Vitamin K2: MK-4 vs MK-7, Benefits and How Much to Take

Vitamin K2 is the form of vitamin K that works mostly outside the liver, in bone and in the walls of blood vessels. On supplement labels it usually appears as MK-7 (menaquinone-7) or MK-4 (menaquinone-4). This guide explains what vitamin K2 is, how MK-4 and MK-7 differ, what K2 is good for, how much to take per day, which foods have it, and whether it acts as a blood thinner.

It is educational, not medical advice.

Key Takeaways

• Vitamin K2 activates proteins that direct calcium, including osteocalcin in bone and matrix Gla protein in blood vessel walls.
• MK-7 and MK-4 are both K2. MK-7 is made by bacteria during fermentation and stays in the blood for days. MK-4 is the form your body makes from vitamin K1 and is used at larger amounts.
• How much: the adequate intake for all vitamin K is 90 mcg a day for women and 120 mcg for men. No upper limit has been set, and no harm has been reported from food or supplements in healthy people.
• Best food source: natto, a fermented soybean dish, with about 850 mcg of MK-7 in 3 ounces. Chicken, eggs and cheese provide smaller amounts of MK-4.
• Not a blood thinner. Vitamin K supports normal clotting, so anyone taking warfarin should talk with their clinician before starting K2.

Vitamin K2 Benefits at a Glance

The main benefits of vitamin K2 come from one job: it switches on proteins that direct calcium, in bone and in the walls of blood vessels. Here is what the research in this guide shows, area by area.

Benefit area	What the research shows	Source
Bone	Switches on osteocalcin, a main protein in bone; 180 mcg of MK-7 a day slowed the usual decline in bone density over 3 years in postmenopausal women	Knapen et al., 2013
Blood vessels	Switches on matrix Gla protein in vessel walls; the same 3-year trial found improved measures of arterial stiffness	Knapen et al., 2015
Vitamin K status	MK-7 at about the European daily reference amount increased activation of both osteocalcin and matrix Gla protein in 42 healthy adults	Theuwissen et al., 2012
Normal blood clotting	Like all vitamin K, supports the clotting proteins made in the liver	NIH ODS: Vitamin K
Working with vitamin D	Vitamin D prompts the body to make these proteins, and K2 switches them on	NIH ODS: Vitamin K

If you take K2 as part of a vitamin D routine, the other cofactors are covered in magnesium and zinc together and boron benefits.

What Is Vitamin K2?

Vitamin K is a group of fat-soluble compounds. Vitamin K1 (phylloquinone) comes mainly from leafy greens and is used largely by the liver to make clotting proteins. Vitamin K2 is a family of forms called menaquinones, named MK-4 through MK-13 by the length of their side chain (NIH ODS: Vitamin K). For a fuller side by side look at the two, see our guide to vitamin K2 vs K1.

Most menaquinones are made by bacteria, including bacteria in the gut and in fermented foods. MK-4 is different: the body makes it from vitamin K1 without the help of bacteria, and it is also found in animal foods (NIH ODS: Vitamin K).

For the chemistry of both forms and the amounts used in studies, see our vitamin K2 reference page.

MK-4 vs MK-7: What Is the Difference?

	MK-7 (menaquinone-7)	MK-4 (menaquinone-4)
Where it comes from	Made by bacteria during fermentation	Made by your body from vitamin K1; also in animal foods
Main food sources	Natto (fermented soybeans)	Chicken, eggs, cheese, beef
Time in the blood	Stays for days; still measurable 48 hours after one dose	Leaves the blood within hours
Typical amounts	Micrograms: 180 mcg a day in a 3-year trial	Larger amounts; up to 45 mg a day in Japan

Sources: NIH ODS: Vitamin K, Schurgers et al., 2007, Sato et al., 2012 and Knapen et al., 2013.

Vitamin K2 MK-7

MK-7 has a long half-life. In a study comparing it with vitamin K1, both were absorbed well and peaked in the blood about 4 hours after intake, but MK-7 stayed in circulation much longer, built up to 7 to 8 times higher levels with daily intake, and activated osteocalcin more completely (Schurgers et al., 2007). In another study, a single 420 mcg dose of MK-7 peaked at 6 hours and was still measurable at 48 hours (Sato et al., 2012). That steady level is why MK-7 is used in small daily amounts, measured in micrograms.

Vitamin K2 MK-4

MK-4 is the form of K2 the body makes for itself, converting vitamin K1 into MK-4 in its own tissues (NIH ODS: Vitamin K). It moves out of the blood within hours, so it is used at larger amounts than MK-7. In Japan and other parts of Asia, MK-4 is used at a much larger amount, 45 mg a day, prescribed by clinicians for bone health (NIH ODS: Vitamin K).

