Vitamin K for Newborns
In the first hours after birth, babies in the US are offered a few routine treatments, including the hepatitis B vaccine, eye ointment, and a small shot of vitamin K. Vitamin K has been part of that list since 1961. Lately, more families are asking about it, and some are choosing to skip it.
Good questions deserve good answers. Here's what the research shows, in plain language, so families can make the call that's right for them.
What vitamin K does
Vitamin K is a vitamin. The name comes from the German word for clotting, and that's its main job: it switches on the clotting factors that help blood form a clot and stop bleeding. It also supports bone health.
Adults get most of theirs from food (leafy greens, broccoli, cabbage, avocado, kiwi) and a smaller share from gut bacteria. We don't store much of it, so our bodies rely on a steady supply.
Why babies start out low
Every baby is born with very little vitamin K. That's true for every baby, every type of birth, every family.
Two reasons:
Very little vitamin K crosses the placenta during pregnancy, even when the gestational parent's own levels are healthy.
A newborn's gut doesn't have the bacteria yet to make its own.
Levels dip lowest around days two and three, and don't reach adult range until about six months, when solid foods start.
Human milk is wonderful food, and it happens to be naturally low in this one nutrient. Formula has vitamin K added. That means babies who are fed only human milk (nursed, chestfed, or pumped) depend more on a vitamin K dose after birth. It's simply how this part of human biology works.
What vitamin K deficiency bleeding is
When levels drop too low, a baby's blood can stop clotting well and bleeding can start on its own, with no injury at all. This is called vitamin K deficiency bleeding, or VKDB. It's rare. It's also serious.
There are three types:
Early, in the first 24 hours. Usually linked to certain medications the gestational parent took in pregnancy.
Classic, in the first week, most often days two to three. Bleeding tends to show up at the cord, the nose, the skin, the gut, or a circumcision site.
Late, from about week two through six months, most often weeks three to eight. This is the most dangerous kind, because it often starts with bleeding in the brain.
About one in five babies with late VKDB dies, and many who survive have lasting brain injury. Often there are no warning signs beforehand.
How well the shot works
In European data from before routine vitamin K, somewhere around 4 to 7 of every 100,000 babies developed late VKDB. With the shot, that number falls to between 0 and about 0.4. One large British study found babies who got no vitamin K were 81 times more likely to develop VKDB than babies who got the shot.
For circumcision specifically, a 1960s trial found bleeding afterward in about 14 percent of babies who hadn't had vitamin K, compared with 2.5 percent of those who had. That's why most hospitals ask for it beforehand.
The shot is a single dose into the thigh muscle. The muscle releases it slowly over the following months, which is how one dose protects through the late-bleeding window.
What about oral drops?
Several countries, including Canada, the UK, and the Netherlands, offer an oral option for families who decline the shot. It takes multiple doses over the first weeks, and every dose matters. Babies who missed the last dose make up many of the oral-regimen cases of late bleeding. Even completed oral schedules protect a little less reliably than the shot, especially for babies with an undiagnosed liver or gallbladder condition.
In the US, there's no FDA-approved oral vitamin K for infants. Drops sold as supplements aren't regulated, so the amount in each bottle can vary. That's a big part of why US guidance sticks with the shot.
Questions families often ask
Does a gentle birth mean my baby doesn't need it? Research hasn't found that. In 2013, six babies in Tennessee were hospitalized with late VKDB. All six had uncomplicated vaginal births, all were fed human milk, and all of their families had declined the shot.
Isn't it linked to leukemia? A small British study raised that question in 1990. Researchers spent the next two decades checking, and the largest, most careful studies (published in 2002 and 2003) found no link to leukemia or any childhood cancer.
What about the black box warning? That boxed warning on the label is about rare reactions that have occurred almost entirely in adults getting large IV doses. Health organizations around the world continue to recommend the newborn shot.
I'm worried about the ingredients. Families can ask for the preservative-free version. It's vitamin K plus a few ingredients that help it dissolve and keep the pH right.
Does it cause jaundice? Early versions in the 1940s and 50s used much higher doses and a different formula, and those did cause problems. Today's dose and formula haven't been shown to raise jaundice risk in full-term babies.
Will it hurt? It's a quick pinch. Holding baby skin to skin or nursing during the shot helps, and one study found babies held skin to skin had lower pain scores than babies who were swaddled.
Signs worth a call, for every baby
Rarely, bleeding happens even after the shot, so it's good for every family to know what to watch for:
Sleepiness that's hard to wake from, or trouble feeding
Unusual fussiness
A bulging soft spot
Bruising without a reason, especially on the head or face
Bleeding from the nose, gums, cord, skin, or circumcision site
Paler skin than usual, or pale gums for babies with darker skin
Yellow eyes after three weeks old
Blood in the diaper, black tarry stool after day three, or vomiting blood
Any of these is worth calling the baby's provider right away.
Where this leaves families
More families are choosing to decline the shot. A JAMA study published this month found the share of US babies who didn't receive it rose from 3.1 percent in 2017 to 6.8 percent in 2025.
The worries behind those choices usually come from love: wanting to protect a brand-new baby from anything unnecessary. That's a good instinct. It works best paired with solid information, early, from people families trust.
If you're expecting, talk it through with your pediatrician before the birth. Evidence Based Birth's full Signature Article on vitamin K is a great next read. And bring your questions to us. That's what we're here for.
Sources
Evidence Based Birth, "Evidence on: Vitamin K for Newborns" Signature Article (Dekker & Ailshire, updated Feb 19, 2025): main source for the biology, VKDB types and rates, the 81x figure, oral vs. shot data, the 1961 circumcision trial, the 2013 Tennessee cases, leukemia, boxed warning, ingredients, jaundice, skin-to-skin pain study, and warning signs
ABC News on the JAMA study (Nov 5, 2026): 3.1% to 6.8% of babies not receiving the shot, 2017 to 2025
JAMA, Scott et al. (Nov 2026): the underlying study
