe. Supplemental K2 in pregnancy is not recommended.
Low K2 content in breast milk is physiological. Newborns routinely receive a single dose of vitamin K1 to prevent haemorrhagic disease of the newborn. Maternal K2 supplementation does not affect infant status.
menaquinone (vitamin K2) is evaluated for the following indications with varying evidence strength: Postmenopausal osteoporosis (evidence tier D), Anti-aging, longevity, and quality-of-life enhancement in healthy adults (evidence tier F), Cardiovascular calcification prevention (evidence tier F). See the full indication matrix with dosing and citations above on this page.
Common side effects of menaquinone (vitamin K2) (≥ 1 in 100): Side effects at standard doses are rare. See the Safety section for uncommon and serious reactions.
FDA category C. Pregnancy data are insufficient. Vitamin K at physiological doses from dietary sources is safe. Supplemental K2 in pregnancy is not recommended.
Low K2 content in breast milk is physiological. Newborns routinely receive a single dose of vitamin K1 to prevent haemorrhagic disease of the newborn. Maternal K2 supplementation does not affect infant status.
menaquinone (vitamin K2) is contraindicated in: Concomitant warfarin therapy – requires anticoagulant dose adjustment; Hypersensitivity to components; Severe hepatic impairment. Full list in the Safety section.
large RCTs did not confirm an effect on cardiovascular morbidity or mortality. Marketing outpaces science.
D3+K2 combinations in supplements are a marketing approach. Evidence that concurrent intake improves vitamin D effects or prevents hypercalcaemia is absent. In patients on adequate D3 doses with a varied diet, additional K2 is not needed.
MK-7 has a longer half-life and is more convenient. Clinical advantages over MK-4 in the general population are not proven. Japanese osteoporosis guidelines actually use MK-4.