Vitamin K (Phytomenadione)

How it works

It is an essential cofactor for the hepatic gamma-carboxylation of clotting factors II, VII, IX and X (and proteins C and S), enabling synthesis of functional coagulation factors that newborns are otherwise deficient in.

Prescribing in practice

• Routine prophylaxis is recommended for all newborns because vitamin K deficiency bleeding, including late and intracranial bleeding, can be severe or fatal and is largely preventable.
• The intramuscular route gives reliable single-dose protection, whereas the oral route requires a multi-dose schedule and is less protective against late bleeding, particularly with exclusive breastfeeding or cholestasis.
• Administer according to the SPC and local neonatal policy, ensuring the correct neonatal preparation and route are used.

Monitoring

Routine laboratory monitoring is not required for prophylaxis; ensure any oral schedule is completed and remain alert to bleeding in infants with malabsorption or cholestasis.

Counselling the patient

• Explain that vitamin K is offered to all newborns to prevent a rare but serious bleeding problem.
• A single injection gives the most reliable protection; if the oral route is chosen, all the scheduled doses must be completed.
• Breastfed babies are at higher risk, so completing the recommended vitamin K is particularly important.

Evidence & guidelines

Routine neonatal vitamin K prophylaxis is long-established UK practice endorsed by national guidance, with intramuscular administration recognised as the most effective route for preventing vitamin K deficiency bleeding.