Can you take MK-4 and MK-7 together?

Yes. They are two forms of the same vitamin, and some formulas combine them: MK-7 for a steady level in the blood, and MK-4 as the form the body makes itself. Keep the combined amount within what your product label directs.

What Is Vitamin K2 Good For?

Vitamin K is a cofactor for an enzyme that switches on a group of proteins called Gla proteins. Clotting proteins in the liver are usually fully switched on, but 10 to 40 percent of osteocalcin and matrix Gla protein can stay switched off (Theuwissen et al., 2012). That is where extra K2 comes in.

• Bone. Osteocalcin is one of the main proteins in bone (NIH ODS: Vitamin K). In a 3-year trial of 244 healthy postmenopausal women, 180 mcg of MK-7 a day improved vitamin K status and slowed the usual age-related decline in bone mineral density at the spine and hip compared with placebo (Knapen et al., 2013).
• Blood vessels. Matrix Gla protein works in blood vessel walls and may help keep calcium out of them (NIH ODS: Vitamin K). In 42 healthy adults, MK-7 at amounts around the European daily reference value increased the activation of both osteocalcin and matrix Gla protein (Theuwissen et al., 2012). In studies that tracked diets, people who ate more menaquinones, but not more K1, tended to have less calcium in their arteries (NIH ODS: Vitamin K).
• Normal blood clotting. Like all vitamin K, K2 supports the clotting proteins made in the liver.
• A partner for vitamin D. Vitamin D prompts the body to make osteocalcin and matrix Gla protein, and K2 switches them on. See vitamin D3 and K2: benefits, how much to take and when.

Vitamin K2 Benefits for Women

Several of the longer MK-7 trials have enrolled women after menopause, a time when bone density and artery stiffness both tend to change. In a 3-year trial of 244 healthy postmenopausal women, 180 mcg of MK-7 a day slowed the usual decline in bone mineral density at the spine and hip compared with placebo (Knapen et al., 2013). In the same trial, it improved measures of arterial stiffness (Knapen et al., 2015).

In a 1-year trial of 165 women taking the same amount, a follow-up analysis found that blood pressure at the arm was about 3 percent lower in postmenopausal women whose arteries were stiffer at the start (de Vries et al., 2025). These trials describe postmenopausal women; for vitamin D and K2 taken together, see vitamin D3 and K2.

Vitamin K2 Benefits for Men

Most of the longest vitamin K2 trials enrolled postmenopausal women, but the basic benefit applies to men too. In a trial of 42 healthy men and women aged 18 to 45, MK-7 at amounts around the European daily reference value increased the activation of both osteocalcin, a main protein in bone, and matrix Gla protein, which works in blood vessel walls, with no adverse effect on a lab measure of clotting (Theuwissen et al., 2012). In studies that tracked diets, people who ate more menaquinones, but not more K1, tended to have less calcium in their arteries (NIH ODS: Vitamin K). For men who also take vitamin D, K2 switches on the proteins that vitamin D prompts the body to make.

How Long Does Vitamin K2 Take to Work?

MK-7 reaches the blood within hours: a single 420 mcg dose peaked at 6 hours and was still measurable 48 hours later (Sato et al., 2012). With daily intake it builds up, reaching 7 to 8 times higher levels than vitamin K1 (Schurgers et al., 2007). The bigger changes take longer. The bone and blood vessel findings above were measured after 1 to 3 years of daily use (Knapen et al., 2013; Knapen et al., 2015; de Vries et al., 2025), so K2 works best as a steady, long-term daily habit.

Vitamin K2 Dosage for Adults: How Much Per Day?

	Amount
Adequate intake, all vitamin K (adults)	90 mcg a day for women; 120 mcg for men
Pregnancy and breastfeeding	90 mcg a day
Upper limit	None set, because of vitamin K’s low potential for harm
MK-7 in studies	10 to 360 mcg a day; 180 mcg a day in the 3-year bone trial
MK-4 in studies	Larger amounts, up to 45 mg a day in Japan

Sources: NIH ODS: Vitamin K, Theuwissen et al., 2012 and Knapen et al., 2013. There is no separate official amount for K2; the adequate intake covers K1 and K2 together. Follow your product label.

In trials, MK-7 has usually been taken once a day. Women in a 3-year trial took 180 mcg a day (Knapen et al., 2013), and in an 8-week randomized trial of 199 adults aged 65 and over, 180 mcg a day of MK-7 was reported to have good safety (Tan et al., 2024).

