Ten years ago a vitamin D supplement contained vitamin D. Today a large share of the category pairs it with vitamin K2, usually as MK-7, and often with a supporting cast of boron, magnesium or calcium. The pairing is presented as obvious, and the reasoning behind it is rarely spelled out on the bottle.
There is a legitimate rationale, there are authorised claims for both nutrients, and there is also more marketing confidence around the combination than the evidence strictly supports. This guide separates those three things, explains what MK-7 means, and flags the one interaction that matters more than anything else on the label.
Why D3 and K2 are sold together
The reasoning usually offered is that both nutrients are involved in how the body handles calcium, and that taking one without the other leaves that picture incomplete. Vitamin D has an authorised claim relating to normal blood calcium levels and to the maintenance of normal bones. Vitamin K has an authorised claim relating to the maintenance of normal bones and to normal blood clotting.
Those are two separate authorised claims for two separate nutrients, and that distinction is the important one. UK claims rules do not include an authorised claim for the combination doing something that neither does alone. When you see that argument made forcefully in marketing copy, it is running ahead of what the register permits.
None of which makes the pairing unreasonable. It means a well-run label should present it as two nutrients each carrying their own claim, and let you decide, rather than implying a synergy it is not allowed to assert.
What the authorised claims actually say
It is worth reading the permitted wording, because it is more modest and more specific than the paraphrases that circulate online.
- Vitamin D contributes to the maintenance of normal bones and normal teeth, to normal muscle function, to the normal function of the immune system, and to normal blood calcium levels.
- Vitamin K contributes to the maintenance of normal bones and to normal blood clotting.
- Calcium is needed for the maintenance of normal bones and teeth.
Every one of those is about maintaining normal function in healthy people. None of them says a supplement builds bone, prevents fracture, treats osteoporosis or directs calcium anywhere in particular. Those stronger statements are medicinal claims, and a food supplement cannot make them.
MK-4 and MK-7: why the menaquinone number matters
Vitamin K2 is not one substance. It is a family of menaquinones distinguished by the length of their side chain, written as MK- followed by a number. MK-4 and MK-7 are the two used in supplements, and they differ in how long they persist in circulation, MK-7 being the longer-lived of the pair. That is the main practical reason MK-7 dominates the once-daily category.
A label that says vitamin K2 and stops has told you the family but not the member, which makes comparison between products impossible. Ours states 80 µg of vitamin K2 as menaquinone-7 per two-capsule serving. Our multivitamin separately lists 65 µg of vitamin K as phylloquinone alongside 10 µg of MK-7, printed as two rows because they are two different things.
You may also see MK-7 described as all-trans or natto-derived. Those are real distinctions relating to isomer purity and source, and they are fair questions to ask a manufacturer. They are not something the front of a bottle can settle.
The two-capsule serving
Combination products are where serving-size confusion does the most damage, because there are several numbers to misread at once. Our panel states a two-capsule serving and thirty servings per bottle. Every amount printed — 50 µg of vitamin D3, 80 µg of K2, 550 mg of PEA, 3 mg of boron, 100 mg of calcium — is the total delivered by both capsules together.
Take one capsule and you get roughly half of each. Compare our per-serving figures against another brand's per-capsule figures and you will draw exactly the wrong conclusion about which is stronger. Convert both to a full daily serving before comparing anything.
The same arithmetic applies to value. Sixty capsules at two per day is a thirty-day supply, so the comparison is price per day, not price per bottle.
Boron, PEA and calcium: the rest of the panel
Three other ingredients sit on this panel, and honesty about them matters more than enthusiasm.
Calcium, at 100 mg as tricalcium phosphate, is 25% of the NRV. It carries the authorised claim above. It is a contribution to daily intake rather than a substitute for a calcium supplement if you have been advised to take one.
Boron, at 3 mg as boron glycinate, is a trace element with no authorised UK health claim. We state the amount and attach nothing to it.
PEA, palmitoylethanolamide, at 550 mg, is the largest single amount on the panel and also has no authorised UK health claim. It is a fatty acid amide that the body produces itself and that appears in some foods. You will find it discussed in research literature; you will not find an approved claim for it, and we do not make one. The amount is published so you can look into it yourself and reach your own view.
