Vitamin K

Studies in people

• Benefit

  Bone fractures in adults³

  Eating more vitamin K may lower fracture risk, but scientists do not yet know for sure.

• Open question

  Kidney function⁴

  Vitamin K supplements did not clearly improve kidney function, though low vitamin K levels were linked to worse kidneys.

• Benefit

  Bone and blood vessel health⁵

  Vitamin K helps keep calcium in bones and out of blood vessels, which may lower fracture and heart risks.

• Benefit

  Bone strength as we age⁶

  Vitamin K helps switch on a bone protein that pulls calcium into bone, and it may work better alongside vitamin D.

• Open question

  Blood sugar control⁷

  Vitamin K supplements slightly lowered a blood sugar measure in people, but other blood sugar and cholesterol results did not change.

Study type not stated

• Benefit

  Blood vessel health¹⁰

  Vitamin K helps proteins that stop calcium building up in blood vessels, but the best amount to eat is not yet known.

Single cases of misuse or overdose

One person or one incident, such as an accidental overdose or a mistake in a kitchen or factory. They are real, but a single case does not show what happens at normal amounts, so the signal does not count them.

• Bleeding in the brain⁹

  A baby born to a mother with vitamin K deficiency after weight-loss surgery had bleeding in the brain.

How it’s made and used

• Bleeding in newborns²

  Vitamin K in breast milk alone is not enough to protect babies from serious bleeding.

• Newborn blood clotting⁸

  Breast-fed babies who drank less milk in their first days were more likely to have low vitamin K.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.