was ist k3 vitamin — when to see a doctor?

Vitamin K3 (menadione) is a synthetic form of vitamin K not recommended for human supplementation. Unlike natural K1 (phylloquinone) and K2 (menaquinone), K3 can cause oxidative stress and has been linked to liver toxicity and hemolytic anemia. It is rarely used in human medicine and appears mainly in animal feed. You should see a doctor if you are considering taking K3, or if you experience symptoms such as unusual bleeding, bruising, jaundice, or fatigue. Medical advice is also warranted if you suspect a vitamin K deficiency due to conditions like chronic gut disease, liver issues, or anticoagulant use. Evidence for any benefit of K3 in humans is weak, while its risks are well documented. Always consult a healthcare professional before taking any K3 product.