Vitamin K
Needed for blood clotting and for putting calcium into bones.
If you are short of it
Possible signs
- Easy bruising or bleeding
- Slow wound healing
- Fragile bones, easy fractures
These signs are common and have many other causes. They are clues, not proof; a blood test and a doctor can tell.
Who is more at risk
Newborns (a vitamin K injection is routinely given at birth), people with fat malabsorption or bile-duct disease, long-term antibiotic or anticonvulsant use.
Foods rich in Vitamin K
| Food | Serving | Amount | women 19–50 | men 19–50 |
|---|---|---|---|---|
| Parsley (as in tabbouleh) | ½ cup chopped (30 g) | 492 | 547% | 410% |
| Spinach (cooked) | ½ cup (90 g) | 444 | 493% | 370% |
| Kale (cooked) | ½ cup (65 g) | 270 NIH | 300% | 225% |
| Broccoli (cooked) | ½ cup (80 g) | 110 NIH | 122% | 92% |
| Molokhia (cooked) | 1 cup (90 g leaves) | 94 | 104% | 78% |
| Cabbage | ½ cup cooked or 1 cup raw | 82 | 91% | 68% |
| Okra (cooked) | ½ cup (80 g) | 32 | 36% | 27% |
| Bok choy (cooked) | ½ cup (85 g) | 29 | 32% | 24% |
| Kiwi | 1 medium | 28 | 31% | 23% |
| Avocado | half a fruit (100 g) | 21 | 23% | 18% |
| Green peas | ½ cup cooked (80 g) | 21 | 23% | 18% |
| Edamame (green soybeans) | ½ cup shelled (80 g) | 21 NIH | 23% | 18% |
| Pomegranate | ½ cup seeds (87 g) | 14 | 16% | 12% |
| Tomato | 1 medium | 10 | 11% | 8.3% |
Unit: mcg. Share of the daily amount. Values marked NIH were checked against the food tables of the NIH Office of Dietary Supplements; the others are approximate and unchecked. Real foods vary with variety, brand, soil and cooking.
As a supplement
K1 (phylloquinone) comes from plants; K2 (menaquinones) from fermented and animal foods. Most healthy adults do not need a supplement.
Too much
No upper limit has been set, but vitamin K changes the dose of warfarin: never start or stop supplements without telling the clinic that manages your blood thinner.
How much you need each day
| Group | Recommended | Upper limit |
|---|---|---|
| Infants 0–6 months | 2 | — |
| Infants 7–12 months | 2.5 | — |
| Children 1–3 years | 30 | — |
| Children 4–8 years | 55 | — |
| Children 9–13 years | 60 | — |
| Boys 14–18 years | 75 | — |
| Girls 14–18 years | 75 | — |
| Men 19–30 years | 120 | — |
| Women 19–30 years | 90 | — |
| Men 31–50 years | 120 | — |
| Women 31–50 years | 90 | — |
| Men 51–70 years | 120 | — |
| Women 51–70 years | 90 | — |
| Men over 70 | 120 | — |
| Women over 70 | 90 | — |
| Pregnant 14–18 years | 75 | — |
| Pregnant 19–30 years | 90 | — |
| Pregnant 31–50 years | 90 | — |
| Breastfeeding 14–18 years | 75 | — |
| Breastfeeding 19–30 years | 90 | — |
| Breastfeeding 31–50 years | 90 | — |
Unit: mcg. US/Canada Dietary Reference Intakes (National Academies), as summarised by the NIH Office of Dietary Supplements. Other countries’ values differ slightly. These are amounts for healthy people, not treatment doses.
Interactions
Take care · Vitamin E
High-dose vitamin E (above about 400 IU a day) can interfere with vitamin K and blood clotting — important if you take a blood thinner.
Works together · Vitamin D
Vitamin K works with vitamin D and calcium to place calcium in bones. Evidence for K2 supplements is still limited.
Medicines and habits to mention to your doctor
Warfarin (blood thinner)
Keep vitamin K intake steady (do not suddenly eat much more or less green vegetables) and tell the clinic before starting any supplement; high-dose vitamin E can add to bleeding risk.
Anti-seizure medicines (phenytoin, carbamazepine, valproate)
They can lower folate, vitamin D, vitamin K and biotin. Ask about bone health and folate, especially before pregnancy.
Fat blockers (orlistat) and bile-acid binders
They reduce absorption of fat-soluble vitamins A, D, E and K. Take a multivitamin at a different time, at least 2 hours apart.
Page updated: 2026-10-08 · By Prof. E. Shalaan, Applied Sciences and AI (ASAI)