Vitamin K: black box warning misconceptions
- Alex Kelly
- Feb 14
- 6 min read
Updated: Apr 2
Vitamin K1 has a black box warning about the possibility of severe reactions, including fatalities with IV and IM administration. These reactions resemble hypersensitivity or anaphylaxis, including anaphylactoid reaction, and have led to shock and cardiac and/or respiratory arrest (1).
However, this warning is referring specifically to Vitamin K’s use as an antidote for too much Coumadin or Warfarin (blood thinning medications) given to adults in large, rapid doses to combat hemorrhaging (2) - NOT its use for VKDB in newborns.
Too much of anything, even a natural vitamin, can have negative side effects. It doesn’t mean, when dosed correctly, it’s “bad.” For example, Vitamin A has numerous benefits - including preventing and treating measles - but if taken in too large of a dose it can cause hypervitaminosis A. This doesn’t make Vitamin A bad. It all depends on the quality and quantity.
The Purpose of the Vitamin K Shot
The vitamin K shot helps prevent VKDB (vitamin K deficiency bleeding) in infants.
Babies are born with insufficient levels of vitamin K, which they need in order to stop life threatening and spontaneous bleeding. This bleeding can occur anywhere inside or outside of the body, but when the bleeding happens on the inside (especially in the skull) it can be extremely difficult to notice. This is rare, but when it does happen it’s pretty high stakes.
The Vitamin K shot enters the bloodstream and immediately increases the amount vitamin K in the blood. This provides enough so that the baby’s levels don’t drop dangerously low in the first few days of life. The rest of the vitamin K is released slowly over the next 2-3 months, providing a steady source until the baby has another source from their diet (4).
Newborn Vitamin K Reaction Stats
There are nearly 4 million births in the United States each year, and there have been zero cases of deaths, and only 1 recorded case of an allergic reaction in a baby in Turkey (3).
Vitamin K Deficiency Bleeding Stats
Early VKDB is the most common and least severe, occurring in
1 in 60 to 1 in 250 newborns (5-7)
Late VKDB is rarer and more severe, occurring in
1 in 14,000 to 1 in 25,000 infants (5-7)
Infants who do not receive a vitamin K shot at birth are 81 times more likely to develop late VKDB than infants who do receive a vitamin K shot at birth (4).
“But, the Vitamin K Shot is Synthetic”
Another misconception is that synthetic vitamins are “bad.” This is actually not always the case. In fact, sometimes synthetic vitamins are are actually more bioavailable for certain populations.
Synthetic vitamins are derived from a synthetic source, but go through various processes to isolate specific nutrients (ex vitamin A created from beta-ionone found in acetone) vs natural vitamins that are derived from a natural source, but go through various processes to isolate specific nutrients in the desired doses/potency (ex vitamin A created from beta-ionone found in lemongrass) (4.5)
Synthetic vitamins can be made in higher doses, produced with higher accuracy and puracy, more easily ensure no contaminants, and be created in better bio-available forms.
A Deeper Dive into Synthetic Vitamins
Synthetic vitamins are isolated from artificial sources like Vitamin A created from beta-ionone found in acetone. The end product is a nearly identical chemical structure that studies generally show positive health outcomes.
Reputable ingredient suppliers test their product to ensure that the vitamin they are creating is isolated from the original compound that they would not necessarily want in their finished product. Even when isolating something from a “natural” source, the source typically is not present in the final product.
Synthetic derivatives can oftentimes be more bioavailable. For example, the form of B12 sourced from food is typically a few steps behind (enzymatic process wise) when it comes to the form that is active in our body (5-MTHF). When an individual has certain gene SNPs that stop them from being able to perform this conversion from food into active form, synthetic vitamins may be the best option for them to fill a nutrient gap (4.5)
Vitamin K Shot and Jaundice?
There have been documented cases of Vitamin K being the cause of jaundice in newborns, but it’s important that we look at the facts. The first reports of extreme hemolytic anemia and hyperbilirubinemia were in the mid 1950s when high doses (50mg) of Vitamin K2 (menaione) were used. This lead to the abandonment of Vitamin K2 and the use of lower dose Vitamin K1 (phytonadione) (8,9).
