Vitamin K is a vitamin that plays an important role in blood clotting. Without it, the body cannot produce certain blood clotting factors, which can lead to bleeding.
Newborns are born with very low stores of vitamin K, so there is a risk of a condition called Vitamin K Deficiency Bleeding (VKDB).
For this reason, most pediatric associations worldwide recommend that newborns receive a prophylactic dose of vitamin K after birth.
Why do newborns have low levels of vitamin K?
Research shows several reasons why vitamin K stores are low in newborns:
- vitamin K crosses the placenta poorly
- the newborn’s intestines at birth do not yet have bacteria that produce vitamin K
- breast milk contains relatively small amounts of vitamin K
Because of this, newborns have lower activity of blood clotting factors in the first weeks of life, which can in rare cases cause bleeding.
Vitamin K Deficiency Bleeding
Research shows that in infants without vitamin K prophylaxis, the following occur:
- early and classic VKDB: approximately 250–1,700 cases per 100,000 births
- late VKDB: approximately 10–80 cases per 100,000 births.
If a newborn receives an intramuscular dose of vitamin K, the risk of late VKDB is reduced to approximately less than 1 case per 100,000 infants. Vitamin K deficiency bleeding is divided into three forms.
Early form
It occurs in the first 24 hours after birth. It is more common in infants whose mothers took certain medications during pregnancy (such as antiepileptics or anticoagulants).
Classic form
It occurs between days 2 and 7 of life. It most commonly presents as:
- bleeding from the umbilical cord
- gastrointestinal bleeding
- bruising or bleeding in the skin.
Late form
It occurs between 1 week and 6 months of age, most commonly between 2 and 8 weeks of life. This form is rare but can be very serious. In approximately 30–60% of cases, it involves bleeding in the brain, which can cause permanent neurological damage or death. There are no warning signs before life-threatening bleeding.
Infants without vitamin K have an 81 times greater risk of VKDB than infants who receive it (CDC, 2025).
How is vitamin K given to newborns?
Vitamin K is a fat-soluble vitamin needed for blood clotting. It is named after the German word for clotting—Koagulation or coagulation. The body cannot produce vitamin K on its own and stores it poorly. Vitamin K1 (also known as phylloquinone) is obtained from leafy green vegetables. We can also get vitamin K2 (menaquinone) from bacteria living in our digestive tract. Vitamin K1 from plants represents approximately 90% of our vitamin K intake, while vitamin K2 from bacteria represents only about 10% of our total intake (Shearer 2009; Lippi and Franchini 2011; Polin, Fox et al. 2011).
Vitamin K is needed by our body to activate certain molecules, also known as clotting factors, which help blood clot. Blood clotting factors are present in the body at birth, but they are not fully activated due to low levels of vitamin K. If we don’t have enough vitamin K, we cannot activate these molecules. So vitamin K deficiency reduces our blood’s ability to clot normally. Most of the time, our body can still clot blood adequately, even with low levels of vitamin K. However, when vitamin K levels drop lower and lower, we reach a point where our blood no longer clots and spontaneous bleeding occurs. The level at which bleeding occurs varies from person to person and is unpredictable (Shearer, 2009).
Intramuscular injection
The most common method is an intramuscular injection of vitamin K into the thigh muscle after birth.
Advantages:
- very effective protection
- lasts for several months
- only one dose is needed
Research shows that this method is most reliable in preventing late VKDB.
Slovenia follows the guidelines of the European Society for Paediatric Gastroenterology, Hepatology and Nutrition – ESPGHAN from 2016, which recommend giving 1 mg of vitamin K into the thigh muscle in the first hours after birth (Neonatal Section, 2021).
Newborns with risk factors, such as: premature infants, sick newborns, newborns whose mothers received certain medications during pregnancy, newborns born by vacuum delivery, and newborns with liver disease must receive vitamin K intramuscularly (Neonatal Section, 2021).
