Vitamin K injection or by mouth – what's the difference?

If you choose the injection, then you only need one dose and you can be sure that your baby has received the Vitamin K. 

If you choose the oral option, your baby will need more doses and there is a possibility of the Vitamin K not being given properly. For example, you may forget to give it, or it may dribble out of your baby’s mouth. 

Informing Consent’s pharmacological adviser says: 

‘For oral administration, adverse effects attributable to the excipients themselves appear extremely uncommon.   

Oral Vitamin K is better tolerated regarding hypersensitivity, but IM (intra-muscular) is more reliable for rapid correction. In general, oral medicines are often better tolerated than injections because the digestive system and liver are designed to process and detoxify many substances before they reach the bloodstream.   

The main drawback is that absorption can be unreliable, especially in people with liver disease, bile flow problems, or malabsorption.’ 

‘To put it more briefly: 

Safety & Tolerance (Oral): Excellent tolerability with very rare excipient-related adverse effects. However, efficacy is limited by unreliable intestinal absorption, particularly in conditions like severe liver disease, cholestasis, or malabsorption.  

Safety & Tolerance (IM): Carries a risk of rare but serious anaphylactoid reactions; slow administration (over >30 seconds) is required to mitigate flushing, chest tightness, or shock. Local irritation or phlebitis may occur at the injection site.’  

Another of our medical advisers notes that: 

‘Babies given Vitamin K by injection have a rapid rise in their blood level to as much as 5000x higher than a normal newborn. This sudden rise can be avoided by using oral Vitamin K.’  

By avoiding an injection, you will avoid specific injection-related risks, but some practitioners argue that oral administration is less effective at preventing late VKDB. 

However, the Cochrane Library Review of a number of Vitamin K trials, ‘Prophylactic Vitamin K for Vitamin K deficiency bleeding in neonates’, found that both injection and oral administration are effective at preventing VKDB.  

The authors write: 

‘A single oral compared with a single intramuscular dose resulted in lower plasma Vitamin K levels at two weeks and one month, whereas a 3-dose oral schedule resulted in higher plasma Vitamin K levels at two weeks and at two months than did a single intramuscular dose.’ 

‘A single dose (1.0 mg) of intramuscular Vitamin K after birth is effective in the prevention of classic HDN.  

Either intramuscular or oral (1.0 mg) Vitamin K prophylaxis improves biochemical indices of coagulation status at 1-7 days.  

Neither intramuscular nor oral Vitamin K has been tested in randomized trials with respect to effect on late HDN.  

Oral Vitamin K, either single or multiple dose, has not been tested in randomized trials for its effect on either classic or late HDN.’ 

This study from Denmark, ‘Weekly oral Vitamin K prophylaxis in Denmark’, also supports the effectiveness of administering Vitamin K orally.  

Their conclusion is that ‘Weekly oral Vitamin K supplementation during the first 3 mo of life was an efficient prophylaxis against VKBD.’ 

This 2016 systematic review, ‘Vitamin K prophylaxis for prevention of Vitamin K deficiency bleeding: a systematic review’, states that: 

‘There is low-quality evidence from observational studies that routine IM administration of 1 mg of Vitamin K at birth reduces the incidence of late VKDB during infancy... Future studies should compare the efficacy and safety of multiple oral doses with IM Vitamin K and also evaluate the optimal dose of Vitamin K in preterm neonates.’ 

At Informing Consent, we would welcome more research into Vitamin K as highlighted by these reviews.