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Ingredient guide

How long does vitamin K2 take to work?

Written by the Full Measure editorial team, which sells supplements. Approved for publication by the Full Measure owners. Updated .

Drafted with AI assistance from the sources listed below. How we write these

Quick answer

Vitamin K2 reaches your blood within hours: K1 and MK-7 supplements both peak about 4 hours after a dose. MK-7 then lingers and builds up 7 to 8 fold with daily use. Bone density changes, where trials found any, were small and took 6 months to 2 years to show.1,2

Key facts

  • Body stores of vitamin K are small, because it is used and cleared quickly.3
  • In the 3-year MK-7 bone trial, measurements were taken after 1, 2 and 3 years.4
  • MK-7 activated more osteocalcin than K1 in a head-to-head study.1
  • In volunteers kept on a warfarin-like medicine, small daily doses of MK-7 shifted clotting tests within the six weeks of the study.5

The first hours

Supplements of K1 and of MK-7 are both absorbed well, with blood levels peaking about 4 hours after a dose.1

Like other fat-soluble vitamins, vitamin K is absorbed along with dietary fat, carried from the gut to the liver in fat particles, and passed on to other tissues, bone among them.3

How long it stays in the body

K1 is used and cleared quickly. The body keeps only about 30 to 40% of a dose, while about 20% leaves in urine and 40 to 50% in stool via bile, which is why the body's stores of vitamin K are small.3

MK-7 stays in the blood far longer than K1, so its levels are steadier and build up 7 to 8 fold with daily use.1,3

So the two forms behave differently from day to day. K1 is cleared quickly after each dose, while MK-7 settles into a steadier, higher level with daily use.1,3

Weeks: markers of vitamin K status

In 42 healthy adults, MK-7 at amounts around the EU daily reference intake activated more osteocalcin and matrix Gla protein, signs of better vitamin K status outside the liver.6

These markers, the share of osteocalcin and matrix Gla protein that has been activated, are what move first. They show the vitamin is reaching bone and blood vessels. They do not, on their own, show a change in bone.3,6

Years: bone density

Bone density changes slowly, so vitamin K bone trials last 6 months to 3 years. In a 2019 pooled analysis, the differences seen at 6 months to 2 years were all under 2%, and the spine results lost statistical significance when lower quality trials were set aside.2,4

MK-7 may help maintain bone mineral density in women after menopause*2,3,4

Early evidence

One three-year randomized trial in 244 healthy women after menopause found that 180 mcg of MK-7 a day slowed the usual decline in bone mineral content and density at the lower spine and the femoral neck, though not at the total hip, and bone strength measures held up better than on placebo. It came from a single vitamin K research group, and other trials of vitamin K have found no effect on bone density, so the evidence is early.

Amount studied: 180 mcg of MK-7 a day for three years

A marker moving is not the same as bone changing. In a 12-month trial of 381 women after menopause, K1 and MK-4 shifted osteocalcin but left bone density where it was.3

If you take warfarin

For people on warfarin and similar medicines, the timescale is short. Vitamin K changes how these medicines work, and in a study of volunteers kept on a warfarin-like medicine, daily MK-7 shifted their clotting test within six weeks. Do not start or stop vitamin K without your doctor.5,7

Questions people ask

How long does vitamin K2 stay in the body?

MK-7 stays in the blood much longer than K1 and builds up with daily use, so its levels are steadier. K1 is cleared quickly: the body keeps only 30 to 40% of a dose. The sources we used do not give an exact half-life for MK-7.1,3

How long before vitamin K2 does anything for bones?

Bone trials of MK-7 ran for up to three years, with measurements at 1, 2 and 3 years, and the evidence that K2 changes bone density is still early. Do not expect a quick change.2,4

Do I need to take K2 every day?

The trials gave it daily, and MK-7's long stay in the blood means levels build with regular use. If you take warfarin, the amount you take each day has to stay steady and be agreed with your doctor.1,4,7

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Sources

  1. Schurgers LJ, et al. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. 2007;109(8):3279-3283. Opened 2026-10-07.
  2. Mott A, et al. Effect of vitamin K on bone mineral density and fractures in adults: an updated systematic review and meta-analysis of randomised controlled trials. Osteoporos Int. 2019;30(8):1543-1559. Correction: Osteoporos Int. 2020;31(11):2269-2270. Opened 2026-10-07.
  3. National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. Updated March 29, 2021. Opened 2026-10-07.
  4. Knapen MH, et al. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. 2013;24(9):2499-2507. Opened 2026-10-07.
  5. Theuwissen E, et al. Effect of low-dose supplements of menaquinone-7 (vitamin K2) on the stability of oral anticoagulant treatment: dose-response relationship in healthy volunteers. J Thromb Haemost. 2013;11(6):1085-1092. Opened 2026-10-07.
  6. Theuwissen E, et al. Low-dose menaquinone-7 supplementation improved extra-hepatic vitamin K status, but had no effect on thrombin generation in healthy subjects. Br J Nutr. 2012;108(9):1652-1657. Opened 2026-10-07.
  7. Office of Dietary Supplements, National Institutes of Health. Vitamin K: Fact Sheet for Consumers. Updated March 22, 2021. Opened 2026-10-07.

*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.