What to Know About the Vitamin K Shot for Newborns

Medically Reviewed by Dan Brennan, MD on August 06, 2022
4 min read

Life as a newborn isn't easy. On top of being exposed to a whole new environment, they're tested, prodded, and poked. One of those pokes is a Vitamin K shot, a routine part of post-birth care for newborns.

Vitamin K is one of many vitamins our bodies need to stay healthy. It’s a fat-soluble vitamin, meaning excess vitamin K gets stored in the liver and fat tissue. And unlike some other vitamins, your body can make vitamin K on its own. Another way to get vitamin K is by eating leafy greens.

What is Vitamin K Good For? Vitamin K has two very important roles in the body. The first job is to help with blood clotting, which is a necessary bodily function that prevents you from bleeding out when you get injured. The second role of vitamin K is to help keep your bones healthy.

Everyone needs vitamin K to keep their body healthy. Unfortunately, newborn babies don’t have the same store of vitamin K that adults and older kids have. Vitamin K is one of the few nutrients that can’t easily pass through the placenta, and their bodies don’t yet have the gut bacteria to make the vitamin K. Breastfeeding also does not offer babies a sufficient amount of vitamin K.

When a newborn doesn’t have enough vitamin K, it puts them at risk for something called vitamin K deficiency bleeding (VKDB). This means that if the baby bleeds, the blood can’t clot enough to stop the bleeding. VKDB can happen outside the body and inside the body, meaning your baby could be bleeding out internally and you wouldn’t be able to see it.

The vitamin K shot is essentially a preventative measure. While there’s no guarantee that low levels of vitamin K will be a problem for your baby, internal bleeding — especially brain bleeds — can be devastating.

The primary benefit of a vitamin K shot is that it prevents vitamin K deficiency bleeding. Half of all babies with VKDB get brain bleeds, which can lead to brain damage or death.

There are three types of vitamin K deficiency bleeding. These are:

  • Early-onset: Early-onset vitamin K deficiency bleeding is bleeding that occurs within 24 hours after birth and is typically caused because the birth-giving parent has been taking medications that interfere with vitamin K.
  • Classical: Classical vitamin K deficiency bleeding occurs between two days to one week after the baby is born. This type of vitamin K deficiency bleeding is most common and occurs somewhere between 1 in 60 and 1 in 250 newborn babies.
  • Late-onset: Late-onset vitamin K deficiency bleeding happens from one week after birth to up to six months after birth. This type is rarer than the others, occurring somewhere between 1 in 14,000 and 1 in 25,000 infants.

Newborns who do not get their vitamin K shot at birth are 81 times more likely to get late-onset vitamin K deficiency bleeding than babies who do get the shot. Vitamin K shots for newborns are extremely safe and highly recommended for all newborn babies. If you skip the shot and your baby gets a brain bleed, by the time symptoms emerge it may be too late.

The most common symptom of vitamin K deficiency is hemorrhaging, or excess bleeding. This may show up in many ways, including excess bruising, nose bleeds, a wound that won’t stop bleeding, bleeding in the stomach or intestine, and bleeding in the brain.

Internal bleeding is much harder to detect than a nosebleed or an open wound. Symptoms of bleeding from the stomach or intestines may include:

  • Vomiting blood 
  • Black, tar-like stool
  • Lightheadedness
  • Fainting
  • Difficulty breathing
  • Chest pain
  • Abdominal pain

Bleeding of the brain, also called intraventricular hemorrhage, may have the following symptoms:

  • High-pitched cry
  • Slow heart rate
  • Pauses in breathing
  • Lethargy
  • Coma
  • Seizures
  • Swelling of the soft spot of the baby’s head
  • Abnormal eye movement
  • Decrease in muscle tone and reflexes
  • Low red blood cell count
  • Pale or blue color to the skin

Internal bleeding is diagnosed through imaging. The type of imaging will depend on where the suspected bleed is, but it may be an ultrasound, X-ray, CT scan, or MRI. To diagnose a vitamin K deficiency as the cause of these symptoms, your baby’s doctor will do a blood test to check your baby’s levels of vitamin K.

The American Academy of Pediatrics highly encourages all babies to get the vitamin K shot. Time and time again, early intervention with the vitamin K shot has shown to be effective at preventing vitamin K deficiency syndrome and brain bleeds. As such, the American Academy of Pediatrics has issued the following recommendations:

1. All newborns weighing less than 1500 g (3.3 lbs) should have a single, intramuscular vitamin K shot of 1 mg within six hours of birth.

2. All newborns weighing over 1500 g (3.3 lbs) should have a single, intramuscular vitamin K shot of between 0.3 mg/kg to 0.5 mg/kg.

3. Healthcare providers should be well-educated on the benefits of the vitamin K shot and the risks of refusal, and must pass that information on to the baby’s caregivers.

4. Vitamin K deficiency bleeding should be considered when evaluating an infant’s bleeding within their first six months, even if they got the vitamin K shot, and especially for infants who exclusively nurse.