Vitamin K: K1 vs K2, How Much You Need, and the One Warning (2026)
K1 and K2 are both vitamin K. K1 comes from leafy greens, and most of it goes to the liver, where vitamin K helps make clotting proteins. K2 comes from natto and, in small amounts, cheese, eggs and meat; its MK-7 form lasts longer in the blood. Adults need 90 mcg (women) or 120 mcg (men) a day, both kinds together, and most U.S. diets have enough. The one warning: on warfarin, keep your vitamin K steady.
By Erin Rose Updated October 5, 2026 How we score
K1 vs K2 at a glance
| K1 (phylloquinone) | K2 (menaquinones) | |
|---|---|---|
| Comes from | Green leafy vegetables and some plant oils | Made mostly by bacteria: natto, and small amounts in cheese, eggs and meat |
| Where it goes | Mostly to the liver, where vitamin K helps make clotting proteins | Spread more widely through the body |
| How long it lasts | Shorter | MK-7 stays in the blood much longer, so daily doses build up |
| Share of the vitamin K you eat | Most of it | Up to about a quarter |
| Counts toward the daily need | Yes | Yes; the target counts both |
| As a supplement | K1 pills, or in K blends | Mostly MK-7, often 100 mcg |
K1 and K2 in food
Most vitamin K in food is K1, from greens. Natto is the one rich K2 food: about 850 mcg of MK-7 in 3 ounces. K2 makes up to about a quarter of the vitamin K people eat (Beulens 2013).
| Item | Value |
|---|---|
| Natto, 3 ounces | 850 mcg |
| Collards, frozen, boiled, ½ cup | 530 mcg |
| Turnip greens, frozen, boiled, ½ cup | 426 mcg |
| Spinach, raw, 1 cup | 145 mcg |
| Kale, raw, 1 cup | 113 mcg |
| Broccoli, boiled, ½ cup | 110 mcg |
| Chicken breast, rotisserie, 3 ounces | 13 mcg |
| Ground beef, broiled, 3 ounces | 6 mcg |
| Chicken liver, braised, 3 ounces | 6 mcg |
| Ham, 3 ounces | 4 mcg |
| Cheddar cheese, 1½ ounces | 4 mcg |
| Egg, hard boiled, 1 large | 4 mcg |
How much vitamin K you need
| Adults 19 and older | A day |
|---|---|
| Men | 120 mcg |
| Women, including pregnancy and breastfeeding | 90 mcg |
These are Adequate Intakes, not RDAs: there was not enough data to set an average requirement, so they are based on what healthy people eat, and they were set from K1 (NIH; Beulens 2013). There is no separate target for K2. Most U.S. diets have enough; adults average 122 mcg a day (women) and 138 mcg (men) from food (NIH). One cup of raw spinach has 145 mcg. No upper limit is set for vitamin K.
K2 supplements are dosed differently. For MK-7 and MK-4 label doses, see how much K2 a day.
The one warning: warfarin
If you take warfarin or a similar drug, keep your vitamin K steady. These drugs work against vitamin K, and sudden changes in vitamin K from food or supplements can raise or lower their effect (NIH). You don’t need to cut out greens; keep the amount steady. K2 pills are a different matter. When volunteers on a warfarin-type drug took a small daily MK-7 pill, their clotting test (INR) fell, and the study’s authors told people on these drugs to avoid MK-7 supplements (Theuwissen 2013). Ask the doctor who manages your blood thinner before you take any vitamin K pill.
Apixaban, rivaroxaban, dabigatran and edoxaban are different: they do not act through vitamin K (Rose 2018). Your doctor should still know about any supplement you take.
Vitamin K deficiency
Vitamin K deficiency means blood that clots too slowly, and bleeding in severe cases (NIH). It is rare in adults. It mostly affects newborns, people who don’t absorb fat well, and people on drugs that block vitamin K. Lab markers of low K2 status are research tests, not a diagnosis.
If you want a supplement
Most people don’t need one. If you want K2, plain MK-7 is the usual choice (MK-7 vs MK-4).
Every K2 we score · How much K2
K2 guides
- Vitamin K2: what it does and what trials found
- The best vitamin K2, scored
- How much K2 a day
- MK-7 vs MK-4
- Vitamin D with or without K2
Questions
Do I need both K1 and K2?
Not as separate pills. The daily target counts K1 and K2 together, and most U.S. diets have enough vitamin K. A cup of raw spinach has 145 mcg of K1, more than a day’s target. If you want a K2 supplement, plain MK-7 is the usual choice.
Is vitamin K the same as K2?
K2 is one kind of vitamin K. “Vitamin K” on a food label or in the daily target means K1 and K2 together; most vitamin K in food is K1.
Sources
- NIH Office of Dietary Supplements. Vitamin K fact sheet for health professionals (Adequate Intakes, food table, intakes, upper limit, warfarin, deficiency; updated March 29, 2021; read October 5, 2026).
- Beulens JW, et al. The role of menaquinones (vitamin K2) in human health. Br J Nutr. 2013. PubMed 23590754
- Schurgers LJ, Vermeer C. Differential lipoprotein transport pathways of K-vitamins in healthy subjects. Biochim Biophys Acta. 2002. PubMed 11960685
- Schurgers LJ, et al. Vitamin K-containing dietary supplements: comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood. 2007. PubMed 17158229
- Theuwissen E, et al. Effect of low-dose supplements of menaquinone-7 on the stability of oral anticoagulant treatment. J Thromb Haemost. 2013. PubMed 23530987
- Rose DK, Bar B. Direct oral anticoagulant agents. J Stroke Cerebrovasc Dis. 2018. PubMed 29753603
This page is for information. It is not medical advice.