Who is at risk of vitamin K deficiency?

Deficiency is very rare in healthy adults. With a varied diet, it is almost impossible to eat so little vitamin K that blood clotting changes.^[1] US adults get 122 to 138 µg a day from food on average.^[1]

The groups at risk are:

• newborn babies who did not get vitamin K at birth: little crosses the placenta, and breast milk contains little^[1]
• people with cystic fibrosis, celiac disease, ulcerative colitis or short bowel syndrome, who may not absorb it well^[1]
• people after bariatric surgery^[1]
• people who take medicines that block vitamin K or lower its absorption^[1]

The main sign of deficiency is bleeding, because blood takes longer to clot.^[1]