Vitamin K is a fat-soluble vitamin.
Phylloquinone; K1; Menaquinone; K2; Menadione; K3
Vitamin K is known as the clotting vitamin, because without it blood would not clot. Some studies suggest that it helps maintain strong bones in the older adults.
The best way to get the daily requirement of vitamin K is by eating food sources. Vitamin K is found in the following foods:
- Green leafy vegetables, such as kale, spinach, turnip greens, collards, Swiss chard, mustard greens, parsley, romaine, and green leaf lettuce
- Vegetables such as Brussels sprouts, broccoli, cauliflower, and cabbage
- Fish, liver, meat, eggs, and cereals (contain smaller amounts)
Vitamin K is also made by the bacteria in the lower intestinal tract.
Vitamin K deficiency is very rare. It occurs when the body can't properly absorb the vitamin from the intestinal tract. Vitamin K deficiency can also occur after long-term treatment with antibiotics.
People with vitamin K deficiency are often more likely to have bruising and bleeding.
If you take blood-thinning drugs (such as anticoagulant/antiplatelet drugs), you may need to limit vitamin K foods. You may also need to eat a consistent amount of vitamin K containing foods on a day to day basis if you consume these foods. You should know that vitamin K or foods containing vitamin K can affect how these drugs work.
It is important for you to keep vitamin K levels in your blood about the same from day to day. Ask your health care provider how much vitamin K-containing foods you should eat.
The Recommended Dietary Allowance (RDA) for vitamins reflects how much of each vitamin most people should get each day.
- The RDA for vitamins may be used as goals for each person.
- How much of each vitamin you need depends on your age and gender.
- Other factors, such as pregnancy, breast-feeding, and illness may increase the amount you need.
The Food and Nutrition Board at the Institute of Medicine Recommended Intakes for individuals - Adequate Intakes (AIs) for vitamin K:
- 0 to 6 months: 2.0 micrograms per day (mcg/day)
- 7 to 12 months: 2.5 mcg/day
- 1 to 3 years: 30 mcg/day
- 4 to 8 years: 55 mcg/day
- 9 to 13 years: 60 mcg/day
Adolescents and adults
- Males and females age 14 to 18: 75 mcg/day
- Males and females age 19 and older: 90 mcg/day for females (including those who are pregnant and lactating) and 120 mcg/day for males
Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron Manganese, Molybdenium, Nickel, Silicon, Vanadium, and Zinc. National Academies Press. Washington, DC, 2001. PMID: 25057538 www.ncbi.nlm.nih.gov/pubmed/25057538.
Mason JB. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Schafer AI, eds. Goldman-Cecil Medicine. 25th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 218.
Salwen MJ. Vitamins and trace elements. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 26.
Reviewed By: Emily Wax, RD, The Brooklyn Hospital Center, Brooklyn, NY. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.