Your first memory of taking vitamins may involve Flintstones chewables. But if you were born after 1961, chances are a doctor gave you vitamin K shortly after you entered the world. For decades, doctors have recommended vitamin K shots for all newborns to prevent dangerous internal bleeding in the first six months of life.
Despite its enduring recommendation, data shows more parents refusing the shot for their babies in recent years as vitamin K myths gain traction. We spoke to pediatricians to get the facts about the nutrient, its safety and potential alternatives.
Why is the vitamin K shot recommended?
Vitamin K’s blood clotting properties help stop internal and external bleeding. Adults get vitamin K from leafy green vegetables and microbes in their guts.
Babies are born with very little of this vitamin. That’s because the vitamin doesn’t easily pass through the placenta from mother to baby as other nutrients do. There’s little a mother can do before the baby is born to change that: Eating a vitamin K-rich diet or taking supplements during pregnancy doesn’t appear to improve outcomes.
Low vitamin K puts babies at risk for potentially fatal internal bleeding called vitamin K deficiency bleeding or VKDB. Since the 1960sthe American Academy of Pediatrics has recommended babies get an intramuscular injection of vitamin K shortly after birth to prevent it.
The AAP currently recommends giving the shot within the first six hours of life for babies weighing at least 3.3 pounds.
It works remarkably well.
Research shows an early dose of vitamin K is sufficient protection until a child starts eating solid food around four to six months and can absorb the vitamin themselves.
How do we know the shot is safe?
Doctors have been giving this shot to newborns for over 65 years. An abundance of research during that time has shown the shot is safe and that babies tolerate it well.
Still, here are some common myths you might have heard about it:
Myth: Vitamin K causes jaundice.
Reality: Jaundice in infants, which presents as yellowing skin, is a common and usually mild condition caused by an underdeveloped liver. Vitamin K was linked to jaundice in the 1950s when doctors gave much higher doses (up to 30 mg). Today, doctors give a much lower dose (1 mg) and don’t see this effect in full-term babies. Premature babies are more vulnerable to jaundice and so are given an even lower dose.
Myth: Vitamin K is linked with leukemia.
Reality: A study in 1990 found an association between the vitamin K shot and childhood cancer, but numerous follow-up studies have failed to replicate those results or verify the association. The consensus among medical experts is that there is no association between the vitamin and leukemia.
Myth: Vitamin K’s “black box warning” means the shot is dangerous.
Reality: Vitamin K shots come with an FDA safety warning about the possibility of the patient experiencing a severe allergic reaction. But the boxed message was added because of allergic reactions some adult patients experienced when the vitamin was given to them through an IV. Only a single case of an allergic reaction in an infant has ever been reportedaccording to the U.S. Centers for Disease Control and Prevention.
Myth: The ingredients in the vitamin K shot are toxic.
Reality: The main ingredient in the shot is the vitamin itself. Other ingredients are included to help balance the pH or allow the vitamin to dissolve into a liquid. Some formulations contain a preservative called benzyl alcohol, which can be toxic in larger quantities, but not from the tiny amount in the shot. Many doctors offer a preservative-free option, and the FDA recommends that for infants.
When making any medical decision for you or your child, it is important to weigh the risks and benefits with a doctor.
“In my own experience at Yale for over a decade, I have never witnessed an adverse outcome from the injection,” said Dr. Jaspreet Loyal, a pediatrics professor at the Yale School of Medicine.
How common is vitamin K deficiency bleeding?
If a healthy baby gets the shot, the risk of VKDB is basically zero.
Among those who don’t get the shot, vitamin K deficiency bleeding is somewhat rare, but it can happen spontaneously and lead to tragic outcomes.
Medical experts differentiate the types of vitamin K deficiency bleeding cases by how soon they happen after birth.
Early-onset occurs in the newborn’s first 24 hours and is usually related to medications that the mother is taking — some seizure and tuberculosis medications, for example. The condition can be severe, but doctors monitoring a mother’s medications can avoid this risk by administering vitamin K soon after birth.
Classic vitamin K deficiency bleeding occurs two days to a week after birth. It can involve bruising, bleeding near the umbilical cord, or the site of circumcision.
These first two types are more common and less severe, collectively affecting between 0.4% and 1.7% of newborns who do not get the shot, according to the CDC.
Late vitamin K deficiency bleeding is rarer, but also the most dangerous. It occurs one week to six months after birth. Somewhere between 30% and 60% of all cases involve bleeding in the brain, which can cause permanent damage or death.
It’s hard to know exactly how many babies in the U.S. are at risk of late-onset VKDB. There is no nationwide tracking of vitamin K deficiency bleeding cases, and more severe outcomes might be coded as something else, like a brain hemorrhage or a stroke. Data from European countries in the 1980s put the rate between 4.4 and 7.2 per 100,000 babies who did not get the shot.
If caught early enough, from signs like bruising, bloody stool, pale skin, nose bleeding or lethargy, the condition can be reversible, said Dr. Anna Morad, a pediatrician at Vanderbilt Children’s Hospital. But more severe types of VKDB bleeding can have no warning signs and be difficult to diagnose until it is too late.
Can babies get vitamin K through formula?
Although breastmilk has numerous advantages for babies, it is naturally low in vitamin K. Formula-fed babies are better off when it comes to vitamin K uptake because infant formula contains high levels of the nutrient.
Babies who are primarily or exclusively breastfed are at greater risk if they don’t get the shot.
What about oral vitamin K?
There are no FDA-approved oral vitamin K options in the U.S., which means the only vitamin K you can buy is supplement grade and not regulated or standardized.
Some countries offer an approved oral vitamin K option for newborns, but evidence shows it isn’t as effective as the intramuscular shot.
It requires repeat doses, which can get missed, and there is also not a single agreed-upon dosing schedule, making it confusing for parents and doctors, Loyal said.
