Quick answer
There is no separate target for K2. The adequate intake for all vitamin K is 120 mcg a day for men and 90 mcg for women, and most US adults reach it from food. Trials of MK-7 have used 10 to 360 mcg a day, with 180 mcg in the longest bone trial. No upper limit is set.1,2,3
Key facts
- The Daily Value on labels is 120 mcg, so a 120 mcg serving shows as 100% of the Daily Value.1
- US women average 122 mcg and men 138 mcg of vitamin K a day from food alone.1
- Some vitamin K supplements contain 4,050 mcg, more than 30 times the Daily Value.1
- The 45 mg of MK-4 used as a medicine in Japan is 45,000 mcg, about 375 times the Daily Value.1
Adequate intake by age
| Age or stage | Adequate intake |
|---|---|
| Birth to 6 months | 2.0 mcg |
| 7 to 12 months | 2.5 mcg |
| 1 to 3 years | 30 mcg |
| 4 to 8 years | 55 mcg |
| 9 to 13 years | 60 mcg |
| 14 to 18 years, including pregnancy and breastfeeding | 75 mcg |
| Men 19 and older | 120 mcg |
| Women 19 and older, including pregnancy and breastfeeding | 90 mcg |
There is no separate recommended amount for vitamin K2. The adequate intake covers all forms of vitamin K, and it was set from what healthy people eat, because there was not enough evidence to work out a precise requirement.1
An adequate intake is a softer figure than a recommended dietary allowance. It reflects what healthy people already eat, and the menaquinones made by gut bacteria cover part of the need in amounts no one has yet measured.1
Amounts used in studies
Trials have used 180 mcg of MK-7 a day for three years, 1 mg of K1 a day for a year, and 45 mg of MK-4 a day, an amount used as a prescription medicine in Japan.1,3
| Who was studied | Form and daily amount | What was measured |
|---|---|---|
| 244 healthy women after menopause, 3 years | MK-7, 180 mcg | Bone density and bone strength |
| 42 healthy adults aged 18 to 45 | MK-7, 10 to 360 mcg | Vitamin K status and a lab measure of clotting |
| 381 women after menopause, 12 months | K1, 1 mg, or MK-4, 45 mg | Bone density and a bone protein |
The MK-7 amounts in these trials, 10 to 360 mcg, are of the same order as the adequate intake for all vitamin K. The K1 and MK-4 amounts are many times higher: 1 mg is 1,000 mcg, and 45 mg is a prescription dose.1,2
Reading a K2 label
The Daily Value for vitamin K on labels is 120 mcg for adults and children aged 4 and older. Food labels only have to list vitamin K when it has been added.1
Multivitamins usually contain less than 75% of the Daily Value for vitamin K, while vitamin K supplements vary much more, some providing 4,050 mcg.1
K2 products may name the form as MK-4 or MK-7, the two menaquinones used in supplements. Watch the units: a product listing 45 mg of MK-4 holds 45,000 mcg, far beyond the microgram amounts in most MK-7 products.1,4
K2 with D3: is there a ratio?
No official body sets a ratio of vitamin K2 to vitamin D3. The two amounts are set separately: 90 to 120 mcg of vitamin K a day for adults, and 15 to 20 mcg (600 to 800 IU) of vitamin D.1,5
Vitamin K is sold alone or combined with a few other nutrients, most often calcium, magnesium or vitamin D.1,4
Is there a maximum?
No upper limit has been set for vitamin K, because of its low potential for harm: the expert panel that sets intakes found no reported adverse effects from vitamin K in food or supplements in people or animals. This does not apply to anyone taking warfarin or a similar blood thinner.1,4
For anyone on warfarin or a similar blood thinner, no amount is automatically fine. In a study of volunteers kept on a warfarin-like medicine, as little as 10 to 20 mcg of MK-7 a day shifted the clotting test enough to matter in some of them.6
Questions people ask
Is 100 mcg of K2 a day enough?
For most adults, 100 mcg is close to the adequate intake for all vitamin K, which is 90 mcg for women and 120 mcg for men. Most people already get about that much from food, so a supplement adds to what you eat rather than filling a known gap.1,4
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Sources
- National Institutes of Health, Office of Dietary Supplements. Vitamin K: Fact Sheet for Health Professionals. Updated March 29, 2021. Opened 2026-10-07.
- 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.
- 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.
- Office of Dietary Supplements, National Institutes of Health. Vitamin K: Fact Sheet for Consumers. Updated March 22, 2021. Opened 2026-10-07.
- National Institutes of Health, Office of Dietary Supplements. Vitamin D: Fact Sheet for Health Professionals. Updated June 27, 2025. Opened 2026-10-07.
- 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.
This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.