Vitamin
Vitamin K
This article is written from cited public sources but has not yet been signed off by a qualified expert. Use it as general background only, and check important details with a health professional.
Vitamin K helps blood clot and supports bone health. Green leafy vegetables are the main source. People taking warfarin need to keep their vitamin K intake steady and should talk to their doctor before changing diet or supplements.
What is Vitamin K?
Vitamin K is a family of fat-soluble compounds. Phylloquinone (vitamin K1) comes mainly from green leafy vegetables. Menaquinones (vitamin K2) are made by bacteria and are found in some animal and fermented foods.[1]
Its role in the body
Important food sources
- Green leafy vegetables such as spinach (palak), methi leaves, amaranth, mustard greens (sarson) and cabbageThe main dietary source.
- Vegetable oilsContain some vitamin K.
- Some fruits
- Meat, dairy foods and eggsSmall amounts of vitamin K1, modest amounts of K2.
- Fermented foodsSome contain vitamin K2.
Recommended dietary intake
| Group | Amount | Basis | Region |
|---|---|---|---|
| Men 19+ yearsUS Food and Nutrition Board value for healthy people; Indian reference value to be added after verification. | 120 mcg/day[1] | AI | USA |
| Women 19+ years, including pregnancy and breastfeedingUS Food and Nutrition Board value for healthy people; Indian reference value to be added after verification. | 90 mcg/day[1] | AI | USA |
Signs sometimes associated with low levels
Why symptoms alone cannot confirm a deficiency
Signs like tiredness, weakness, hair fall or low mood are very common and have many possible causes, such as poor sleep, stress, infections, thyroid problems or other illnesses.
The same sign can come from several different nutrients, or from no nutrient problem at all.
Only a qualified clinician, using your history, an examination and, when needed, lab tests, can say whether a deficiency is present. This app cannot diagnose a deficiency from symptoms or from BMI.
Easy bruising or bleeding has many causes, including medicines and blood disorders, and needs medical assessment.
Tests a clinician might consider
- Vitamin K status is not usually tested except in people who take anticoagulants or have bleeding disorders. The main clinical test is prothrombin time (how long blood takes to clot), often reported as INR.[1]
Who is more likely to have low intake
- Newborn babies who did not receive vitamin K at birth, because little vitamin K crosses the placenta; newborn vitamin K is standard medical care.[1]
- People with malabsorption conditions, such as cystic fibrosis, celiac disease, ulcerative colitis or short bowel syndrome, or after bariatric surgery.[1]
Potential benefits and quality of evidence
- Vitamin K is essential for normal blood clotting.[1] Established
- Some studies link higher vitamin K intakes to better bone density or fewer hip fractures, but it is unclear whether supplements reduce osteoporosis risk.[1] Limited evidence
- There is not enough trial evidence to say whether vitamin K supplements lower the risk of heart disease.[1] Not enough evidence
Side effects
- No adverse effects from vitamin K in food or supplements have been reported in healthy people.[1]
Risks of too much
- Vitamin K has low potential for toxicity. The main risk is for people taking warfarin or similar medicines, where sudden changes in vitamin K intake can make the medicine work less well or too strongly.[1]
Medicine and supplement interactions
- Warfarin and similar anticoagulants (e.g., acenocoumarol): Vitamin K works against these medicines. Sudden changes in vitamin K intake from food or supplements can change how well they work, so intake should stay consistent and any change should be discussed with the doctor.[1]
- Antibiotics: Can reduce vitamin K made by gut bacteria; some cephalosporins may also block vitamin K action. Usually only relevant with long-term use.[1]
- Bile acid sequestrants (e.g., cholestyramine, colestipol): Can reduce absorption of vitamin K and other fat-soluble vitamins.[1]
- Orlistat: Can reduce absorption of fat-soluble vitamins; combined with warfarin, it might change clotting time significantly.[1]
Never start, stop or change a prescribed medicine because of this list — talk to your doctor or pharmacist.
Pregnancy and breastfeeding
- Needs in pregnancy are the same as for other adult women. Little vitamin K crosses the placenta, which is why newborns are usually given vitamin K at birth.[1]
Kidney and liver cautions
- The liver uses vitamin K to make clotting proteins, so liver disease can affect clotting. People with liver or kidney disease, especially those on blood thinners, should get advice from their doctor before taking vitamin K supplements.[1]
Upper intake limits
The US Food and Nutrition Board did not set a Tolerable Upper Intake Level for vitamin K because of its low potential for toxicity. This does not remove the warfarin interaction risk.[1]
When to talk to a professional
Talk to a doctor or registered dietitian before starting a supplement, especially if you are pregnant or breastfeeding, have a long-term illness, or take any regular medicines.
Do not start, stop or change a prescribed medicine because of anything you read here.
Supplements sold without a prescription are not automatically safe. Doses, quality and interactions still matter.
Seek medical care promptly if you have severe, sudden or worsening symptoms.
If you take warfarin or another blood thinner, do not start vitamin K supplements or make big changes in how many leafy greens you eat without talking to your doctor.
Still being verified
- ICMR-NIN 2020 vitamin K values are not in the brief note and were not verified; not stated.
References
- NIH Office of Dietary Supplements. Vitamin K — Fact Sheet for Health Professionals (opens in a new tab) (2021-03-29). Accessed 9 Oct 2026.
Sources checked: 9 Oct 2026
This page is general education, not personal medical advice. For diagnosis, treatment or medicines, please talk to a qualified doctor, registered dietitian or pharmacist. Read our medical & AI disclaimer.