The warfarin question
This is the section to read even if you skip the rest. Vitamin K is central to blood clotting, and anticoagulant medicines of the warfarin type work by interfering with that pathway. Changing your vitamin K intake can change how well that medicine controls your clotting, which is measured as your INR.
If you take warfarin or any similar anticoagulant, do not start a vitamin K-containing supplement on your own. Speak to your GP, your pharmacist or your anticoagulation clinic first. That is not a defensive formality; it is the single most clinically important thing on this product's label, and our own bottle carries the caution.
Two further cautions from the same panel. Speak to a doctor before use if you have a calcium disorder. And vitamin D here is supplied at 1000% of the NRV, so add up your total across every product you take, including any multivitamin and anything prescribed. The product is not suitable for children.
Taking it with food that contains fat
Vitamin D and vitamin K are both fat-soluble, and PEA is a fatty acid amide. Our directions therefore specify a daily serving taken with a meal containing some fat. It does not need to be a large meal or a particularly fatty one — the usual fat content of an ordinary breakfast or lunch is the sort of thing meant.
Beyond that, the most useful habit is consistency. A supplement taken at a predictable point in the day, attached to a meal you always eat, is one you will actually keep taking. Storage matters too: our label asks for a cool, dry place away from direct sunlight, with the cap closed.
If you are starting more than one new supplement, introduce them one at a time and leave a gap between them. If something does not agree with you, that is the only way to know which product was responsible.
What to check before buying a D3 and K2 product
A short list covers the category.
- Serving size — one capsule or two, and how many servings in the bottle.
- Vitamin D amount in micrograms, converted from IU if necessary, and totalled against everything else you take.
- Which K2 — MK-7 or MK-4, named rather than left as vitamin K2.
- What else is in it, and whether each additional ingredient is given an amount or just a mention.
- The cautions, and specifically the anticoagulant warning.
- Whether claims are authorised ones, or whether the page is promising bone density and artery health in language no supplement is allowed to use.
Frequently asked questions
Do I need to take K2 with vitamin D3?
Not necessarily. Each nutrient has its own authorised UK claim and there is no authorised claim for the combination doing something extra. The pairing has a plausible rationale and is widely sold, but a straight vitamin D product remains a perfectly reasonable choice, particularly if you take an anticoagulant and vitamin K is best avoided.
What is MK-7 and how does it differ from MK-4?
Both are forms of vitamin K2, distinguished by side-chain length. MK-7 stays in circulation longer than MK-4, which is why it suits once-daily products and is the form on our label at 80 µg per two-capsule serving. A label that names the menaquinone lets you compare products; one that says only vitamin K2 does not.
Can I take vitamin K2 if I am on warfarin?
Not without medical advice. Vitamin K directly affects the pathway warfarin acts on, and changing your intake can alter your INR control. Speak to your GP, pharmacist or anticoagulation clinic before starting any vitamin K-containing supplement, including ours.
What is PEA doing in a vitamin D supplement?
PEA, palmitoylethanolamide, is included at 550 mg per serving and is the largest single amount on our panel. It has no authorised UK health claim, so we publish the amount and make no statement about what it does. If you want to look into it, the exact amount and form are on the label precisely so that you can.
Before choosing a supplement
- Read the complete current label, including the active and the other ingredients.
- Compare the daily serving rather than the number printed on the front of the bottle.
- Add up every source of the same nutrient across your whole routine.
- Ask a pharmacist or qualified healthcare professional about medicines, pregnancy, breastfeeding, surgery or an existing condition.
- Remember that food supplements do not replace a varied, balanced diet and a healthy lifestyle.
Related guides on this formula
- Vitamin D in the UK: how much to take in autumn and winter
- A UK winter wellbeing checklist that stays realistic
View the Vitamin D3+K2 Advanced label, the full ingredient panel and current purchase options.
Also useful: RevaHealth Journal · full range · Ingredients · Contact.
References and further reading
This article is general educational information, not medical advice. Food supplements are not medicines and are not intended to diagnose, treat, cure or prevent disease. Always read the complete physical label before use, and speak to your GP or pharmacist if you are unsure whether a supplement is right for you.
