Buying Vitamin K2: MK-7, Dosage & What to Look For

If you're looking into bone health or taking a higher dose of vitamin D3, you'll sooner or later come across vitamin K2. The market is full of drops, capsules, and combination products — and the labels talk about MK-7, all-trans, µg, and natto fermentation. This guide calmly walks through what actually matters when buying vitamin K2, what forms exist, and how to tell good quality from weak quality. It's about making an informed purchase decision, not about miracle promises.

Why Vitamin K2 — and Who Benefits From It

Vitamin K is a fat-soluble vitamin the body needs for, among other things, blood clotting and bone metabolism. Under EU law, the approved claims are: vitamin K contributes to the maintenance of normal bones and vitamin K contributes to normal blood clotting. These two health claims are officially vetted and may be used as stated — anything sold beyond that as a "miracle cure" deserves a critical eye.

A distinction is made between vitamin K1 (phylloquinone, found mainly in leafy green vegetables) and vitamin K2 (menaquinone, found among other things in fermented foods like Japanese natto). When people talk about a vitamin K supplement, they usually mean K2, because it's distributed a bit differently in the body and stays available for longer. You can find the basics on the vitamin's role in our guide Vitamin K: Blood Clotting, Bones & K2.

K2 is especially relevant for people who are already supplementing vitamin D3. Both vitamins are fat-soluble and are often considered together — the article Vitamin D3 + K2: Why the Combination Matters explains why. Whether it's genuinely useful for you day to day ultimately depends on your individual situation; no blanket case for everyone needing it can be drawn from this.

In principle, your vitamin K needs can be covered through a balanced diet. Vitamin K1 is abundant in leafy greens like kale, spinach, broccoli, and herbs; K2 is produced, among other things, through fermentation and is found in foods like natto, and in smaller amounts in certain cheeses. If you eat a genuinely varied diet, you're often already getting a solid baseline amount this way. A supplement can still make sense if your diet is one-sided, or if you specifically want to pair K2 with vitamin D3 — that decision is an individual one and doesn't replace a conversation with your doctor.

The K2 Forms: MK-4 vs. MK-7 and All-Trans vs. Cis

"Vitamin K2" isn't a single substance but a family of menaquinones that differ in the length of their side chain. Two of these matter most for supplements:

• MK-4: a short side chain that is metabolized quickly in the body and stays measurable in the blood only briefly. In supplements, MK-4 is usually produced synthetically and used in comparatively high doses.
• MK-7: a longer side chain that stays measurable in the blood for much longer, which is why it's considered the more practical form for once-daily intake. MK-7 is often obtained through fermentation.

With MK-7, there's a second, often-overlooked criterion: the molecule's spatial structure. There's an all-trans form and a cis form. The all-trans variant is considered biologically active; the cis portion contributes practically nothing to the desired effect, yet it's still counted as "K2." So a product labeled "180 µg MK-7" doesn't actually tell you much unless you know how much of that is all-trans. This is exactly where quality and marketing part ways.

In practice, this means two products can carry the same µg figure on the label and still differ significantly in the amount that's actually active. A product with a declared all-trans content of over 99 percent delivers close to the full active dose, while a product without that information may well contain less active K2. The spatial form also matters for stability: all-trans MK-7 from controlled production is chemically more robust, which supports shelf life over the product's use-by period. That's why the all-trans declaration is one of the most telling quality markers there is.

What to Look For When Buying Vitamin K2

The following points will help you read labels realistically — regardless of brand or price.

1. Form and All-Trans Content

For daily use, MK-7 is generally the more practical choice. Make sure the manufacturer declares the all-trans content — reputable brands state figures like "> 99% all-trans." If this information is missing entirely, it's unclear how much of the declared K2 is even active.

2. Dosage in Micrograms

Vitamin K2 is dosed in micrograms (µg), not milligrams. Typical products usually fall somewhere between about 100 and 200 µg per daily serving. What matters is a clear, per-serving figure on the label — "per drop" or "per capsule" — so you know exactly what you're taking. More isn't automatically better; a sensibly declared dose tells you more than an especially high number does.

