Vitamin K is a fat-soluble vitamin that the body needs for blood clotting and healthy bones. It has two families: Vitamin K1 (phylloquinone) and Vitamin K2 (menaquinone).
Phylloquinone, K1 is produced by plants and comes mostly from leafy greens whereas the menaquinones, K2 is made by bacteria and turns up in fermented food and animal products. Menaquinones are named by the length of their side chain i.e. MK-4, MK-7, MK-9. That chain decides how long the vitamin circulates and which tissues it reaches.
Vitamin K helps an enzyme switch on certain proteins by adding a calcium-binding group to them. The best known are the clotting factors in the liver, which is why its shortage causes bleeding. Apart from this, there are two other proteins known as Osteocalcin and Matrix Gla Protein (MGP) which helps in calcium regulation. Osteocalcin binds calcium into bone while MGP keeps calcium out of the arterial walls. When vitamin K runs short the liver is served first, so clotting can look normal while bone and artery proteins go partly un-activated.
Vitamin K In Different Life Stages
- Infancy: Babies are born with very little vitamin K. Only small amounts cross the placenta, and the gut bacteria that produce menaquinones are not established yet. Breast milk is low in vitamin K, so exclusively breastfed babies carry the highest risk. Most of the baby formulas are fortified. Without prevention this can cause vitamin K deficiency bleeding (though not in every case). The late form appears between one week and six months, and 30% to 60% of those cases involve bleeding inside the skull (CDC, 2024).
- The American Academy of Pediatrics recommends a single intramuscular dose of vitamin K1 at birth (Hand et al., 2022). An over-the-counter K2 supplement is not a substitute.
- Childhood: Children need vitamin K for the bones they are actively building. Adequate intake rises with age. 30 µg a day at 1 to 3 years, 55 µg at 4 to 8 years, 60 µg at 9 to 13 (National Institutes of Health, n.d.). One trial found 45 µg of MK-7 daily for eight weeks improved osteocalcin activation in 55 healthy prepubertal children (van Summeren et al., 2009).
- Adolescence: Teenagers build bone faster than at any point since infancy, and adequate intake rises to 75 µg a day at 14 to 18. Diets on greens tend to fall short, so food is the sensible route here.
- Adulthood: Adult adequate intake is 120 µg a day for men, 90 µg for women. Adult trials have used MK-7 between 90 µg and 360 µg daily; three years of 180 µg slowed bone mineral density loss in postmenopausal women (Knapen et al., 2013).
- Pregnancy: Adequate intake stays at 90 µg a day. Very little vitamin K crosses the placenta, which is part of why babies are born with low stores, and taking more in pregnancy does not reliably change that. High-dose K2 has little trial evidence in pregnancy, so raise it with an obstetrician first.
- Lactation: Adequate intake is again 90 µg a day. Breast milk is naturally low in vitamin K, and maternal supplements are not an accepted replacement for newborn prophylaxis. A mother eating well covers her own needs; the infant’s protection comes from the birth dose.
- Older adults: Appetite, dairy intake and fat absorption all tend to fall with age, and bone loss accelerates after menopause. In Japan, MK-4 at 45 mg daily is a prescription osteoporosis treatment, with a two-year trial reporting sustained lumbar bone density and fewer fractures (Shiraki et al., 2000).
How Much Vitamin K Do We Need?
Those figures are Adequate Intakes (AI), not Recommended Dietary Allowances. An AI (Adequate Intake) gets set when the evidence is too thin for a firm RDA.
They also cover total vitamin K. There is no separate official recommendation for K2, and the values were built mainly around phylloquinone (National Institutes of Health, n.d.). So, supplement doses do not line up with them. A 180µg MK-7 capsule is not “twice the RDA,” it is a different purpose. Age alone does not set the right dose.
The two forms of the vitamin K2, MK-4 and MK-7, are dosed hundreds of times apart because of how long each one lasts. MK-4 clears from the blood within hours, so the Japanese prescription version uses 45 µg a day (Shiraki et al., 2000). MK-7 stays in circulation for days and reaches tissue beyond the liver, so microgram amounts are enough. MK-4 listed at microgram level does not match how that molecule behaves.
