Vitamin K is a fat-soluble vitamin that plays a critical role in helping your blood to clot and in supporting healthy bones and blood vessels. When your body doesn’t have enough vitamin K, it can’t properly activate certain clotting factors in the liver, which may lead to an increased risk of bleeding or bruising. In newborns, this can result in a condition known as vitamin K deficiency bleeding (VKDB), which can be very serious without prompt treatment.
Although outright vitamin K deficiency is relatively rare in healthy adults, some people are at higher risk. These include those with malabsorption problems (such as digestive disease, certain surgeries, or liver-/bile-related conditions), long-term use of antibiotics or medications that interfere with vitamin K metabolism, and newborn infants whose stores of vitamin K are very low at birth. Common signs to watch for include easy or excessive bleeding, bruising with little or no injury, nose-bleeds, or in more serious cases, internal bleeding.
Beyond bleeding, vitamin K also helps with bone mineralisation and may influence cardiovascular health (for example by helping prevent calcification of blood vessels). Because of this, a deficiency might contribute indirectly to weaker bones (osteoporosis) and possibly higher cardiovascular risk. On average, adults are advised to consume about 120 micrograms per day for men and 90 micrograms per day for women to maintain healthy levels.
The good news is that vitamin K deficiency can often be prevented with a balanced diet that includes green leafy vegetables, vegetable oils, some dairy and fermented foods, alongside addressing any underlying health issues that interfere with absorption. If there are signs of deficiency or unexplained bleeding, a healthcare provider can assess clotting factors and may recommend vitamin K supplementation.
Reference
- Eden RE, Daley SF, Coviello JM. Vitamin K Deficiency. [Updated 2023 Sep 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK536983/
Serra Húnter Fellow of Sociology at Universitat Rovira i Virgili.
Former DAAD-Gastprofessorin at Julius-Maximilians-Universität Würzburg