Since then, the only cases of reported hyperbilirubinemia as a result of Vitamin K1 have been in extremely high doses (25-30mg), almost exclusively in premies. The normal Vitamin K1 dose is 0.5-1mg, of which there have been no reported cases of jaundice (10).
It is not my place or expertise to tell you 100% that the Vitamin K shot does or doesn’t cause jaundice.
I also acknowledge it is understandable why there is a widespread belief that the typical Vitamin K shot causes jaundice given the fact that it has caused jaundice in some babies (although we have to remember these cases are mostly in premies and in larger than normal doses), and that most babies receive this shot, AND that 60% of babies typically have jaundice to some extent (11).
However, right here and right now, given the scientific evidence, it does not appear as if the typical low dose of Vitamin K given to newborns causes jaundice. And given what we know about the top causes of jaundice, it could very well just be a simple numbers game based on a coincidence.
I am only one person, but both of my kids received the vitamin K shot. Once was jaundice, and the other was not. The one who was jaundice was born at 38 weeks via c-section, had delayed skin-to-skin, and not nearly the amount of skin-to-skin within the first 48 hours that my other did, and did not receive as much natural sunlight in the first few days. My second, who was not jaundice, was born at home at 40weeks1day, immediate skin to skin, constant skin to skin the first 24-48 hours, and was exposed to natural sunlight as soon as the sun was up and stayed that way throughout the day.
Vitamin K Shot Alternatives
Evidence Based Birth has tons of well-researched information on the vitamin k shot as well as alternatives - and the benefits and risks of each.
I highly recommend checking out:
They cover:
Greater detail on VKDB
History of newborn Vitamin K
Does delayed chord clamping raise Vitamin K levels?
Why do breastfed babies not have enough Vitamin K?
Are formula-fed babies protected against VKDB?
Vitamin K dosing
Ingredients in the shot
Does circumcision increase need for Vitamin K shot?
Can I just eat a high Vitamin K diet instead?
Info on the oral Vitamin K method
And more
Sources:
1 Britt RB, Brown JN. Characterizing the Severe Reactions of Parenteral Vitamin K1. Clin Appl Thromb Hemost. 2018 Jan;24(1):5-12. doi: 10.1177/1076029616674825. Epub 2016 Oct 21. PMID: 28301903; PMCID: PMC6714635.
2 Britt RB, Brown JN. Characterizing the Severe Reactions of Parenteral Vitamin K1. Clin Appl Thromb Hemost. 2018 Jan;24(1):5-12. doi: 10.1177/1076029616674825. Epub 2016 Oct 21. PMID: 28301903; PMCID: PMC6714635.
3 Koklu, E., Taskale, T., Koklu, S., & Ariguloglu, E. A. (2013). Anaphylactic shock due to vitamin K in a newborn and review of literature. The Journal of Maternal-Fetal & Neonatal Medicine, 27(11), 1180–1181. https://doi.org/10.3109/14767058.2013.847425
4.5 Madison Regev (@goodseedwellnessllc); nutrition consultant, research & product developer, and nutraceuticals expert
5 Hand I, Noble L, Abrams SA; AAP Committee on Fetus and Newborn, Section on Breastfeeding, Committee on Nutrition. Vitamin K and the Newborn Infant. Pediatrics. 2022;149(3):e2021056036
6 Zipursky A. Prevention of vitamin K deficiency bleeding in newborns. Br J Haematol 1999;104:430–7.
7 Sutor AH, Kries R, Cornelissen EAM, McNinch AW, Andrew M. Vitamin K deficiency bleeding (VKDB) in infancy. Thromb Haemost 1999;81:456–61.
9 Newborn Vitamin K Prophylaxis: A Historical Perspective to Understand Modern Barriers to Uptake Hosp Pediatr (2019) 9 (1): 55–60.
10 THE RELATION OF VITAMIN K TO HYPERBILIRUBINEMIA. Elizabeth Asteriadou-Samartzis; Sanford Leikin Pediatrics (1958) 21 (3): 397–402. doi.org/10.1542/peds.21.3.397
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