Vitamin D3 2,000 IU + K2 MK-7
In northern Europe the question is not “should I” but “how much”.
The short version
What it does It corrects a shortfall. In people who are deficient, it reduces the risk of respiratory infection.
What it does not do In someone whose level is normal, it brings nothing. Hence the rule: you test first, you do not guess.
What the studies say
Martineau’s individual participant data meta-analysis pooled 25 randomised trials, around 11,000 participants: vitamin D supplementation reduces the risk of acute respiratory infection. The benefit is very clearly concentrated in people who were deficient to begin with, and in daily or weekly dosing rather than large spaced-out doses.
In people with adequate status, the effect disappears. Quarterly megadoses have not shown the same benefit, and sometimes the opposite. The associated vitamin K2 has a mechanistic logic on calcium, but not the same level of evidence.
This is correcting a deficiency, not optimising. Hence the rule: test first, not after.
How to take it
Relevant October to April at our latitudes, and all year if you go out little, if your skin is dark, or after 60. Useless if your level is good and you get regular sun.
Get your 25(OH)D measured at the end of winter. Daily or weekly dosing rather than monthly. Always with a meal containing fat — it is a fat-soluble vitamin, and on an empty stomach you absorb far less.
Re-test after three months. The goal is to be in range, not at the top: beyond that there is no additional benefit and hypercalcaemia becomes possible.
What is inside
Cholecalciferol (D3), more effective than ergocalciferol (D2) at raising blood levels. Often combined with menaquinone-7 (K2). Oil base — olive, coconut, MCT.
Lichen-derived D3 exists for vegan diets; standard D3 comes from sheep lanolin. An oil form in drops can be dosed more finely than a tablet. For K2, MK-7 has a longer half-life than MK-4.
Self-medicating with 100,000 IU ampoules. Contraindicated in hypercalcaemia and sarcoidosis. K2 interacts with vitamin K antagonist anticoagulants: never without medical advice in that case.
Cautions
- Hypercalcaemia
- Sarcoidosis
- Vitamin K antagonists: K2 interferes
The three options
Lichen D3 + MK-7, in drops
K2 under the VitaMK7® label, in drops
A patented, traceable form, in organic olive oil, made in France. Two reservations: the dose is 3,000 IU rather than 2,000, and the D3 is not lichen-derived — no option in this aisle guarantees that today.
For whom — A plant-based diet, or needing to adjust the dose to a blood test.
D3 + K2 in drops
One drop = 2,000 IU + 50 µg of K2
Three ingredients: olive oil, D3, K2 as MK-7. MK-7 is the only form that stays in the blood long enough to act. The dropper lets you go down to one drop every other day.
For whom — Ordinary seasonal use.
D3 alone, in tablets
400 tablets, but no K2
2,000 IU per micro-tablet, 35,102 reviews. Two things to know: the ingredient list is only published in Italian, and it contains sucrose as a carrier. This is the price choice.
For whom — Tight budget — D3 is the essential part, K2 is a comfort extra.
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