Vitamin K is a fat-soluble vitamin, as K1 from leafy greens and K2 from fermented foods and gut bacteria, needed to make clotting and bone proteins1.
Needed to make prothrombin and other clotting proteins1.
Activates osteocalcin, a bone protein that may be involved in bone mineralization1.
Activates matrix Gla protein, studied for limiting abnormal calcification1.
Works as a coenzyme for the carboxylase that switches on vitamin K-dependent proteins1.
Gut bacteria make menaquinones (K2) that likely meet part of the body's need1.
| Food and serving | Amount |
|---|---|
| Natto, 3 oz (as K2, MK-7) | 850 µg |
| Collards, frozen, boiled, ½ cup | 530 µg |
| Turnip greens, frozen, boiled, ½ cup | 426 µg |
| Spinach, raw, 1 cup | 145 µg |
| Kale, raw, 1 cup | 113 µg |
| Broccoli, chopped, boiled, ½ cup | 110 µg |
| Soybeans, roasted, ½ cup | 43 µg |
| Soybean oil, 1 tbsp | 25 µg |
| Food and serving | Amount |
|---|---|
| Chicken breast, rotisserie, 3 oz (as MK-4) | 13 µg |
| Egg, hard boiled, 1 large (as MK-4) | 4 µg |
Vitamin K1 in vegetables is tightly bound to plant tissue, so eating greens with some fat helps absorption1. Amounts per serving from1.
Bacteria in the large bowel make long-chain menaquinones that likely supply some of the body's vitamin K1.
Most multivitamins contain some vitamin K, and stand-alone products use K1 or K2 (MK-4, MK-7)1.
A single vitamin K injection at birth is recommended to prevent vitamin K deficiency bleeding in babies1.
The same reference table draws the reference lines on your charts in Ayuvo. Needs differ in pregnancy and breastfeeding, which are not covered here.
| Age | Women | Men |
|---|---|---|
| 19–30 | 90 mcg | 120 mcg |
| 31–50 | 90 mcg | 120 mcg |
| 51–70 | 90 mcg | 120 mcg |
| 71+ | 90 mcg | 120 mcg |
AI (Adequate Intake) is used when there is not enough evidence for an RDA: an amount assumed to be enough. Per day, for adults1.
Signs like these have many possible causes. They are a reason to talk to a clinician, not to self-treat.
Deficiency is rare in adults and is usually limited to malabsorption disorders or medicines that interfere with vitamin K1.
No upper limit is set because no adverse effects from vitamin K in food or supplements have been reported1.
Prothrombin time, how long blood takes to clot, is the only clinically significant measure of vitamin K status and is mainly checked in people on anticoagulants1.
Labs use different units and ranges. Your clinician reads a result alongside your history and other tests.
Vitamin K is in most multivitamins and in products alone or combined with calcium, magnesium or vitamin D1.
The plant form; phytonadione is its synthetic version1.
A K2 form that is well absorbed and has a longer half-life than phytonadione1.
A short-chain K2 form that the body can also make from K11.
Supplements can interact with medicines. Talk to a clinician or pharmacist before you start one, especially at high doses.
Vitamin K1 (phylloquinone) comes mainly from green leafy vegetables and is the main dietary form. Vitamin K2 (menaquinones) comes from fermented foods like natto, some animal foods and gut bacteria. Both help activate clotting and bone proteins.
Vitamin K works against warfarin, so sudden changes in how much you eat can change how the medicine works. People on warfarin are usually advised to keep vitamin K intake consistent. Talk with your clinician about what that means for your diet.
Little vitamin K crosses the placenta and breast milk contains little, so newborns can develop vitamin K deficiency bleeding. A single injection at birth is recommended to prevent it.
Ayuvo charts vitamin K by day, week, month and year, with the reference lines from this page, personalised by age and sex where they differ. Supplements you log in Medications count too. Free, with no account.
Or read the code: Ayuvo is open source
Facts on this page come from these sources, checked on the dates shown. Intake numbers come from Ayuvo's shared reference table, which cites the sources marked for them.
General information, not medical advice. This guide is for healthy adults and does not cover pregnancy, breastfeeding, children or medical conditions. It cannot diagnose or treat anything. Talk to a clinician before starting high-dose supplements, or if you think you may have too little or too much of a nutrient. Spotted an error? Email us.