Vitamin K2: who needs it, which form, and how much

What is vitamin K2?

There are two main types of vitamin K. K1 helps your blood clot, and K2 decides where calcium goes. The names are similar, but they do different jobs.

K2 activates two proteins in your body.

• Osteocalcin: Grabs calcium from your blood and attaches it to bone.
• MGP: Pushes calcium away so it doesn't build up in blood vessel walls, cartilage and organs.

In simple terms, it's calcium's "traffic cop." No matter how much calcium you take, if you're short on K2, the calcium can end up in the wrong places instead of your bones.

K2 is found in fermented foods like natto, and in meat and cheese from grass-fed animals. It's hard to get enough from a modern diet, so many people fall short.

Vitamin K2 benefits: where it may help

• Bone health: It helps calcium actually attach to bone. It's widely used in bone-health stacks with calcium, magnesium and vitamin D.
• Arterial calcification: Calcification is when calcium builds up in blood vessel walls and makes them stiff. K2 activates the protein that pushes this calcium away (MGP), which may help slow how fast calcification progresses.
• Gums and jawbone: Some say it may help strengthen the bone that holds your teeth (alveolar bone).
• Blood sugar: Some research suggests osteocalcin helps insulin work better, but this is still a supporting point.

What does the research show?

Bottom line: studies show it slowed how fast calcification increased, but it didn't remove calcification that was already there.

But the limits are clear, too.

• Calcification didn't shrink — it just grew less.
• These studies didn't confirm whether heart disease actually went down.
• The study doses (360–720 mcg) were much higher than typical supplements (100–200 mcg).
• There still aren't enough analyses pooling large studies (meta-analyses).

So don't think of it as "taking it cleans out your arteries." Think of it as "a supporting tool that helps keep calcium from building up in the wrong places."

Who needs it

• □ You've taken vitamin D3 for a long time, especially at high doses
• □ You take a calcium supplement (including new moms taking calcium and D after giving birth)
• □ A checkup found calcification in your blood vessels, breasts, bladder or elsewhere
• □ You're middle-aged or older and worried about calcification
• □ You rarely eat fermented foods like natto or grass-fed meat
• □ You've had kidney stones or gallstones
• □ You've been told your gums or jawbone are weak

MK-7 vs MK-4: which K2 should you choose?

There are different kinds of K2, too. Always check the label for whether it's MK-7 (menaquinone-7) or MK-4 (menaquinone-4).

Vitamin K2 daily dose and when to take it

Bottom line: 100–200 mcg a day as MK-7, once a day.

1. Once a day is enough. MK-7 stays in your body a long time. With MK-4, you'd need to split it into 3 or more doses a day.
2. Take it with a meal. K2 is a fat-soluble vitamin, so it absorbs better with food.
3. Take it with vitamin D3. D3 boosts calcium absorption, and K2 sends that calcium to your bones. They work as a team.

There's no official upper limit yet (a level you shouldn't go over). Hardly any notable side effects have been reported, even at high doses.

How to choose a vitamin K2 product

1. Make sure it's MK-7 — Look for "Vitamin K2 (as menaquinone-7, MK-7)." It may also carry an ingredient brand name like MenaQ7 or K2VITAL.
2. Check the K2 amount — For K2 alone, look for 100 mcg or more. For a D3 combo, be sure to check how many mcg of K2 it has. 45 mcg or less is on the low side.
3. Check whether K1 is mixed in — Some products also include "Phylloquinone" or "K1." You don't need it, and avoid it especially if you take a blood thinner.

K2 as a raw ingredient costs more than 100 times as much as vitamin D. So the K2 amount basically sets the price. Most cheap D3+K2 products contain very little K2.

Vitamin K2 side effects and warfarin cautions

K2 has very few side effects, even at high doses. Rare hypersensitivity reactions like allergies are about all that's known.

The most important group is people taking the blood thinner warfarin.

• K1 helps blood clot, so it clearly weakens warfarin's effect.
• Many say K2 has less effect. But others say it may have some effect, so it's not settled yet.
• So if you take warfarin, don't start K2 on your own either — always talk to your doctor.

Combinations

Works well with: Vitamin D, Calcium, Magnesium

Frequently asked questions

Related concerns