Vitamin K2 Foods

Food	Serving	Vitamin K2 (mcg)
Natto	3 ounces	850 (MK-7)
Chicken breast, rotisserie	3 ounces	13 (MK-4)
Ground beef, broiled	3 ounces	6 (MK-4)
Chicken liver, braised	3 ounces	6 (MK-4)
Cheddar cheese	1.5 ounces	4 (MK-4)
Egg, hard boiled	1 large	4 (MK-4)
Mozzarella cheese	1.5 ounces	2 (MK-4)
Milk, 2%	1 cup	1 (MK-4)

Source: NIH ODS: Vitamin K. Outside of natto, most diets supply K2 in small amounts, which is one reason people choose a supplement. Leafy greens are rich in vitamin K1, not K2.

Vegetarian and vegan sources. Natto, made from fermented soybeans, is the plant-based food with the most K2 in the table above. Cheese and eggs give vegetarians smaller amounts of MK-4.

For the full NIH food table, including natto, cheese and eggs, see our guide to vitamin K2 foods.

Vitamin K2 Supplements: How to Choose One

• The form on the label. Look for MK-7, MK-4 or both, named on the label, so you know which form you are taking.
• The amount in micrograms. The adequate intake for all vitamin K is 90 mcg a day for women and 120 mcg for men, and studies of MK-7 have used 10 to 360 mcg a day.
• Alone or with vitamin D3. Many people take K2 alongside vitamin D3, since vitamin D prompts the body to make the proteins K2 switches on. Our guide to vitamin D3 and K2 covers how much of each to take.
• Third-party tested ingredients. Choose a brand that has its ingredients tested by an outside lab.
• Your medicines. If you take warfarin, talk with your clinician before choosing any K2 product.

For a full label checklist when K2 comes with vitamin D3, see our guide to the best vitamin D3 and K2 supplement.

Is Vitamin K2 a Blood Thinner?

No. Vitamin K does the opposite job of a blood thinner: it helps the liver make the proteins that allow blood to clot normally. In healthy adults taking MK-7 at a range of daily amounts, there was no adverse effect on thrombin generation, a lab measure of clotting (Theuwissen et al., 2012).

The caution is for people on warfarin and similar anticoagulants. They need to keep their vitamin K intake steady, because sudden changes can make the medicine work more or less strongly (NIH ODS: Vitamin K). Researchers have noted that 50 mcg a day or more of MK-7 may affect warfarin in a meaningful way (Schurgers et al., 2007). If you take warfarin, talk with your clinician before starting K2.

Vitamin K2 Side Effects and Who Should Check First

No harm has been reported from vitamin K in food or supplements in healthy people, which is why no upper limit has been set (NIH ODS: Vitamin K). Our guide to vitamin K2 side effects goes deeper. Check with your clinician first if any of these apply:

• Warfarin or a similar anticoagulant: keep vitamin K intake steady and ask before adding K2.
• Long courses of antibiotics: they can reduce the gut bacteria that make vitamin K.
• Bile acid sequestrants or orlistat: these can reduce the absorption of fat-soluble vitamins, including vitamin K.
• Conditions that affect fat absorption, or a history of bariatric surgery, which can lower vitamin K status.

Source: NIH ODS: Vitamin K.

Vitamin K2 MK-7 side effects in trials. In an 8-week randomized trial in 199 older adults, 180 mcg of MK-7 a day was reported to have good safety (Tan et al., 2024). In a small randomized trial in hospital patients, 999 mcg of MK-7 a day for up to 14 days was well tolerated and did not increase adverse events (Visser et al., 2024).

Vitamin K2 and blood pressure. In a 3-year randomized trial of 244 healthy postmenopausal women, 180 mcg of MK-7 a day improved measures of arterial stiffness compared with placebo (Knapen et al., 2015). In a 1-year trial of 165 women taking the same amount, a follow-up analysis found that blood pressure at the arm was about 3 percent lower in postmenopausal women whose arteries were stiffer at the start (de Vries et al., 2025). If you take blood pressure medication, check with your clinician before starting a new supplement.

If you take K2 together with vitamin D3, our vitamin D3 and K2 guide covers who should check with a clinician first.

How to Take Vitamin K2

• With a meal that has some fat, since vitamin K is fat-soluble.
• Every day, at the same time, so your levels stay steady.
• With vitamin D if you take it, since the two work on the same proteins. Magnesium helps the body process vitamin D; see vitamin D and magnesium: can you take them together?

From Synchronicity: our Vitamin D3 + K2 Drops include both forms of K2, MK-4 and MK-7, with vegan vitamin D3 from lichen, one drop a day. Each bottle holds about 180 drops, about 6 months at one drop a day.

