Myths about the vitamin K shot for newborns are all over social media these days. If you’re about to be a parent, you might have run across claims that vitamin K has a “black box” safety warning or slows babies’ blood flow. Or maybe you have questions about why babies need a shot so soon after birth. We’ll walk you through why vitamin K is essential preventive care for newborns and how we know it’s safe.

What is vitamin K, and why is it important for newborns? 

“Vitamin K helps with blood clotting, and clotting is necessary to prevent bleeding,” says Allison Henry, director of newborn care at Cedars-Sinai Guerin Children’s in Los Angeles.  

Luckily, it’s easy for most of us to get enough vitamin K from food sources. Green vegetables—like collards, spinach, kale, and broccoli—as well as soybeans and their oil are all good sources. On top of that, the bacteria in our colons produce some vitamin K once we start eating solid food.  

The difference with newborns: All babies are born with very little vitamin K stored in their bodies. And breast milk doesn’t have enough to close the gap. That’s why a single shot of vitamin K given shortly after birth is routine. The American Academy of Pediatrics started recommending the injection in 1961. 

The shot works in two ways. Some of the vitamin K immediately goes into a newborn’s bloodstream, so they have what they need in the short term. And some is stored in the liver and is slowly released, ensuring that the baby has enough vitamin K for the first few months of life. 

The shot isn’t a vaccine, Henry points out. “It doesn’t involve the immune system like a vaccine does. It’s simply supplementing a vitamin that’s present in low levels at birth.”  

And if babies don’t get that vitamin, the consequences can be deadly.  

What is vitamin K deficiency bleeding? 

Vitamin K deficiency bleeding (VKDB) occurs when babies can’t stop bleeding because they don’t have enough vitamin K to form blood clots.  

“The problem we worry about the most would be bleeding in the brain,” says Henry, “because there’s no evident bleeding on the outside of the baby’s body. So by the time the family shows up to the clinic, the damage to the baby’s brain has already been done.” 

And that can be devastating. “It can cause neurologic disability and long-term neurodevelopmental disabilities,” says Henry. “And babies can die.” 

When bleeding happens within the first 24 hours after birth, it’s usually because the birth parent has been taking a medicine—like some antibiotics or drugs that treat seizures—that interferes with how the body uses vitamin K. (Small amounts of those medications can pass through the placenta to the baby.) VKDB that occurs in the first week of life affects 1 in 60 to 1 in 250 newborns.  

Infants are at risk for VKDB until they begin eating food other than breast milk or formula at around four to six months. (Baby formula is fortified with vitamin K, but babies may not absorb enough to prevent VKDB, so those who will be formula-fed also need the injection.) 

Most cases of VKDB show up between 24 hours and 1 week after birth. Late-onset VKDB, which typically occurs in babies who are exclusively breastfed and didn’t receive the vitamin K shot, can appear between week 2 and six months. Thankfully, it’s rare, affecting about 1 in 14,000 to 1 in 25,000 infants. But according to the CDC, that’s only because most newborns get the vitamin K shot. One shot of vitamin K within hours of birth almost entirely erases the risk of VKDB.  

Some parents think that their babies don’t need the vitamin K shot because VKDB is so rare, says Henry. But in fact, “the reason most people don’t know anyone whose child has had this type of devastating bleeding is because we’ve had decades of almost universal vitamin K shots. I think it sets parents up to think that this is like a lightning strike kind of possibility when truly, in babies who don’t receive vitamin K, it’s more common than they think.”  

How much more common? Sadly, newborns who don’t receive vitamin K are 81 times more likely to develop VKDB than newborns who get the shot. And when bleeding happens, one out of every five babies will die.  

Vitamin K myths 

In recent years, more parents have been turning down the vitamin K shot for their newborns.  

In a 2026 paper, researchers reviewed medical records for more than five million babies born in the United States between 2017 and 2024. During that time, the percent of newborns who didn’t get the vitamin K injection increased from roughly 3% to 5%. That may be just a couple of percentage points, but it represents tens of thousands more babies born at risk of VKDB every year.  

So why might parents refuse a potentially lifesaving shot for their babies? 

‘Natural is better’ thinking 

Henry points out that some parents are drawn to what they consider “natural” practices, so they might turn down the vitamin K injection because they see it as an unnatural intervention. “But babies used to die of vitamin K deficiency, and that was natural,” she notes.  

Not worth the pain? 