Oral vitamin K
In some countries, an oral form of vitamin K is also available, but it requires multiple doses.
For example:
- first dose at birth
- second dose after a few days
- additional doses in the following weeks
Oral regimens can be effective, but are less reliable than intramuscular injection, especially in preventing late VKDB. The reasons are mainly poorer absorption and the fact that doses must be consistently repeated. However, it is important that parents have a choice.
All developed countries implement vitamin K prophylaxis (in Sweden since 1940, in the USA since 1961, and in Slovenia since 1987). Since then, the incidence of internal organ bleeding in newborns has significantly decreased (Neonatal Section, 2021).
History of vitamin K administration to newborns
In 1894, Boston physician Dr. Townsend described 50 cases of bleeding in newborns. He described it as “hemorrhagic disease of the newborn.” Dr. Townsend was the first to identify a connection between poor or insufficient breastfeeding and bleeding in newborns (Shearer, 2009).
In 1930, a Danish biochemist discovered that vitamin K deficiency was the cause of unexpected bleeding in young chicks (Lippi and Franchini 2011).
In 1944, a Swedish study was published involving more than 130,000 infants who received 0.5 mg of vitamin K (either orally or by injection) on the first day after birth. The study showed that infants who received vitamin K were 5 times less likely to bleed in the first week after birth. They estimated that for every 100,000 full-term infants, vitamin K administration saves 160 infants per year (Lehmann 1944).
In 1961, the American Academy of Pediatrics recommended vitamin K administration immediately after birth. This practice has been the standard of newborn care in the USA ever since (AAP, 1961).
After 1999, the term “hemorrhagic disease of the newborn” was changed to “vitamin K deficiency bleeding” to indicate the cause of bleeding—that is, vitamin K deficiency. The new name also reflects the fact that some infants began bleeding later, that is, after the four-week “newborn period” (Shearer, 2009).
Breastfeeding and vitamin K
Breast milk contains relatively small amounts of vitamin K, so exclusively breastfed infants without prophylaxis are at greater risk for late VKDB (Evidence Based Birth, 2025; CDC; American Academy of Pediatrics).
Studies show that mothers of infants who developed late bleeding had normal levels of vitamin K in their milk. It is thought that perhaps some of these children had difficulty absorbing vitamin K from breast milk (Shearer, 2009).
Formula-fed infants and vitamin K deficiency
There are almost no reports of late vitamin K deficiency bleeding in formula-fed infants. The reason is that formula has relatively high concentrations of vitamin K1, approximately 55 micrograms per liter (Shearer 2009). However, this is not a reason not to exclusively breastfeed your child!
On average, formula-fed infants received more vitamin K1 than exclusively breastfed infants (45.4 micrograms per day compared to 0.55 micrograms per day). The vitamin K1 level in 6-week-old breastfed infants was around 0.13 micrograms per liter, compared to 6.0 micrograms per liter in formula-fed infants (von Kries Shearer et al. 1987; Greer, Marshall et al. 1991; Shearer 2009).
Is vitamin K safe?
Research shows that prophylactic vitamin K in newborns is safe. The most common side effects are mild pain, redness, or bruising at the injection site. Serious allergic reactions are very rare. In the 1990s, a study was published suggesting a possible link between vitamin K and leukemia, but subsequent larger studies did not confirm this link (Evidence Based Birth; CDC; American Academy of Pediatrics).
Cases of side effects from propylene glycol are rare and associated with very high doses. For example, in one case, infants received multivitamin supplements containing 300 mg of propylene glycol daily (Macdonald et al., 1987). The dose is approximately 30 times higher than in vitamin K injections and triggered seizures in some infants.
Allergic reactions to vitamin K have usually occurred with intravenous administration, which is not used in newborns.
Before 1960 (mainly in the 1950s), there were some reports of jaundice and anemia due to vitamin K; doses were not precisely defined at that time and a water-soluble version of vitamin K was used. Consequently, they began using the fat-soluble vitamin K that is used today. In 2014, researchers published a case report of an infant who had an allergic reaction to a vitamin K injection and went into anaphylactic shock. The child survived, but researchers could not determine why the newborn had this type of reaction (Koklu et al. 2014).
