Vitamin K shot for newborns: benefits and safety

As you prepare to welcome your baby, it’s natural to have questions about what happens after birth. Your care team is there to support you and help you make informed choices, including simple steps that can help protect your newborn in those first moments. One of those steps is the vitamin K shot, which is given soon after birth and can help reduce the risk of serious bleeding in the first weeks and months of life.

Understanding why vitamin K is recommended can help you feel more confident as you make decisions for your baby.

Why vitamin K matters for newborns

Vitamin K is an essential nutrient that helps the body form blood clots and stop bleeding. Because it’s essential, the body can’t make enough on its own.

Newborns are born with very low levels of vitamin K. Most vitamin K usually comes from food, but human milk contains only small amounts. A smaller portion comes from healthy bacteria in the intestines, which newborns haven’t developed yet.

Because of this, babies — especially those who are breastfed — may have low vitamin K levels for the first several months unless they receive supplementation. 

What can happen when vitamin K levels are low

Low vitamin K can lead to a condition called vitamin K deficiency bleeding, or VKDB. This can cause bleeding without warning or injury.

In some cases, bleeding can occur inside the body, including in the brain. This type of bleeding can be life-threatening and may lead to long-term complications.

There are three types of VKDB:

• Early: Occurs within the first 24 hours after birth and can’t be prevented because it begins before vitamin K can take effect
• Classical: Occurs between day 2 and the first week of life. This is the most common type and is much less likely when a baby receives the vitamin K shot
• Late: Occurs between week 2 and 6 months. This is the most serious type and often involves bleeding in the brain 

Why the vitamin K shot is recommended

VKDB is rare in the United States, largely because most newborns receive the vitamin K shot at birth.

Babies who don’t receive the shot are much more likely to develop severe bleeding compared to those who do. Giving vitamin K shortly after delivery helps reduce this risk during a time when babies are most vulnerable.

How the vitamin K shot works

The vitamin K shot is given as a single injection into a muscle after birth.

This approach allows the body to absorb the full dose. It raises vitamin K levels right away and then releases small amounts over the next two to three months, helping support healthy clotting during early development.

In the United States, there are no FDA-approved oral vitamin K products for newborns. In countries where oral vitamin K is used, rates of late VKDB tend to be higher compared to the shot.

Is the vitamin K shot safe?

Yes. Vitamin K has been used safely for newborns for decades.

Large studies have found no link between the vitamin K shot and cancer. The American Academy of Pediatrics first recommended it in 1961, and it continues to be recognized as a safe and effective way to help prevent dangerous bleeding.

Most vitamin K shots don’t contain preservatives. If a preservative is included, it’s in a very small amount and considered safe. You can ask your care team about preservative-free options.

Why timing matters

The risk of bleeding begins at birth and is highest in the first weeks of life.

Because newborns start with very low vitamin K levels, protection is needed right away. Waiting until a baby is older — such as 2 months — leaves a gap when the risk is highest.

Babies remain at risk until they receive vitamin K or begin eating solid foods and developing more gut bacteria.

Does formula provide enough vitamin K?

Infant formula contains vitamin K. However, newborns don’t absorb enough from formula alone to reliably reduce the risk of bleeding.

The vitamin K shot is still recommended for all newborns, regardless of feeding method. 

Possible side effects

Side effects are usually mild and short-lived. They may include:

• Bruising at the injection site
• Pain at the injection site
• Swelling

Helping your baby stay comfortable

You can help make the experience more soothing for your newborn.

• Feed your baby during or after the shot
• Hold your baby close
• Allow your baby to suck for comfort

These simple steps can help reduce discomfort and support bonding.

According to Jeffrey Silvers, M.D., medical director of pharmacy and infection control at Sutter, “A small jab at birth with a very safe, well-studied vitamin causes insignificant pain to your new baby compared to the suffering that will occur if they develop a bleed from vitamin K deficiency.”

Welcoming a new baby comes with a lot to think about. If you have questions about the vitamin K shot or any part of newborn care, your care team can guide you and talk through your options. You don’t have to navigate these decisions alone.