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Vitamin K2 MK-7: how to choose a supplement and who should skip it

By the Life in Good Form editors. Updated 2026-10-15.

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What MK-7 is

Vitamin K is a family of compounds. The NIH Office of Dietary Supplements (ODS) explains that phylloquinone (vitamin K1) comes mainly from green leafy vegetables and is the main dietary form. Menaquinones (vitamin K2) are mostly made by bacteria and appear in modest amounts in animal foods and fermented foods. MK-4, MK-7 and MK-9 are the most studied menaquinones.

Natto, a Japanese food made from fermented soybeans, has high amounts of menaquinones. Other fermented foods, such as cheese, contain some too.

ODS notes few data compare the bioavailability of supplement forms. One study found that both phytonadione (synthetic K1) and MK-7 supplements are well absorbed, but MK-7 has a longer half-life.

How much vitamin K you need

The Adequate Intake for adults 19 and older is 120 mcg a day for men and 90 mcg for women, including during pregnancy and breastfeeding.

ODS says most U.S. diets contain an adequate amount of vitamin K. Average intake from food is 122 mcg for women and 138 mcg for men, rising to 164 mcg and 182 mcg when supplements are counted.

Most multivitamins contain vitamin K at less than 75% of the Daily Value. Standalone K products vary more, and ODS notes some provide 4,050 mcg or other very high amounts.

What the research shows for bones and heart

Bones. Vitamin K helps activate osteocalcin, a main protein in bone. Some, but not all, studies link higher vitamin K intake with higher bone density or fewer hip fractures. ODS says it is unclear whether any form of vitamin K supplement reduces osteoporosis risk. The fracture trials in the 2006 meta-analysis ODS describes used MK-4 at 15 or 45 mg a day, mostly in postmenopausal women in Japan, not the 100 mcg MK-7 doses sold in most stores.

Heart. Matrix Gla-protein, which depends on vitamin K, may help prevent calcium buildup in blood vessels. In a Dutch study of 4,807 adults age 55 and older, people with the highest dietary menaquinone intake (above 32.7 mcg a day) had a 57% lower risk of dying from coronary heart disease than those with the lowest intake. That is an observational food study, not proof that supplements prevent heart disease.

The warfarin warning

This is the one safety issue that matters most. ODS says warfarin (Coumadin) and similar anticoagulants work against vitamin K, so people taking them need to keep vitamin K intake consistent. Starting or stopping a K2 supplement can change how warfarin works.

NOW Foods' MK-7 labels tell anyone taking anticoagulant drugs such as warfarin, Coumadin or heparin to consult a physician first.

Otherwise, vitamin K has a strong safety record. The Food and Nutrition Board did not set an upper limit because of its low potential for toxicity, and stated that no adverse effects from vitamin K in food or supplements have been reported in humans or animals.

How to choose an MK-7 supplement

• Dose. 100 mcg is the most common single dose and close to the adult AI. Higher strengths, such as NOW Foods' 300 mcg extra strength, are available, but 100 mcg already sits within the adult AI range.
• Check for vitamin D. Many K2 products are sold combined with D3. If you already take vitamin D, a K2-only product avoids doubling up.
• Form on the label. Look for menaquinone-7 or MK-7 spelled out. Some blends add MK-4 or K1.
• Capsule and base. NOW Foods uses cellulose veg capsules; its 300 mcg version lists MK-7 from chickpea with MCT oil. Many other brands use softgels.
• Daily Value line. Some labels list K2 with no Daily Value established, so compare by mcg.

What to look for when you buy

Questions people ask

What is vitamin K2 MK-7?

MK-7 (menaquinone-7) is a form of vitamin K2 found in fermented foods such as natto. NIH says it is well absorbed and stays in the body longer than vitamin K1.

How much vitamin K2 MK-7 per day?

There is no separate target for K2. The adult Adequate Intake for all vitamin K is 90 mcg for women and 120 mcg for men, and most MK-7 products give about 100 mcg.

Is MK-7 better than MK-4?

They are different. MK-7 lasts longer in the body. MK-4 is the form used, at much higher milligram doses, in the Japanese bone fracture trials.

Can I take vitamin K2 with warfarin?

Only with your doctor's guidance. Vitamin K counteracts warfarin, and people on it need consistent vitamin K intake.

Is vitamin K2 safe?

No upper limit is set, and the Food and Nutrition Board reported no adverse effects from vitamin K in food or supplements. The main risk is the interaction with warfarin and similar blood thinners.

Sources

• Vitamin K: Fact Sheet for Health Professionals (ods.od.nih.gov), NIH Office of Dietary Supplements
• MK-7 Vitamin K2 100 mcg Veg Capsules (www.nowfoods.com/products/supplements/mk-7-vitamin-k2-100-mcg-veg-capsules), NOW Foods
• MK-7 Vitamin K-2, Extra Strength 300 mcg Veg Capsules (www.nowfoods.com/products/supplements/mk-7-vitamin-k-2-extra-strength-300-mcg-veg-capsules), NOW Foods

Sources checked 2026-10-15.