Your baby’s first few hours of life can be filled with lots of new experiences. The medical team will weigh and measure your baby, check their vital signs, examine them from head to toe, and perform other routine newborn care. Depending on the hospital, your baby may also receive antibiotic eye ointment or drops and their first hepatitis B vaccine.
Another routine part of newborn care is a vitamin K shot. But what is vitamin K, and why is this injection recommended for newborns?
Let’s take a closer look at what vitamin K does and why it is an important part of your baby’s care after birth.
Purpose of Vitamin K
Vitamin K is a nutrient that helps the body form blood clots—the body’s natural way of stopping bleeding. It also plays an important role in maintaining healthy bones.
Older children and adults get vitamin K from foods such as leafy green vegetables, meat, dairy products, and eggs. The healthy bacteria that live in our intestines, known as the gut microbiome, also make some vitamin K.
Newborns, however, naturally have very low levels of vitamin K at birth. Because of this, they can be at risk for a rare but potentially serious bleeding condition called vitamin K deficiency bleeding (VKDB).
The good news is that VKDB can be prevented with a single vitamin K shot. The injection is typically given in your baby’s thigh within the first 6 hours after birth.
Because this one-time injection provides important protection during a vulnerable time in a baby’s life, pediatricians have recommended vitamin K shots for newborns since 1961.
Newborns
Why are newborns low in vitamin K?
There are two main reasons newborn babies have such low levels of vitamin K:
1. Not much vitamin K crosses the placenta.
During pregnancy, many nutrients pass from the mother to the developing baby through the placenta. Vitamin K, however, does not cross the placenta very easily, so babies are born with only small amounts stored in their bodies.
2. Their gut bacteria are still developing.
The healthy bacteria that live in our intestines help make vitamin K. Newborns have not yet developed the same gut microbiome as older children and adults, so their bodies cannot produce enough vitamin K on their own.
Vitamin K Deficiency Bleeding
What is vitamin K deficiency bleeding?
When a newborn does not receive vitamin K and has very low levels of the nutrient, they can develop a condition called vitamin K deficiency bleeding (VKDB). Without enough vitamin K, the blood may not be able to form clots properly, making it difficult for the body to stop bleeding.
Bleeding can occur on the outside of the body, but it can also happen internally—where parents may not be able to see it. In some cases, a baby may bleed into the intestines or the brain before there are obvious signs that something is wrong. Bleeding in the brain occurs in about half of babies who develop VKDB and can cause permanent brain injury or even death.
The three types of VKDB
Early-onset VKDB occurs during the first 24 hours after birth. It is usually associated with certain medications taken by the mother during pregnancy that interfere with vitamin K.
Classical VKDB typically occurs between 2 days and 1 week of age. In many cases, doctors do not know exactly why it develops. Early-onset and classical VKDB together occur in approximately 1 in 60 to 1 in 250 newborns.
Late-onset VKDB occurs between 1 week and 6 months of age. It is less common, affecting approximately 1 in 14,000 to 1 in 25,000 babies. However, babies who do not receive a vitamin K shot at birth are about 81 times more likely to develop late-onset VKDB than babies who receive the shot.
Although VKDB is rare, it can have serious consequences. Some cases may be difficult to recognize until significant bleeding has already occurred. As more families choose to decline the vitamin K shot, healthcare providers continue to emphasize the importance of understanding both the risks of VKDB and the protection provided by vitamin K at birth.
Safety
Is the vitamin K shot safe?
Yes. The vitamin K shot has been studied extensively and is considered very safe for newborns.
After the injection, vitamin K is stored in your baby’s liver and released gradually over time. This helps provide the vitamin K your baby needs during the first several months of life—until they are older, eating vitamin K-rich foods, and their bodies are better able to produce vitamin K on their own.
Some parents may have heard about a study published in the 1990s that raised concerns about a possible connection between the vitamin K shot and childhood cancer. These concerns were taken seriously by both parents and the medical community.
Since then, researchers have conducted many additional studies to investigate whether this connection exists. None of the follow-up studies have found evidence that the vitamin K shot causes childhood cancer.
Oral Route
What about oral vitamin K?
Some parents may wonder whether their baby can take vitamin K by mouth instead of receiving the injection. While oral vitamin K is available in some places, newborns do not absorb it as reliably as vitamin K given by injection.
Because the vitamin K shot provides more dependable protection against vitamin K deficiency bleeding (VKDB), it is the recommended option for newborns. A single injection provides the most reliable protection during the first months of life, when babies are especially vulnerable to VKDB.
Breastfeeding
What about breast milk and vitamin K?
Breast milk contains a small amount of vitamin K, but not enough to provide the protection newborns need against vitamin K deficiency bleeding (VKDB). This is one reason breastfed babies who do not receive vitamin K at birth may be at higher risk for VKDB.
As babies grow, their vitamin K needs and sources begin to change. When they are ready to start eating solid foods—usually around 6 months of age—they can begin getting vitamin K from their diet. As their gut microbiome also develops, the healthy bacteria in their intestines contribute to vitamin K production as well.
The vitamin K shot at birth helps bridge this early period, when newborns have limited vitamin K stores and are not yet getting much vitamin K from food or their developing gut microbiome.
Symptoms of VKDB
What are the warning signs of VKDB?
One of the challenges with vitamin K deficiency bleeding (VKDB) is that there may not be any obvious warning signs before serious bleeding occurs. In some cases, a baby may appear well until bleeding has already begun.
Signs of VKDB can include:
- Bleeding from the umbilical cord or nose
- Skin that looks unusually pale—or pale gums in babies with darker skin tones
- Bruising easily, especially around the head or face
- Blood in the stool or stool that is black, dark, or sticky
- Vomiting blood
- Yellowing of the whites of the eyes that develops 3 weeks or more after birth
- Seizures
- Unusual irritability
- Repeated or excessive vomiting
- Sleeping much more than usual or being difficult to wake
If your newborn or young infant has any of these symptoms, seek medical care right away. VKDB can cause serious internal bleeding, so prompt evaluation is important.
Bottom Line
The first days and months of your baby’s life are a time of rapid growth and development. During this time, newborns naturally have very low levels of vitamin K, which can put them at risk for a rare but potentially life-threatening condition called vitamin K deficiency bleeding (VKDB).
The good news is that this risk can be significantly reduced with a single vitamin K shot given shortly after birth. The shot has been recommended for newborns for decades and has been extensively studied for safety.
As a parent, it’s completely normal to have questions about the medications, treatments, and preventive care recommended for your baby. If you have concerns about the vitamin K shot or want to learn more about its benefits and risks, talk with your baby’s pediatrician. Your healthcare team is here to provide accurate information and help you make informed decisions about your baby’s care.
A single vitamin K shot can provide important protection during a time when your newborn is especially vulnerable—helping give your baby a safer start to life.