Vitamin K2 plays a unique role: it directs where calcium goes in the body. Without it, calcium absorbed thanks to vitamin D risks being deposited in the wrong places — arteries, kidneys, soft tissue — instead of strengthening bone.

K2 activates two key proteins: osteocalcin, produced by bone-building cells, which “captures” calcium and fixes it into the bone matrix; and matrix Gla-protein (MGP), which helps prevent calcium from depositing in artery walls — the mechanism by which K2 contributes to cardiovascular health.

The MK-7 (menaquinone-7) form is the most effective form of vitamin K: it has a 72-hour half-life versus 1-2 hours for vitamin K1, meaning a single daily dose maintains stable circulating levels; it is around 50 times more effective than K1 at activating osteocalcin in bone; and unlike K1, which is captured mostly by the liver, MK-7 circulates in the blood for longer and reaches peripheral tissues — bone, arteries and cartilage.

Taking vitamin D3 without K2 is an incomplete approach. Vitamin D3 increases intestinal calcium absorption by 30-40% (without it, only 10-15% of dietary calcium is absorbed), while K2 directs that calcium toward bone (via osteocalcin) and away from arteries (via MGP). Without K2, the extra calcium absorbed thanks to D3 can end up depositing in the arteries — the so-called “calcium paradox”.

Dr Jacob’s uses a Norwegian-origin MK-7, produced by bacterial fermentation, guaranteeing the 100% trans (all-trans MK-7) form — the only biologically active one, whereas some cheap MK-7 products contain up to 30% of the inactive cis form. It offers superior stability against heat, light and stomach acid, is fully vegan (produced by fermentation, no animal components), and each drop delivers 20 µg, in line with expert recommendations of 45-200 µg/day depending on needs.

Take 1 to 5 drops per day (20 to 100 µg), with a meal containing fat. The drop format allows precise adjustment of dosage to your needs. Recommended pairings: vitamin D3 (the reference D3+K2 protocol for bone health), magnesium (essential cofactor of bone metabolism and vitamin D activation), and collagen.

Vitamin K2 is contraindicated for people on vitamin K antagonist anticoagulants (warfarin, acenocoumarol, fluindione), as K2 opposes the action of these medicines — consult your doctor. Direct oral anticoagulants (DOACs) such as rivaroxaban or apixaban are not affected by this interaction.

Should K2 always be taken together with D3?

It’s strongly recommended. D3 increases calcium absorption, and K2 directs it toward the bones. Without K2, excess calcium may end up depositing in the arteries.

Is K2 useful without a vitamin D3 supplement?

Yes. Even without a D3 supplement, K2 activates osteocalcin and MGP, and is beneficial for anyone consuming calcium through food or supplements.

How long does a bottle last?

At 2 drops a day, a bottle lasts several months — the drop format is very economical.

Herba Barona is an independent specialist supplement shop in the heart of Paris — established in 2006. What you order is genuinely on our shelves: we ship from our own stock, with no dropshipping and no long waits.

Visit us at 10 rue Théophile Roussel, Paris 12 — or use Click & Collect and pick up your order in-store. We also deliver across France and Europe. Friendly, expert advice in English from our team.

Where is the shop?

Herba Barona is at 10 rue Théophile Roussel, 75012 Paris — a two-minute walk from Ledru-Rollin (line 8), close to Bastille. Open Tuesday to Saturday, 9:30 am–6:30 pm.

Can I order online or collect in store?

Yes. We ship across France and Europe under the same conditions as our French store, or choose Click & Collect to pick up your order for free at our Paris shop.