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If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
Vitamin K is an essential nutrient that your body needs to help your blood clot properly (coagulation) and to maintain the health of your bones (Tsugawa, 2020). It comes in two primary forms: vitamin K1 (phylloquinone) and vitamin K2 (menaquinone). Vitamin K1 comes from leafy greens like spinach, and vitamin K2 comes from some fermented foods as well as from the bacteria in your gut (Halder, 2019). Because we get K1 from food and our bodies naturally make K2, vitamin K deficiency in adults is rare (NIH, 2021).
However, some people with malabsorption issues—when the intestine is unable to absorb enough nutrients—or people taking certain medications may be at risk for vitamin K deficiency. Newborns are a specific subgroup that is at high risk for this deficiency (NIH, 2021).
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Symptoms of vitamin K deficiency
Vitamin K helps coagulation (clotting), a process that prevents excessive bleeding both inside and outside the body. When you don’t have enough vitamin K, your body can’t make enough of the proteins it needs for your blood to clot. Therefore, the primary symptom of severe vitamin K deficiency is easy or excessive bleeding. People with a vitamin K deficiency may also bruise easily, bleed from the gums, and show other manifestations of impaired coagulation (Eden, 2021; Najeeb, 2016).
In infants, signs and symptoms of vitamin K deficiency include bleeding from where the umbilical cord was cut, bleeding from the gastrointestinal tract, nose, or skin, and in severe cases, bleeding in the brain (Araki, 2020).
Vitamin K deficiency causes and risk factors
Most U.S. diets contain an adequate amount of vitamin K, and healthy people without dietary restrictions are not at risk for vitamin K deficiency. Those at risk include newborns, people on specific medications, and people with malabsorption disorders (NIH, 2021).
Vitamin K deficiency in newborns
Newborn babies are specifically at risk for vitamin K deficiency for a few reasons. First, vitamin K does not travel well across the placenta, making the level of vitamin K the baby is getting in utero very low. Second, newborns have an underdeveloped level of gut bacteria. Third, breast milk does not contain very high levels of vitamin K, making newborns who are breastfed more at risk than those who are fed formula.
Therefore, newborns start out with low levels of vitamin K. To prevent vitamin K deficiency in newborns, they are given vitamin K at birth (Araki, 2020; Eden, 2021).
Anticoagulants and other medications
Certain medications interfere with vitamin K levels. For example, warfarin (Coumadin) is an anticoagulant often prescribed for people who are at increased risk for developing harmful blood clots or those who have already had a harmful blood clot. Anticoagulants keep the blood from clotting by disrupting vitamin K’s role in a complex cascade that makes our blood clot.
People on warfarin need to take in a consistent amount of vitamin K, and if they change the amount of vitamin K they are getting, the impact of the medication may change as well. When on warfarin, too little vitamin K can increase your risk of bleeding, and too much vitamin K can decrease warfarin’s anti-clotting ability. When taking warfarin, it’s important to consult a healthcare provider before making dietary changes like increasing your vitamin K intake (NIH, 2021).
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People taking antibiotics are also at risk for vitamin K deficiency because antibiotics can destroy the gut bacteria that make vitamin K. Finally, bile acid sequestrants (medications that lower cholesterol) may interfere with the body’s absorption of vitamin K and their use could lead to a deficiency (NIH, 2021).
People with malabsorption disorders like cystic fibrosis or celiac disease may develop vitamin K deficiency because the intestine is unable to absorb enough nutrients. People who have had bariatric surgery or surgery that shortened their intestines may also be at risk (NIH, 2021).
Diagnosing a vitamin K deficiency
Healthcare providers don’t routinely check for vitamin K deficiency in people without telltale symptoms like bleeding or bruising (NIH, 2021). Before running any blood tests, healthcare providers consider someone’s medical history and any factors that might increase the risk for vitamin K deficiency, such as taking anticoagulants.
One indirect way to check for and diagnose vitamin K deficiency is to look at someone’s prothrombin time (Eden, 2021). Prothrombin is a protein that your blood needs to clot, and it is dependent on vitamin K. Without vitamin K your body can’t make prothrombin and other vital proteins your body needs to have a healthy clotting response (NIH, 2021).
Prothrombin time is the amount of time that it takes for your blood to clot. If you bleed longer than usual without clotting, that may signify to your healthcare provider that your body lacks vitamin K (Eden, 2021).
Vitamin K deficiency treatment
Treating vitamin K deficiency depends on its severity and related symptoms (Eden, 2021).
