Vitamin K2
Also known as: Menaquinone, MK-7, MK-4, K2
Directs calcium into bone rather than arteries — which is why it belongs next to vitamin D3, and why taking D3 in quantity without it is the part most people get wrong.
Substance family
Vitamins, minerals, amino acids and enzymes. The recurring pattern: correcting an actual deficiency helps, supplementing beyond a normal level generally does not.
Effects on
Which outcomes this substance acts on — descriptive, not a recommendation.
Strain profile
Where this substance is most likely to hit — a rough orientation, individually dependent on dose, duration and predisposition.
Dosing & protocols by goal
Rough orientation ranges as reported in harm-reduction literature — not an individual treatment plan. Doses are individual and open-ended; frequency depends on the ester or half-life.
Alongside vitamin D3
SupportDose
100–200 mcg MK-7
Frequency
1× / day with a meal containing fat
Cycle length
Ongoing, as long as D3 is taken
MK-7 rather than MK-4: the longer half-lifehalf-lifeHow long it takes for half the substance to leave the body — it determines dosing frequency, not duration of effect. means one daily dose maintains a level, where MK-4 needs several.
Side effect & countermeasure
Typical problems and what you can do to reduce harm — at a glance. Does not replace medical monitoring.
Problem
Taking high-dose D3 without K2
Countermeasure
D3 increases how much calcium is absorbed; K2 governs where it ends up. The two belong together, particularly at the doses commonly used.
Problem
On an anticoagulant
Countermeasure
Vitamin K directly opposes warfarin-type anticoagulants and will interfere with their control. This is a conversation with the prescribing doctor before starting, not after.
Overview
Vitamin K2 is here for one reason: it is the half of the vitamin D3 story that usually gets left out.
D3 raises how much calcium the gut absorbs. K2 determines where that calcium goes — into bone, or into soft tissue and arterial walls. Taking the first without the second increases the supply without directing it.
Mechanism of Action
K2 activates two calcium-binding proteins. Osteocalcin puts calcium into bone. Matrix Gla protein keeps it out of arterial walls. Both are inactive without vitamin K.
That is the whole mechanism, and it explains why the pairing with D3 matters more than the dose of either.
MK-7 or MK-4
The two forms behave differently in a way that decides how you take them.
MK-7 has a half-life of around three days. One daily dose maintains a steady level, and 100–200 mcg is the usual range.
MK-4 clears within hours. Maintaining a level needs several doses a day at much higher amounts, which is how it is used in Japanese clinical work but not how supplements are typically dosed.
For anyone taking this alongside D3, MK-7 once daily is the practical form.
Why it belongs in this context
Two reasons specific to this field.
Vitamin D3 is widely taken here, frequently at high doses, and often for years — exactly the pattern where the direction of calcium starts to matter.
And the cardiovascular side is already under pressure: lipids suppressed by androgens, blood pressure elevated, hematocrit raised. Arterial calcification is slow, silent, and not something the panel most people run will show. K2 is cheap insurance against one contributor to it.
Side Effects & Risks
- Very well tolerated; no established toxic level for K2
- Interacts with warfarin-type anticoagulants — vitamin K is what those drugs work against, and adding it undermines their control
- Fat-soluble, so it needs to be taken with food containing fat to be absorbed
Blood Work & Monitoring
- No routine marker in general use
- If on an anticoagulant, INR — and that belongs with the prescribing physician
Harm-Reduction Notes
- Take it with D3, not instead of it — they do different jobs
- With a meal containing fat, or most of it passes through
- MK-7 for once-daily dosing
- On any anticoagulant, ask first. This is the one genuinely important interaction on this page
Legal status by region
Regulation differs considerably between jurisdictions and changes over time. This is a rough orientation, not legal advice — check the rules that apply where you are.
| Region | Regulatory status |
|---|---|
| United States | Dietary supplement |
| EU / UK | Food supplementFreely available, subject to labelling and claims rules. |
| Canada / Australia | Freely available |
| Parts of Asia, Latin America & Middle East | Freely available |
| Competitive sport | Not prohibitedSupplement contamination remains a practical risk for tested athletes. |