Sources

• Knapen MH et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int, 2013. PubMed
• Knapen MH et al. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. A double-blind randomised clinical trial. Thromb Haemost, 2015. PubMed
• Theuwissen E et al. Low-dose menaquinone-7 supplementation improved extra-hepatic vitamin K status, but had no effect on thrombin generation in healthy subjects. Br J Nutr, 2012. DOI
• National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. NIH ODS
• Schurgers LJ et al. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood, 2007. DOI
• Sato T et al. Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women. Nutr J, 2012. DOI
• de Vries F et al. Effects of One-Year Menaquinone-7 Supplementation on Vascular Stiffness and Blood Pressure in Post-Menopausal Women. Nutrients, 2025. PubMed
• Tan J et al. Vitamin K2 in Managing Nocturnal Leg Cramps: A Randomized Clinical Trial. JAMA Intern Med, 2024. PubMed
• Visser MPJ et al. Vitamin K2 Supplementation in Hospitalised COVID-19 Patients: A Randomised Controlled Trial. J Clin Med, 2024. PubMed

Frequently Asked Questions

What is vitamin K2?

A family of vitamin K forms called menaquinones. The two most common in supplements are MK-7, made by bacteria during fermentation, and MK-4, the form the body makes from vitamin K1.

What is vitamin K2 good for?

K2 activates proteins that direct calcium, including osteocalcin in bone and matrix Gla protein in blood vessel walls. In a 3-year trial, 180 mcg of MK-7 a day slowed the age-related decline in bone density in postmenopausal women.

Which is better, MK-4 or MK-7?

They do different jobs well. MK-7 stays in the blood for days, so it works in small daily amounts. MK-4 is the form the body makes itself and is used at larger amounts. Some formulas include both.

How much vitamin K2 should I take per day?

The adequate intake for all vitamin K is 90 mcg for women and 120 mcg for men. Studies of MK-7 have used 10 to 360 mcg a day. Follow your product label.

Is vitamin K2 a blood thinner?

No. Vitamin K supports normal blood clotting. If you take warfarin, keep your vitamin K intake steady and talk with your clinician before starting K2.

What foods have vitamin K2?

Natto is by far the richest source, with about 850 mcg of MK-7 in 3 ounces. Chicken, beef, eggs and cheese provide smaller amounts of MK-4.

Does vitamin K2 have side effects?

No harm has been reported from vitamin K in food or supplements in healthy people, and no upper limit has been set. The main caution is for people taking warfarin.

What is the difference between vitamin K1 and K2?

K1 comes mainly from leafy greens and is used largely by the liver for clotting. K2 comes from fermented and animal foods and does more of its work in bone and blood vessel walls.

How do I choose a vitamin K2 supplement?

Look for the form (MK-7, MK-4 or both) and the amount in micrograms on the label, third-party tested ingredients, and decide whether you want it alone or with vitamin D3.

Does vitamin K2 affect blood pressure?

In a 1-year trial, blood pressure at the arm was about 3 percent lower with 180 mcg of MK-7 a day in postmenopausal women with stiffer arteries. Check with your clinician if you take blood pressure medication.

What are the benefits of vitamin K2 for women?

In a 3-year trial of healthy postmenopausal women, 180 mcg of MK-7 a day slowed the usual decline in bone density and improved measures of arterial stiffness compared with placebo.

Is it safe to take vitamin K2 every day?

For healthy adults, daily use is how K2 was taken in trials, and no upper limit has been set because no harm has been reported from food or supplements. If you take warfarin, talk with your clinician first.

Should you take vitamin K2 with vitamin D3?

Many people do. Vitamin D prompts the body to make osteocalcin and matrix Gla protein, and K2 switches them on, so the two work on the same proteins.

What are the benefits of vitamin K2 for men?

The same as for women: K2 switches on osteocalcin in bone and matrix Gla protein in blood vessel walls. In healthy adults including men, MK-7 increased the activation of both proteins.

How long does vitamin K2 take to work?

MK-7 reaches the blood within hours and builds up with daily use, but the bone and blood vessel changes in trials were measured after 1 to 3 years.

What are the benefits of vitamin K2 as MK-7?

MK-7 stays in the blood for days, so small daily amounts keep levels steady, and it is the form used in the 3-year bone and blood vessel trials.

These statements have not been evaluated by the Food and Drug Administration. This content is for education and is not medical advice. Our products are not intended to diagnose, treat, cure or prevent any disease. Talk with a healthcare provider before starting a new supplement if you are pregnant, breastfeeding or taking medication.