What Is The Vitamin K Shot For Babies?

newborn in hospital. Fresh Meat Media LLC/Getty Images

Before your baby is even minutes old, he or she will get his/her first ever shot.

It might happen so quickly that you don't even notice it, but at the skillful hands of your baby's nurse, your baby will get a shot of Vitamin K in one of his/her thigh muscles.

Vitamin K is injected into newborn babies for one simple reason to help prevent injury and even death from bleeding. Because Vitamin K is a necessary component of blood clotting and because newborns are prone to Vitamin K deficiencies, doctors discovered that by injecting Vitamin K directly into newborns, they could prevent injuries and death by helping the blood to clot.

Vitamin K is a key component in blood coagulation, or blood clotting; without it, newborns' blood does not clot and they could bleed to death or develop other complications from bleeding. 

Why newborns lack Vitamin K

My first thought about the lack of Vitamin K, of course, is why? Obviously nature knows what it's doing in most cases, so why would all babies have lower levels of Vitamin K to begin with? One study found that although babies blood levels of Vitamin K are similar to adults ratio-wise, newborns are still prone to Vitamin K deficiencies since they rely heavily on breast milk for a Vitamin K source, which contains only trace amounts of the vitamin, and they may not store enough Vitamin K in their bodies as well. 

The danger

The danger in newborns lacking Vitamin K is that they can develop Vitamin K deficiency-related bleeding (VKDB), which occurs in three different stages:

  • 1. Early onset. This type of bleeding most commonly occurs within 24 hours of age and is seen most frequently in babies whose mothers took drugs that could inhibit Vitamin K production, such as certain antibiotics or barbiturates. 
  • 2. Classic. Occurs with delayed or insufficient feeding and can develop up to a week after birth, although it is still pretty rare. 
  • 3. Late onset. Happens in infants who are excessively breastfed and can occur up to 12 weeks after birth. According to experts, "In fully breast-fed infants who did not receive vitamin K at birth, the incidence is between 1/15,000 and 1/20,000." The AAP also states that late onset can occur up to six months and that the risk of late onset deficiency developing in infants who didn't receive the Vitamin K shot can be up to 81 times higher. 

    The Vitamin K shot

    Due to the dangers associated with a Vitamin K deficiency, the American Academy of Pediatrics recommended a prophylactic (preventive) dose of Vitamin K to be given to all newborns in a policy in the 1960's. They also revisited the policy in 2009 and reaffirmed it should still be given. 

    Side effects

    ​Many parents, of course, would like to know if there are any side effects to the Vitamin K shot. For such a small risk to babies (late onset only occurs in exclusively breastfed babies in 1.7% of babies), should all babies really be given the Vitamin K shot?

    The American Academy of Pediatrics set out to answer this question and dispel concerns that Vitamin K was linked to leukemia in an intensive report.  They concluded that the shot was shown to prevent the risk of VKDB and that any links to cancer have not been proven, so they continue to recommend that the shot be given to all newborns. Risks of the Vitamin K shot are mostly from the shot itself and include irritation at the injection site, infection, and in very rare cases, muscle damage.

    You can also ask for an oral version of Vitamin K, although the AAP recommends the injected version. 


    Lippi, G & Franchini, M. Vitamin K in neonates: fact and myths. Blood Transfus. 2011 Jan; 9(1): 4–9. Accessed April 21, 2015: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3021393/. 

    Where We Stand: Administration of Vitamin K. The American Academy of Pediatrics. Healthy Children.org. Accessed April 21, 2015 online: http://www.healthychildren.org/English/ages-stages/prenatal/delivery-beyond/Pages/Where-We-Stand-Administration-of-Vitamin-K.aspx. 

    Controversies Concerning Vitamin K and the Newborn. American Academy of Pediatrics. Accessed April 21, 2015http://pediatrics.aappublications.org/content/112/1/191.full.pdf

    Vitamin K and childhood cancer: a report from the United Kingdom Childhood Cancer Study. Accessed online April 21, 2015: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2394315/. 

    Vitamin K prophylaxis and Vitamin K Deficiency Bleeding. NW Newborn Clinical Guideline-Vitamin K. Accessed online April 21,2015: http://www.adhb.govt.nz/newborn/Guidelines/Blood/VitaminK.htm. 

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