MK-4 and MK-7 are both forms of vitamin K2, but they don’t behave in quite the same way in the body.
If you’re choosing a K2 supplement, MK-7 is usually the more practical option because it stays in the body much longer and can have an effect at much smaller doses. That doesn’t make MK-4 unimportant, though. It has some interesting research behind it too, especially for bone health, but the doses used in studies are often much higher than what you’ll find in a typical supplement.
So, which one is actually better? Let’s look at the main differences and what the research says about bones, osteoporosis and heart health.
MK-4 vs MK-7: What’s the difference?
Vitamin K2 isn’t just one vitamin. It’s a group of related forms called menaquinones – simply the scientific name for the different forms of vitamin K2. This is where the “MK” comes from. MK-4 and MK-7 are the two forms you’re most likely to come across in supplements.
One of the biggest differences between them is how long they stay in the blood. MK-4 is cleared fairly quickly, while MK-7 remains in circulation for longer. In research directly comparing MK-4 and MK-7, MK-7 built up in the blood with regular use, while MK-4 did not.
There is another interesting difference. Our bodies can convert other forms of vitamin K, including vitamin K1 from food, into MK-4. Our tissues don’t make MK-7 in the same way. MK-7 is produced by bacteria and is particularly abundant in fermented foods such as natto.
MK-4 vs MK-7 at a glance
| MK-4 | MK-7 | |
|---|---|---|
| What is it? | A form of vitamin K2 | A form of vitamin K2 |
| How long it stays in the blood | Relatively short time | Much longer |
| Can our body make it? | Yes. The body can convert other forms of vitamin K into MK-4 | Our tissues don’t convert other forms of vitamin K into MK-7. MK-7 is produced by bacteria. |
| Food sources | Egg yolks, chicken and some dairy products | Natto is the richest source; smaller amounts are found in some other fermented foods |
| In supplements | Can be used on its own or combined with MK-7; amounts vary considerably between products | Very commonly used in K2 supplements because it stays in the body for longer |
That longer-lasting effect is one of the main reasons MK-7 is so commonly used in K2 supplements. But it doesn’t necessarily mean it’s better for every purpose, which is what we’ll look at next.
So, is MK-4 or MK-7 better?
For an everyday K2 supplement, MK-7 probably has the edge.
Why MK-7 is often the easier choice
MK-7 stays in the body for longer, so it works well with once-daily dosing. In a direct comparison of MK-4 and MK-7, MK-7 built up in the blood with regular use, while MK-4 did not.
It also seems to work at fairly small doses. Research looking at different doses of MK-7 found that even lower amounts were enough to improve signs that vitamin K was being used properly in the body.
But that doesn’t make MK-4 a bad choice
MK-4 is still an important form of vitamin K2, and our bodies make it themselves. The main difficulty is that much of the research showing benefits from MK-4 used much higher doses than you’ll find in a typical supplement.
So, for general supplement use, MK-7 is usually the more practical choice. But that doesn’t automatically mean it is better for every purpose, especially when we start looking at bone and heart health.
MK-4 vs MK-7 for bone health and osteoporosis
Vitamin K is important for healthy bones because it activates osteocalcin, a protein that helps calcium become part of the bone structure. This is one reason K2 has attracted so much interest for bone health and osteoporosis.
What does the research say about MK-7?
There is some promising research, particularly in postmenopausal women. In a three-year study of 244 women, taking 180 µg of MK-7 daily appeared to slow some of the bone loss normally seen with age, including in the spine and hip.
But the results haven’t always been consistent. Another three-year study using 375 µg a day found that MK-7 improved the way vitamin K was being used in the body, but it didn’t significantly improve bone density.
So MK-7 may support bone health, but we can’t say that taking it will necessarily increase bone density or prevent fractures.
What about MK-4?
MK-4 has also been studied quite a lot for osteoporosis, particularly in Japan. But there is one very important difference: the doses were often much higher compared with normal supplements.
Many of these studies used 45 mg of MK-4 a day. Remember that:
1 mg = 1,000 µg
So 45 mg is actually 45,000 µg. That’s very different from the 180 µg of MK-7 used in the study above, and it means we can’t assume that a supplement containing a few hundred micrograms of MK-4 will have the same effect.
Older research also reported some very impressive reductions in fractures with MK-4, but those results need to be treated with caution. Several studies in this area were later retracted because of problems with the data, and a more recent review found that while MK-4 may help with bone density in the spine, it’s still not clear whether it actually prevents fractures.
Which is better if you have osteoporosis?
At the moment, there isn’t enough good evidence to say that MK-4 or MK-7 is clearly better for osteoporosis.