Some parents worry that the injection will be painful for their newborns. “I show them how small the needle is and how quickly the injection is over, and I offer to let the baby breastfeed during the injection as a way to provide comfort,” says Henry. 

Side effects and the vitamin K ‘black box’ warning 

Some parents refuse the vitamin K shot for their newborns because of its “black box” warning. The FDA requires the warning—it’s enclosed in a solid black border—on the packages of some drugs to alert clinicians to potential serious side effects. And injectable vitamin K carries one. Should parents be worried? 

“These boxed warnings are the highest safety warnings the FDA issues, but they are meant to be taken in context,” said Kristan Scott, a physician with the division of neonatology at Children’s Hospital of Philadelphia, in a recent video from the hospital. “This warning exists because adults can have very severe allergic reactions to IV dosing of this vitamin.” (An adult might need IV vitamin K in an emergency to reverse the blood-thinning medicine warfarin, for example.) 

But newborns are given vitamin K as an injection into the thigh muscle, not through an IV. And Scott noted that doctors don’t see the same allergic reaction. “We give a lot of vitamin K to babies, so we have a lot of good data on this.” 

Additives in the vitamin K shot 

Some parents who turn down the injection say they’re worried about what else, besides vitamin K, might be in it. “I never got a vitamin K shot for my babies,” writes one parent on Facebook. “It’s not just a vitamin. It contains a number of additives that are not good.”  

One additive in the vitamin K injection is benzyl alcohol, which is used as a preservative. And there was a time when parents were right to worry about it. In 1982, the FDA received reports that 16 premature babies had died at two hospitals, possibly because the equipment that was used to deliver drugs to them had been flushed regularly with benzyl alcohol. The FDA responded by recommending that the chemical not be used in newborn care.  

But the small amount of benzyl alcohol in the vitamin K injection isn’t dangerous to healthy newborns. Neither are the other preservatives. 

“The preservatives that are used in the vitamin K shot are included in extremely tiny quantities and have been proven to be safe for decades,” says Henry. And many newborns receive a version of the vitamin K shot that doesn’t contain preservatives.  

‘Slow’ blood 

Another common myth is that babies are born with low levels of vitamin K for a reason: Because vitamin K causes clotting, if babies had more of it, their blood would become too thick and would circulate too slowly, leading to clots. But if the injection gave babies so much vitamin K that it impaired their blood flow, we would get reports of that happening. And we don’t.  

Can vitamin K pass from parent to baby? 

“There are natural ways to help vitamin K levels be optimal so that you don’t need a shot,” says one mom on Facebook. “Leave baby’s cord intact until all the blood has gone into their bodies! … For moms who are concerned, I recommend working on your gut health prior to and during pregnancy. Eat vitamin K-rich foods throughout pregnancy and while nursing.”   

That advice sounds sensible, but it won’t prevent VKDB. 

It’s good to eat foods high in vitamin K—and to take prenatal vitamins—but neither will get enough vitamin K into the fetus. “Vitamin K passes from the birth parent to the fetus very poorly,” says Henry. “It just doesn’t cross the placenta well. So the amount of vitamin K that the birth parent consumed during pregnancy does not change the amount of vitamin K that the fetus receives.” 

As for delayed cord clamping, it doesn’t do much because the placental barrier is still in place. 

“Due to the poor transfer of vitamin K from the placenta to the fetus, delayed clamping of the umbilical cord doesn’t actually change the amount of vitamin K that’s going to the baby,” says Henry.  

What about oral vitamin K? 

Some parents wonder whether they can skip the vitamin K injection and instead give their newborn vitamin K drops by mouth. After all, while the FDA hasn’t approved oral vitamin K for newborns in the US, it’s an option elsewhere.  

In the Netherlands, for example, newborns typically get 1 milligram of oral vitamin K drops shortly after birth, then breastfed babies get a daily dose of the vitamin for the next three months. In 2011, that dose increased from 25 micrograms to 150 mcg, giving scientists a chance to see whether the higher dose prevented more cases of bleeding. It did. But the oral drops still didn’t beat the shot, which has come close to eliminating VKDB. (The study authors wrote that “the protection obtained by this six-fold dose increase is limited in comparison with the excellent protection offered by a single dose of [intramuscular] vitamin K after birth.”) 

It’s not clear why the drops weren’t as effective as the shot. Perhaps some parents missed doses, or maybe some babies don’t absorb enough vitamin K when it’s given by mouth, the authors suggested. 

Bottom line 

The vitamin K shot is a routine, safe, and effective way to prevent devastating bleeding and death in newborns.