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Fat-soluble vitamin / supplement

Vitamin K: uses, side effects & precautions

Also known as Phytomenadione, Phylloquinone (K1), Menaquinone (K2), Vitamin K supplement, Konakion.

Diese Informationen dienen ausschließlich der allgemeinen Orientierung und stellen keine medizinische Beratung dar. Konsultieren Sie bei persönlichen gesundheitlichen Anliegen stets eine qualifizierte medizinische Fachkraft. Wählen Sie im Notfall Ihre örtliche Notrufnummer.

What it is used for

  • Treating and preventing vitamin K deficiency
  • Given to newborns to prevent serious bleeding (vitamin K deficiency bleeding)
  • Helping reverse the effect of certain blood thinners under medical supervision
  • Supporting people with fat-absorption problems

How it works

Vitamin K is needed for the body to make several proteins involved in blood clotting and bone health. Without enough, blood does not clot properly and bleeding can occur, which supplementing prevents or treats.

How it is taken

Available as tablets, drops and as an injection given by a healthcare professional, including the dose commonly given to newborns. It is fat-soluble and oral forms are often taken with food. It is given exactly as your doctor or the label directs, particularly when used to manage blood-thinner effects.

No doses here on purpose. The right strength and schedule depend on you — only a doctor or pharmacist should set them. Always follow your prescription and the label.

Common side effects

  • Usually well tolerated
  • Mild stomach upset (uncommon)
  • Reaction at the injection site

Serious effects — get help

  • Rarely, a serious allergic reaction with injection, including difficulty breathing
  • Signs of an allergic reaction such as rash or swelling

If a reaction is severe — for example trouble breathing, swelling of the face or throat, or collapse — go to the nearest emergency room now or call your local emergency number. Do not wait for an online consultation.

Interactions to watch

  • Warfarin and similar blood thinners, whose effect vitamin K reduces
  • Bile acid binders and orlistat, which reduce absorption
  • Long-term antibiotics, which can lower the body's vitamin K

Who should take care

  • If you take warfarin, keep your vitamin K intake steady and do not start supplements without advice, as they affect how the medicine works
  • Tell your clinician about fat-absorption problems or liver disease
  • Newborn vitamin K is routinely recommended to prevent serious bleeding; discuss with your healthcare team
  • Discuss use in pregnancy and breastfeeding with your clinician

Frequently asked questions

Why are newborn babies given vitamin K?
Babies are born with very low vitamin K and cannot make enough yet, which puts them at risk of serious bleeding. A dose after birth prevents this. Your healthcare team will discuss the options with you.
I take warfarin. Can I take a vitamin K supplement?
Vitamin K reduces warfarin's effect, so you should not start or change supplements or make big diet changes without telling your clinician, who monitors your blood clotting.
What foods are high in vitamin K?
Green leafy vegetables such as kale and spinach are rich in vitamin K. If you take warfarin, aim to keep your intake consistent rather than avoiding these foods entirely.
Is vitamin K deficiency common?
It is uncommon in healthy adults but can occur with fat-absorption problems, liver disease, or long-term antibiotic use.
Is Vitamin K safe to take?
For most people it is safe when taken exactly as a doctor or pharmacist advises and as printed on the label. Tell your clinician about your other medicines and health conditions, and seek urgent care for any serious reaction.

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