High-dose MK-4 has been studied for many years, while MK-7 has some encouraging research at much smaller, more typical supplement doses. But neither form has strong enough evidence to replace proper osteoporosis treatment.
Which form looks better for heart health?
Vitamin K also activates a protein called matrix Gla protein (MGP), which helps stop calcium building up in places where it shouldn’t, including the walls of blood vessels. This is why researchers have been interested in whether vitamin K2 could help protect the heart and arteries.
What does the research say about MK-7?
Most of the human research in this area has looked at MK-7.
In a three-year study looking at artery flexibility, taking 180 µg of MK-7 a day improved some measures of how flexible the arteries were, especially in women whose arteries were stiffer at the start of the study.
But not every study has found a clear benefit. A 2022 study looked at calcium build-up in the aortic valve – the valve that controls blood flow from the heart into the main artery. MK-7 improved signs that vitamin K was being used properly in the body, but it didn’t significantly slow the calcium build-up itself.
More recently, a 2026 study in people with coronary artery disease found that calcium build-up in the arteries supplying the heart progressed more slowly in people taking MK-7. That’s encouraging, but it still doesn’t tell us whether MK-7 can actually prevent heart attacks or heart disease.
And MK-4?
There is much less human research on MK-4 and heart health. So, if this is your main reason for choosing between the two, MK-7 currently has more evidence behind it.
That doesn’t mean it’s proven to protect the heart, though. The research is still developing, and neither form should be seen as a treatment for heart disease.
What dose of MK-4 or MK-7 should you take?
There isn’t an official recommended daily amount specifically for MK-4 or MK-7, so the doses you see on supplements can vary quite a lot.
For MK-7, many studies have used around 90–360 µg a day, and 180 µg is one of the better-studied amounts.
For MK-4, the picture is less straightforward. Some studies have used lower doses, but many of the well-known osteoporosis studies used 45 mg a day, which is the same as 45,000 µg.
So what does that mean in practice?
If you’re choosing an everyday MK-7 supplement, something in the region of 90–180 µg a day is much closer to the amounts commonly used in supplements and research. There’s no good reason to assume that taking more will give you more benefit.
Vitamin K also has a good safety record and there is currently no official upper daily limit for vitamin K. Still, I wouldn’t use very high-dose MK-4, such as the 45 mg used in osteoporosis studies, unless it had been specifically recommended by a healthcare professional.
And if you take warfarin or another medicine that works by blocking vitamin K, check with your doctor before taking either form of K2.
MK-4 vs MK-7: The bottom line
For most people choosing an everyday vitamin K2 supplement, MK-7 is probably the more practical option. It lasts longer in the body and has more human research at the sort of doses commonly found in supplements.
The research on bone and heart health is promising but not clear-cut, so I’d see K2 as something that may support health rather than a proven treatment for osteoporosis or heart disease.
FAQs
Is MK-4 or MK-7 better for teeth?
We don’t really know yet. There isn’t good human research showing that one form is better than the other for teeth.
There is some interest in vitamin K2 and dental health, and one small study found lower K2 levels in people with gum disease, but that doesn’t prove that taking K2 will improve teeth or gums.
Does MK-4 increase testosterone?
There is some interesting research here, but so far it mainly comes from animals. One study found that MK-4 increased testosterone production in rats, but we don’t have good human evidence showing that taking MK-4 raises testosterone in men.
Can I take MK-4 and MK-7 together?
Yes. Some K2 supplements contain both forms.
Some supplements contain both forms, but we don’t have good evidence showing that taking both works better than MK-7 on its own.
Is vitamin K2 safe to take?
For most people, vitamin K2 appears to be well tolerated at the amounts commonly found in supplements. There is currently no official upper daily limit for vitamin K, although that doesn’t mean taking very large doses will give you extra benefit.
The main exception is if you take warfarin or another medicine that works by blocking vitamin K. Vitamin K supplements can affect how these medicines work, so speak to your doctor before taking K2. Even fairly small doses of MK-7 have been shown to affect this type of blood-thinning medicine.
Should you take vitamin K2 with vitamin D?
You can, and the two vitamins are often combined in supplements.
Vitamin D helps your body absorb calcium, while vitamin K activates proteins involved in using calcium in bones and other tissues. Research combining vitamin D and vitamin K suggests there may be some benefit for bone health, but we don’t have enough evidence to say that everyone taking vitamin D also needs K2.
There also isn’t one proven combination or dose that is right for everyone.
Should K2 be taken with food?
Yes, ideally. Vitamin K is fat-soluble, which means it is absorbed along with fat from food.
Taking your K2 supplement with a meal containing some fat – for example yoghurt, eggs, olive oil, nuts or avocado – makes sense and may help with absorption.