3. An Oil Base for Absorption

Because vitamin K2 is fat-soluble, it's absorbed especially well from an oil-based formula. Oil-based drops (such as MCT or olive oil) and oil-filled capsules are therefore common forms. Plain compressed powder tablets without any fat content are possible in theory, but it makes sense to take them with a meal that contains fat.

4. Origin and Fermentation

High-quality MK-7 often comes from controlled fermentation — classically linked to Japanese natto. Some raw materials are trademark-protected and stand for standardized quality. Information about origin and manufacturing process is a good sign that the supplier actually knows what's in their product.

5. Purity and Lab Testing

Reputable manufacturers have their batches tested for purity and content and communicate this openly. Look for references to independent lab analysis, a short, easy-to-follow ingredient list, and the avoidance of unnecessary additives. For a general look at how to spot these quality markers, using vitamin D as the example, see Vitamin D Supplements: How to Spot Quality — the same logic applies to K2.

6. Combining With Vitamin D3

K2 is very often sold together with vitamin D3, since many people want to supplement both vitamins at the same time. Whether a combination product or two separate products suits you better depends on the dosage you're aiming for: combination products are convenient, while separate products let you control D3 and K2 independently. You'll find more detail in the guides Buying Vitamin D3 + K2: Dosage & Quality and Taking Vitamin D and K2 Together?.

7. Putting the Price in Perspective

The price per daily serving tells you more than the price per pack. Very cheap products sometimes cut corners on all-trans content or lab testing; very expensive products aren't automatically better. Work out the price per µg and compare products with a similar form and declaration.

Buying Checklist

• Form: prefer MK-7 for daily use.
• All-trans content: declared, and ideally above 99%.
• Dosage: clearly declared in µg per drop/capsule.
• Base: oil-based, or taken with a meal that contains fat.
• Origin: information on fermentation/raw material provided.
• Purity: reference to lab testing, short ingredient list.
• Combination: with or without D3 — matched to your own needs.
• Price: compare per daily serving and per µg.

Taking It: Why Fat Matters

Vitamin K2 is fat-soluble, so it's best absorbed together with some fat — for example with a main meal that contains oil, nuts, avocado, or dairy. With oil-based drops, the fat is already part of the product. Having a fixed time in your daily routine helps you remember to take it. If you're combining K2 with D3, you can take both together with the same meal; practical tips on this are available in Vitamin D: Drops or Capsules?.

Important note: If you're taking blood-thinning medications from the coumarin group (such as phenprocoumon/Marcumar or warfarin), vitamin K directly interferes with how they work. In this case, you should always check with your doctor first before supplementing with vitamin K1 or K2, rather than starting or changing anything on your own.

An Honest Take

Vitamin K2 is not a cure-all. The solid, EU-approved claims relate to its contribution to the maintenance of normal bones and to normal blood clotting — no more, no less. Whether a supplement makes sense for you personally depends on your diet, your vitamin D status, and your overall situation. A balanced diet with green vegetables and fermented foods already provides vitamin K; a supplement can add to that foundation, but it doesn't replace it.

When buying, it's worth paying less attention to eye-catching numbers and more to transparency: a declared all-trans content, a clear µg declaration, an oil base, origin, and lab testing. Checking these points helps you make an informed decision — whether you end up with a pure K2 product or a D3+K2 combination. If you have health concerns or pre-existing conditions, talking to your doctor is the right path.

One last thought on expectations: supplements don't work overnight and don't replace a healthy lifestyle. Vitamin K2 is one building block alongside a balanced diet, exercise, and — especially when it comes to bone health — an adequate supply of vitamin D. Knowing your vitamin D status lets you approach K2 more purposefully; you can find the background in our guide Vitamin D: Dosage, Blood Levels & Winter. That way, buying K2 isn't an isolated, one-off decision, but part of a well-thought-out overall routine.

Frequently Asked Questions About Vitamin K2

We've briefly summarized the most important questions about buying, forms, and taking vitamin K2 below.