Vitamin K
Vitamin K1 and K2 supplements in capsules, tablets and drops, including MK-7 and combinations with vitamin D3. We explain how K1 and K2 differ, why we prefer all-trans MK-7 and how to take vitamin K with a meal.Read more →
Filters
Availability
Brand
Form
Diet
Goal
Price
Choosing between vitamin K1, K2 and MK-7
K1 and K2: one vitamin, two ways of behaving
Vitamin K is a group of fat-soluble nutrients, so your body takes it up best with some fat in the meal. Vitamin K1 (phylloquinone) comes from green leaves: kale, spring greens, spinach and broccoli. Vitamin K2 (menaquinone) comes from fermented food such as natto and from some cheeses. On a label both simply count as vitamin K, and both carry the same two approved statements: vitamin K contributes to normal blood clotting and to the maintenance of normal bones.
What separates them is how long they stay available in the body. K1 is taken up mainly by the liver and cleared within hours. K2 as MK-7 stays in the blood much longer, so one capsule a day keeps your level steady. MK-4, the shorter K2 type, is used up quickly and needs several doses a day to do the same job. That is why most of what you see here is MK-7, and why it sits alongside the rest of our vitamin range.
Two label details worth checking
The first is the wording all-trans MK-7. Only this molecular shape is active; cheaper raw material can contain a share of the inactive cis form, and a good label says so plainly. The second is the dose. Most UK products sit between 90 and 200 mcg per capsule, while 75 mcg already covers the daily reference intake printed on the label. Higher is therefore not automatically better. Combinations with vitamin D3 products are common, because both are fat-soluble and fit the same daily moment.
How we choose the vitamin K we stock
We judge three things: the form, the dose and the combinations that make sense. For vitamin K that means we prefer K2 as all-trans MK-7 from fermentation, in doses of roughly 75 to 200 mcg rather than very high strengths, because steady daily intake is what the research is built on. We keep single-nutrient K2 next to D3 with K2 formulas, so you do not pay for an ingredient you already take. We buy directly from the brands, our compliance team checks every label before it goes live, and independent labs spot-check batches. You can read how we select brands and products.
Who this collection suits
Vitamin K supplements make the most sense for:
- People who rarely eat green vegetables or fermented food.
- Anyone already taking a higher-dose vitamin D3 and wanting K2 in the same routine.
- Adults over 50 who are thinking about bones and joints over the long term.
- People on a very low-fat diet, since fat-soluble nutrients are absorbed less well without any fat.
Be realistic about what this does. Vitamin K is not a supplement you feel: there is no lift in energy and nothing to notice day to day. It works quietly in clotting and in bone maintenance, so the value lies in taking a sensible amount consistently rather than in a strong dose now and then. Deficiency is uncommon in the UK, because a varied diet usually covers the need.
One thing to know before you buy: vitamin K interacts with anticoagulant medicines such as warfarin, which work by blocking its action. If you take one, speak to your GP or pharmacist first, and keep your intake stable rather than starting and stopping. Steady intake is what keeps your treatment predictable.
Frequently asked questions
What is vitamin K and what does it do?
Vitamin K is a fat-soluble vitamin, meaning it is absorbed together with fat from your food. It exists as K1 (phylloquinone) from green leafy vegetables and K2 (menaquinone) from fermented food such as natto and from some cheeses. Two health statements are approved for it in Europe: vitamin K contributes to normal blood clotting, and vitamin K contributes to the maintenance of normal bones. Your liver stores a reserve, so you do not depend on a perfect intake every single day.
How much vitamin K do adults need each day?
UK guidance works from body weight: roughly 1 microgram per kilogram a day, so about 70 mcg for a 70 kg adult. EFSA uses the same rule and translates it into fixed amounts per age group, shown below. Supplement labels use a Nutrient Reference Value of 75 mcg, which is why a 100 mcg capsule shows 133%.
| Age group | Adequate intake per day |
|---|---|
| 1 to 3 years | 12 mcg |
| 4 to 6 years | 20 mcg |
| 7 to 10 years | 30 mcg |
| 11 to 14 years | 45 mcg |
| 15 to 17 years | 65 mcg |
| Adults, incl. pregnancy | 70 mcg |
Do I still need a supplement if I eat plenty of greens?
Probably not for K1. A cooked portion of kale or spring greens easily passes the daily reference amount, and the NHS position is that a varied diet covers your vitamin K needs. A supplement is worth considering for different reasons: green vegetables rarely reach your plate, you eat almost no fermented food, you are already taking a higher-dose vitamin D3, or you follow a very low-fat diet. In those cases K2 as MK-7 is the form people usually choose.
Should I choose vitamin K1, MK-4 or MK-7?
The practical difference is how long each form stays available, which decides how often you have to dose. MK-7 is the form we stock most, because one capsule a day is enough.
| Form | Typical source | Stays active | Dosing |
|---|---|---|---|
| K1 | Green vegetables | Hours | Mainly from food |
| K2 as MK-4 | Animal, synthetic | Hours | Several times a day |
| K2 as MK-7 | Fermentation, natto | Days | Once a day |
Look for the words all-trans MK-7 on the label, since only that shape is active.
When is the best time to take vitamin K?
With a meal that contains some fat, such as breakfast with eggs or a main meal with olive oil. Vitamin K is fat-soluble, so a little fat improves how much you absorb. The time of day does not matter much with MK-7, because it stays in your blood for days; what matters is taking it at the same moment each day so you do not forget it. If you also take vitamin D3, the same meal is the simplest option.
Can I take vitamin K together with vitamin D3 and calcium?
Yes, and it is a common combination. Vitamin D contributes to the normal absorption and use of calcium, while vitamin K contributes to the maintenance of normal bones. They are separate approved statements, not one shared effect, so we do not present them as a single benefit. Practically speaking, a D3 with K2 capsule saves you a product, and calcium supplements are usually taken separately because the doses are much larger.
Is vitamin K2 suitable for vegans and people with a soy allergy?
Often, yes, but check the label. Most MK-7 is made by fermentation, traditionally of soybeans (natto) and increasingly of chickpea or other non-soy media. Refined MK-7 from soy fermentation usually contains no measurable soy protein, and some brands state this explicitly; if you have a diagnosed soy allergy, choose a product that names a soy-free source. Also check the capsule shell: plant-based HPMC or pullulan shells are vegan, while softgels can contain gelatine.
What if I take warfarin or another blood thinner?
Ask your GP or pharmacist before you start. Warfarin works by blocking vitamin K, so extra vitamin K from a supplement can change how well your medication works and shift your INR readings. The advice for people on warfarin is consistency: keep your vitamin K intake from food and supplements about the same each day rather than avoiding it or starting and stopping. If you take a newer anticoagulant, the interaction is different, so still check with your prescriber first.
