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What are the signs of vitamin K deficiency?

Bleeding is the classic sign of vitamin K deficiency, and it appears only when the deficiency is severe.

Who is most likely to run low

People with conditions that stop them absorbing fat, such as cystic fibrosis, coeliac disease or ulcerative colitis, may not absorb vitamin K properly.

What this means for you

Vitamin K deficiency is rare in adults, and when it happens it usually has a clear cause rather than a dietary one.

The classic sign is bleeding: bruising easily, bleeding gums, nosebleeds, or cuts that take longer than they should to stop. Those effects appear only in severe deficiency, which is part of why the condition goes unnoticed in its milder form.

Not for everyone. The realistic route to deficiency is a condition that blocks fat absorption, such as cystic fibrosis, coeliac disease, ulcerative colitis or short bowel syndrome. Long courses of antibiotics and severe liver disease can also contribute.

Newborn babies are the other group, which is why vitamin K is given at birth in most countries. That is a medical protocol rather than a nutrition question, and the bleeding it is meant to prevent can be catastrophic.

Unsettled. The evidence under that protocol has a hole in the middle of it. A Cochrane review went looking for randomised trials of vitamin K against no vitamin K in preterm infants and found not one. The single eligible study compared three prophylactic regimens against each other in infants born before 32 weeks. The comparison everybody assumes was made at some point has never been made.

Giving the mother vitamin K during pregnancy is not a way round it. Six older trials covering 21,493 women and their newborns were pooled. The mothers' own blood levels went up. Bleeding in the babies did not go down, with a risk ratio of 1.16 that sits either side of no effect. Those trials were mostly judged at high or unclear risk of bias, so read that as a failure to show a benefit rather than as proof there is none.

If you are deciding about this for your own baby, the conversation belongs with the team looking after them. This page can tell you what the trials contain. It cannot weigh a rare catastrophic bleed against an injection on your behalf.

For everyone else, a portion of leafy greens now and then covers the 90 to 120 micrograms a day the body needs.

Because true deficiency is rare, most people who go looking at vitamin K supplements are hoping to prevent something rather than to correct a shortage. Two trial results set the expectation. A two-year trial of 360 micrograms of K2 a day in 123 dialysis patients did not protect their bones, and pooling 14 trials, vitamin K slowed coronary artery calcium a little in patients who mostly had kidney disease. Neither is a reason to supplement a healthy diet that already contains greens.

There is no shortfall figure for this nutrient, and that is not an oversight

Unsettled. For almost every nutrient on this site we can tell you what share of people fall below the requirement. For vitamin K we cannot, because there is no requirement to fall below. The 120 micrograms is an adequate intake rather than a measured requirement, and the national survey's shortfall table holds no row for vitamin K against any reference value. Median intake is 75.4 micrograms a day, 74.5 for men and 76.6 for women, while the mean is 120.4 and the 95th percentile is 364.2. That spread is driven by whether somebody ate a salad on the day they were asked rather than by how different people are.

The reason runs deeper than a missing survey line. Vitamin K carboxylates a family of proteins. The ones in the liver run blood clotting, and what they need is known, which is why the clotting signs of deficiency are well described and why a doctor can test for them. The proteins outside the liver, involved in bone and in the calcification of arteries, have no agreed target at all. Nobody has established how much vitamin K those need to work properly.

Not for everyone. What follows from that is a narrow claim rather than a broad one. Real vitamin K deficiency, the kind that causes bleeding, is a genuine medical event, it is rare, and it almost always sits alongside something that blocks fat absorption or a newborn who has not yet been given vitamin K. That part is not in doubt and belongs to a clinician. The idea that a large share of ordinary adults are quietly short of vitamin K has no number behind it, because the number does not exist.

Written from the evidence cards and the data on this page, then checked back against the sources. Bioma Learn has no human medical reviewer at this time and we say so rather than invent one. Information, not medical advice. How we verify.

Where to get it from food

All vitamin K sources ranked →

A symptom list is not a diagnosis. Every sign on this page has other causes that are more common than a nutrient deficiency, and the way to know is a blood test rather than a checklist.

Full guide: Vitamin K: the nutrient whose most useful fact is about a medicine

Source. Bleeding and hemorrhage are the classic signs of vitamin K deficiency, although these effects occur only in severe cases. — NIH Office of Dietary Supplements, Vitamin K - Health Professional Fact Sheet, checked 2026-09-16. Evidence level E.

Source. People with malabsorption syndromes and other gastrointestinal disorders, such as cystic fibrosis, celiac disease, ulcerative colitis, and short bowel syndrome, might not absorb vitamin K properly — NIH Office of Dietary Supplements, Vitamin K - Health Professional Fact Sheet, checked 2026-09-16. Evidence level E.