Any injection can cause irritation and redness at the site, but intervention is rarely needed. The injection can cause pain, which can be reduced by holding and breastfeeding the infant during the injection.
What are the possible consequences of late vitamin K deficiency bleeding? Although this form of bleeding is rare, the consequences can be severe. More than half of infants who develop this form of bleeding will bleed into the brain. The mortality rate for this form is approximately 20% (Shearer 2009; Lippi and Franchini, 2011). Another study that examined 131 cases worldwide showed an overall mortality rate of 14%. Of the surviving infants, about 40% had long-term brain damage. In countries with lower quality of living, many infants with late bleeding die before hospital admission, their diagnoses and deaths are not documented, and these cases are of course not included in statistics (Shearer 2009). One of the most dangerous facts about late bleeding is that it often cannot be recognized until it is too late. Infants cannot tell us what is happening, and symptoms of brain bleeding can sometimes be difficult to identify—such as feeding difficulties, lethargy, irritability. Unfortunately, brain bleeding can reach a critical size before parents seek medical help. It can also take time for medical staff to figure out what is wrong (Schulte et al. 2014).
Classic vitamin K deficiency bleeding and its consequences? The classic form, which occurs in the first week after birth, is more common than the late form. Data from older studies show that 0.25% to 1.5% of newborns (250 to 1,500 per 100,000) will develop classic bleeding if they do not receive vitamin K at birth, while newer estimates show the number is closer to 0 to 0.44% (0-440 per 100,000 births). This type of VKDB is usually mild and involves bleeding at the umbilical cord or circumcision site. Nevertheless, blood loss can be significant. The mortality rate for this form of bleeding in developed countries is very low (Lippi and Franchini, 2011).
How is vitamin K deficiency bleeding treated? The main treatment is vitamin K administration. When an infant receives a vitamin K1 injection, it will usually slow or stop bleeding within 20-30 minutes (Shearer, 2009). However, if bleeding occurs in the brain, the infant may already have brain damage by the time the medication is administered. Other forms of treatment that have been used in infants with late bleeding include blood transfusion and plasma transfusion, brain surgery and removal of accumulated blood, and anti-seizure medications (Dr. Robert Sidonio, 2014).
Conclusion
Newborns have very low stores of vitamin K at birth, so there is a small but serious risk of bleeding.
Research shows:
- without prophylaxis, there is a greater risk of VKDB
- intramuscular vitamin K very effectively reduces the risk
- oral regimens exist but are less reliable
Therefore, most professional recommendations recommend a single intramuscular dose of vitamin K after birth.
Sources and other contributions:
Prevention-Vitamin-K-Deficiency-Bleeding-in-Newborns-Explanations-for-Parents.pdf
Administration of Vitamin K to Newborns
Evidence on: The Vitamin K Shot in Newborns – Evidence Based Birth®
Protect Your Baby from Bleeds – Talk to Your Doctor about Vitamin K
Protect Your Baby from Bleeds | Vitamin K Deficiency Bleeding | CDC
Vitamin K and the Newborn Infant | Pediatrics | American Academy of Pediatrics
Vitamin K shots protect newborns from severe bleeding – AAP
Midwife Informed Consent for Vitamin K
General Discussion of Oral Vitamin K instead of Injected Vitamin K
Should You Give Your Baby Vitamin K At Birth?
Vitamin K prophylaxis and Vitamin K Deficiency Bleeding
Why not to clamp the cord early
The Potential Dark Side of the Routine Newborn Vitamin K Shot
Vitamin K for newborn babies – Information for parents (2010); NHMRC
Vitamin K at Birth: To Inject or Not
Evidence for the Vitamin K Shot in Newborns
Giving birth in hospital raises risk of new mothers bleeding to death