Sources of Vitamin K2
Natto, a traditional fermented soybean food, leads by a wide margin at roughly 850 µg of MK-7 per 3-ounce serving. Cheese, other fermented foods and animal products contribute far less; cheddar sits near 4 µg per 1.5 ounces as MK-4 (National Institutes of Health, n.d.). Cheese content varies with the bacterial strains used.
Safety and Drug Interaction
Some people fall short whatever be their age, especially those who are on a very restricted diets, people with fat malabsorption or inflammatory bowel disease, anyone who has had bowel surgery, and people on medications that interfere with vitamin K.
Warfarin is the exception. Vitamin K works directly against it, and the advice is to keep intake steady rather than avoid it, because sudden changes move the drug’s effect either way. Always consult the doctor/prescriber about it.
Where TerraQuino Fits
TerraQuino supplies vitamin K2-7 (MK-7) as an ingredient, produced by a controlled fermentation process, supplied allergen-free, and used in tablets, capsules, soft gels, sachets and liquids.
For brands developing supplements, TerraQuino offers flexibility in creating combined-nutrient products. Vitamin K2-7 can be paired with ingredients such as Vitamin D3, calcium salts, omega-3s, probiotics, Vitamins C and E, and zinc, making it easier for product developers to create well-rounded formulations. Its standardized processes are also designed to support consistent quality and stability from batch to batch.
Frequently Asked Questions
Does the newborn vitamin K injection contain K2?
No. It uses vitamin K1 as a single intramuscular dose at birth.
Is there an official K2 dosage by age?
No. Adequate intake covers total vitamin K and they are based mainly on K1. Supplement doses come from clinical trials instead.
References
Centers for Disease Control and Prevention. (2024). Vitamin K deficiency bleeding: Fact sheet for healthcare providers. https://www.cdc.gov/vitamin-k-deficiency/hcp/fact-sheet/index.html
Hand, I., Noble, L., Abrams, S. A., & American Academy of Pediatrics Committee on Fetus and Newborn, Section on Breastfeeding, and Committee on Nutrition. (2022). Vitamin K and the newborn infant. Pediatrics, 149(3), Article e2021056036. https://publications.aap.org/pediatrics/article/149/3/e2021056036/184866/Vitamin-K-and-the-Newborn-Infant
Knapen, M. H. J., Drummen, N. E., Smit, E., Vermeer, C., & Theuwissen, E. (2013). Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporosis International, 24(9), 2499–2507. https://doi.org/10.1007/s00198-013-2325-6
National Institutes of Health, Office of Dietary Supplements. (n.d.). Vitamin K: Fact sheet for health professionals. Retrieved September 23, 2026, from https://ods.od.nih.gov/factsheets/VitaminK-HealthProfessional/
Ren, R., Liu, J., Cheng, G., & Tan, J. (2021). Vitamin K2 (menaquinone-7) supplementation does not affect vitamin K-dependent coagulation factors activity in healthy individuals. Medicine, 100(23), Article e26221. https://doi.org/10.1097/MD.0000000000026221
Schurgers, L., Teunissen, K., Hamulyák, K., Knapen, M., Vik, H., & Vermeer, C. (2007). Vitamin K-containing dietary supplements: Comparison of synthetic vitamin K1 and natto-derived menaquinone-7. Blood, 109(8), 3279–3283. https://doi.org/10.1182/blood-2006-08-040709
Shiraki, M., Shiraki, Y., Aoki, C., & Miura, M. (2000). Vitamin K2 (menatetrenone) effectively prevents fractures and sustains lumbar bone mineral density in osteoporosis. Journal of Bone and Mineral Research, 15(3), 515–521. https://doi.org/10.1359/jbmr.2000.15.3.515
van Summeren, M. J. H., Braam, L. A. J. L. M., Lilien, M. R., Schurgers, L. J., Kuis, W., & Vermeer, C. (2009). The effect of menaquinone-7 (vitamin K2) supplementation on osteocalcin carboxylation in healthy prepubertal children. British Journal of Nutrition, 102(8), 1171–1178. https://www.cambridge.org/core/journals/british-journal-of-nutrition/article/effect-of-menaquinone7-vitamin-k2-supplementation-on-osteocalcin-carboxylation-in-healthy-prepubertal-children/1819D1C95F6EE0E5F02E919EA7C1B1CF
