All About Giving Newborns the Vitamin K Shot at Birth

If you are giving birth in a hospital, your medical provider may have told you to expect frequent visits and interruptions from doctors, nurses, and lactation consultants. Doctors will assess your baby for respiratory status, height, weight, and vital signs. When they take your newborn for these routine tests and procedures in the first few hours, you may wonder what is mandatory and what is the purpose of each. One of these standard procedures is the vitamin K shot at birth.

Vitamin K is a fat-soluble vitamin, meaning the body’s fat and liver store it. This means it stays in the body longer than water-soluble vitamins, which are easily excreted through urine. However, vitamin K breaks down relatively quickly inside the body and can be expelled through urine and feces, which prevents overdose or vitamin K toxicity. The American Academy of Pediatrics and the CDC recommend all newborns get the shot, which is most effective when administered within six hours after birth.^1,2,3

What Does Vitamin K Do?

Vitamin K helps make up prothrombin, a protein that aids blood clotting. Blood clotting helps prevent excessive bleeding or hemorrhage. Vitamin K is also a significant component of osteocalcin, another protein that helps build healthy bones.²

What is the Vitamin K Shot?

The vitamin K shot is a one-time dose administered intramuscularly into a newborn’s thigh. In a full-term infant, the standard amount is 1 mg. Preterm or particularly small newborns may receive a smaller dose based on the baby’s weight and gestational age.³

The vitamin K shot at birth is not a vaccine. Although it is an injection administered into a muscle, similar to many vaccines, it does not trigger the baby’s immune system.⁴

Ingredients in the shot are:^1,5

• Vitamin K (also called phytonadione)
• Polyoxyethylated fatty acid derivative. This is an emulsifier that keeps vitamin K evenly mixed as a liquid. This ingredient can cause a rare allergic reaction in adults but not babies since they are not sensitized to allergens yet.
• Hydrochloride. This balances the pH of the solution so it is not too acidic or too alkaline. This can prevent it from burning or stinging upon injection.
• Dextrose (also known as sugar)
• Benzyl alcohol. A small amount of preservative to prevent bacterial growth. You would have to give one hundred times this dose of alcohol daily to be toxic to a newborn, and babies only receive one shot.

How Does the Shot Work?

The infant’s bloodstream immediately absorbs the vitamin K upon administering the shot, providing them a quick initial dose of this essential nutrient to prevent bleeding in the first few days of life. The liver stores the rest of the vitamin for the next 2-3 months. It is slowly released over time until the infant’s diet takes over.¹

Side Effects and Risks

The vitamin K shot is safe, but minor risks include:¹

• Injection site reaction with pain, bruising, or swelling
• Scarring of the skin at the injection site
• Allergic reaction to one of the other ingredients in the shot. There has only been one known allergic reaction to the vitamin K shot.

One British study in the 1990s linked the vitamin K shot to an increased risk of leukemia, but multiple repeat studies did not support this finding.⁶

Is the Shot Mandatory?

The shot is not mandatory. The American Academy of Pediatrics has recommended and encouraged it for newborns since 1961, but it is not required.⁷ Unless you explicitly refuse the shot, it is routinely given if you give birth in the hospital. You likely will not be asked to sign a consent form for it, but if you decide to opt out of the shot for your baby, you may need to sign a form stating you understand the risks of forgoing this intervention.⁸

What is Vitamin K Deficiency in a Newborn?

Nearly all newborns are born with low levels of vitamin K because it does not readily cross the placenta while the baby is in the womb. This means increasing the mother’s dietary or supplemental intake of vitamin K during pregnancy will not raise the baby’s vitamin K levels. Newborns’ intestines have also not yet been colonized with good bacteria, meaning there is no synthesizing of vitamin K.⁹

Because a newborn’s diet consists only of breast milk or formula, they do not consume the variety of foods that provide them with this nutrient. Breastfed babies may be particularly deficient in vitamin K because breastmilk contains minimal vitamin K.¹⁰

Since vitamin K is essential to blood clotting, low vitamin K levels can contribute to vitamin K deficiency bleeding in infants. This condition occurs when babies up to six months experience significant bleeding, either inside or outside their bodies. If the bleeding occurs inside an infant’s body, it often bleeds into the brain or gut, going unnoticed until severe. Internal bleeding can cause death in 20 percent of cases. In cases where the infant survives, adverse effects of the bleeding may persist. For example, brain bleeding can cause neurological damage and developmental and motor issues.⁹

Sources of Vitamin K

Children and adults can consume vitamin K through diet. We get vitamin K through green, leafy vegetables, fermented foods, and animal products like meat, dairy, and eggs. Good bacteria also produce vitamin K in the gut.^1,2

Alternatives to the Shot

While maternal diet and nutrition during pregnancy and breastfeeding are essential, maternal supplementation of vitamin K is not typically sufficient to increase a baby’s vitamin K levels through breast milk. This is because vitamin K does not cross readily into breast milk, even at high maternal doses.¹

In parts of Europe and Canada, parents can opt for oral administration of vitamin K instead of the shot. This requires multiple doses at different points of the infant’s first months. There is no licensed oral infant dose of vitamin K in the United States, though some people elect to administer the shot’s contents orally. Still, this is not recommended or approved.⁵

The CDC does not recommend an oral dose of vitamin K as an alternative to the shot because newborns do not consistently absorb vitamin K through the stomach and intestines. The intramuscular shot is much more easily absorbed.¹⁰ Because the oral route of administration requires multiple doses, compliance for completing the series is much worse.¹¹

You can be easily overwhelmed by decisions in the hospital with your newborn. You may hear tons of information and interventions after delivery. But researching these decisions can help prevent you from feeling overwhelmed and decide early about the vitamin K shot at birth for your baby.