Vitamin K is a fat-soluble vitamin. Fat-soluble vitamins are stored in the body in the liver and fatty tissues. Unlike the other fat-soluble vitamins, the body actually stores very little vitamin K. This makes regular dietary intake important. Bacteria in the large intestines help by making a range of vitamin K forms called menaquinones. Vitamin K is also produced by plants (phylloquinone) and is primarily found in green vegetables, brussels sprouts, cabbage, and plant oils. The man-made vitamin K found in supplements is called menadione.
Vitamin K’s functions include:
- Playing an essential role in the blood-clotting process by making the proteins that stop bleeding
- Helping your body make other proteins essential for blood, bones, and kidneys
Adequate Intake (AI)
Vitamin K Deficiency
If you do not get enough vitamin K, your blood will not clot normally. Among healthy people, a deficiency is rare. Symptoms of vitamin K deficiency include:
- Easy bruising and bleeding—nosebleeds, bleeding gums, blood in the urine, blood in the stool, or extremely heavy menstrual bleeding
- Bleeding in the skull in infants
Vitamin K Toxicity
As a fat-soluble vitamin, vitamin K is stored in the body in small amounts. No tolerable upper intake level (UL)—that is, the highest amount healthy people can consume without endangering their health—has been established for vitamin K. However, excess amounts can cause the breakdown of red blood cells and liver damage. To be safe, you should follow the intake guidelines based on your age and gender
Major Food Sources
Foods that are high in vitamin K include:
- Brussels sprouts
- Collard greens
- Bib lettuce
- Green pepper
- Canola and soybean oils
If You Take a Blood-thinning Drug
If you take a blood-thinning drug (anticoagulant), try to consume the recommended intake of vitamin K. Avoid exceeding this. Taking a vitamin K supplement can change the effectiveness of the drug. Talk to your doctor about your how much vitamin K is safe for you.
If You Take Antibiotics
In addition to killing harmful bacteria, antibiotics also destroy the healthful bacteria that live in the intestines and produce vitamin K. You may need to add more foods rich in vitamin K to your diet. Ask your doctor.
If You Have Liver Disease
The liver plays an important role in metabolism and storage of vitamin K. If you have severe liver disease, you may need to take a vitamin K supplement to avoid complications.
If You Have a Newborn Baby
Because vitamin K deficiency can be life-threatening in infants, the American Academy of Pediatrics recommends that all newborns receive an injection of phylloquinone, a plant-based vitamin K. This is the standard of care in most hospitals.
Tips For Increasing Your Vitamin K Intake
- Slice an avocado. Add a little balsamic vinegar and pepper, and scoop out for a snack. Or, mash the avocado and mix with chopped tomatoes and red onions for a refreshing salsa.
- Pack a kiwi and spoon in your lunch for an afternoon snack. The insides of the kiwi can be scooped out and eaten from this natural and easy container.
- Steam ½ cup broccoli or Brussels sprouts, add lemon juice (1 tbsp), pre-chopped garlic (1 tsp), and Dijon mustard (1 tbsp). Or add broccoli to your favorite lasagna or hot dish.
- Mix 2 (10-ounce) packages of frozen chopped spinach, thawed, well drained, 1 8-ounce package of softened low-fat cream cheese, ¼ cup milk, and 1 teaspoon lemon pepper until well-blended. Spoon into a 1-quart casserole dish and sprinkle with 1/3 cup crushed crackers or seasoned croutons. Bake at 350°F (177ºC) until thoroughly heated (about 25-30 min.).
Abbreviations: mcg = microgram; tbsp = tablespoon; tsp = teaspoon
Academy of Nutrition and Dietetics
Choose My Plate—US Department of Agriculture
Dietitians of Canada
Booth SL, Sadowski JA, Pennington JAT. Phylloquinone (vitamin K1) content of foods in the US Food and Drug Administration’s total diet study. J Agric Food Chem. 1995; 43:1574-1579.
Common foods and their vitamin K content. Anticoagulation Europe website. Available at: http://www.anticoagulationeurope.org/files/files/Some%20common%20foods%20and%20the%20vitamin%20K%20content%20Jan%202013%20(1).pdf. Accessed January 25, 2016.
Fat-soluable vitamins: A, D, E, and K. Colorado State University website. Available at: http://extension.colostate.edu/topic-areas/nutrition-food-safety-health/fat-soluble-vitamins-a-d-e-and-k-9-315/. Updated November 2012. Accessed January 25, 2016.
Phytonadione. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated January 18, 2013. Accessed January 25, 2016.
Vitamin K. EBSCO Natural and Alternative Treatments website. Available at: http://www.ebscohost.com/academic/natural-alternative-treatments. Updated September 18, 2014. Accessed Januarty 25 ,2016.
Vitamin K. The Linus Pauling Institute website. Available at: http://lpi.oregonstate.edu/mic/vitamins/vitamin-K. Accessed January 25, 2016.
Last reviewed January 2016 by Michael Woods, MD Last Updated: 3/10/2014