Adults that have a vitamin K deficiency because of lack of dietary intake may only need a low-dose supplement or a change in diet. For people with malabsorption issues, oral supplements are sometimes not enough, and healthcare providers might need to give vitamin K through an IV (Eden, 2021).
Based on their prothrombin time and bleeding, a healthcare provider might diagnose someone with vitamin K deficiency bleeding (VKDB). In the case of this kind of significant bleeding, a person will likely receive injections or IV infusions of vitamin K. They may also need the blood-related product, fresh frozen plasma (Eden, 2021).
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Treating vitamin K deficiency in newborns
Because infants have a high risk of developing vitamin K deficiency, healthcare providers routinely give newborns vitamin K shortly after birth by injecting it into a muscle (Eden, 2021).
Without these preventative measures, newborns are at risk for vitamin K deficiency bleeding (Araki, 2020).
Daily vitamin K requirements
Even though your body makes some vitamin K, you need to take in some vitamin K from your diet. For women over the age of 19, 90 mcg of vitamin K is an adequate intake of the vitamin. For men over 19, 120 mcg of vitamin K is an adequate intake (NIH, 2021).
You can get vitamin K1 from green leafy vegetables like collards, kale, and spinach. Some fruits like kiwi fruit and blueberries also have vitamin K1 (Halder, 2019).
Vitamin K2 is a little harder to get from dietary sources. Fermented foods sometimes have vitamin K2. For example, Natto is a fermented food that people in Japan eat frequently. Some cheeses, as well as meats like chicken and beef, also contain vitamin K2 (Halder, 2019).
At the end of the day, eating a varied diet that includes leafy green vegetables can help you get the vitamin K you need. If you are on warfarin or other vitamin K “antagonists,” or if you have a malabsorption disorder, talk with your healthcare provider to ensure you are getting enough vitamin K.
- Araki, S., & Shirahata, A. (2020). Vitamin K Deficiency Bleeding in Infancy. Nutrients, 12(3), 780. doi: 10.3390/nu12030780. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7146284/
- Eden, R. E., & Coviello, J. M. (2021). Vitamin K deficiency. [Updated Jul 26, 2021]. In: StatPearls [Internet]. Retrieved on Nov. 4, 2021 from https://www.ncbi.nlm.nih.gov/books/NBK536983/
- Fusaro, M., Mereu, M. C., Aghi, A., Iervasi, G., & Gallieni, M. (2017). Vitamin K and bone. Clinical cases in mineral and bone metabolism : the official journal of the Italian Society of Osteoporosis, Mineral Metabolism, and Skeletal Diseases, 14(2), 200–206. doi: 10.11138/ccmbm/2017.14.1.200. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5726210/
- Halder, M., Petsophonsakul, P., Akbulut, A. C., Pavlic, A., Bohan, F., Anderson, E., et al. (2019). Vitamin K: Double Bonds beyond Coagulation Insights into Differences between Vitamin K1 and K2 in Health and Disease. International Journal of Molecular Sciences, 20(4), 896. doi: 10.3390/ijms20040896. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6413124/
- Imbrescia, K., & Moszczynski, Z. (2021). Vitamin K. [Updated Jul 13, 2021]. In: StatPearls [Internet]. Retrieved on Nov. 4, 2021 from https://www.ncbi.nlm.nih.gov/books/NBK551578/
- Najeeb, S., Zafar, M., Khurshid, Z., Zohaib, S., Almas, K. (2016). The role of nutrition in periodontal health: an update. Nutrients, 8(9), 530. doi: 10.3390/nu8090530. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5037517/
- National Institutes of Health (NIH). (2021). Office of dietary supplements – vitamin K. Retrieved October 24, 2021 from https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/
- Reddy, P., & Jialal, I. (2021). Biochemistry, fat soluble vitamins. [Updated Sep 20, 2021]. In: StatPearls [Internet]. Retrieved on Nov. 4, 2021 from https://www.ncbi.nlm.nih.gov/books/NBK534869/
- Tsugawa, N., & Shiraki, M. (2020). Vitamin K Nutrition and Bone Health. Nutrients, 12(7), 1909. doi: 10.3390/nu12071909. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7399911/
- Zekavat, O., Fathpour, G., Haghpanah, S., Dehghani, S., Zekavat, M., Shakibazad, N. (2017). Acquired vitamin K deficiency as an unusual case of bleeding tendency in adults: a case report of a nonhospitalized student presenting with severe menorrhagia. Case Reports in Obstetrics and Gynecology, 2017. doi: 10.1155/2017/4239148. Retrieved from https://pubmed.ncbi.nlm.nih.gov/28928999/