was ist vitamin k3 — which blood markers matter?

Vitamin K3 (menadione) is a synthetic form of vitamin K that is not recommended for human supplementation due to potential toxicity, including oxidative stress and liver damage. It is still used in some animal feeds. Regarding blood markers that matter for vitamin K status: PIVKA-II (des-gamma-carboxy prothrombin) is a functional marker that rises in vitamin K deficiency; undercarboxylated osteocalcin (ucOC) reflects bone vitamin K status; and direct measurement of vitamin K1 (phylloquinone) and K2 (menaquinone) in serum. However, these markers are relevant for natural vitamin K forms, not specifically for K3. Evidence for any beneficial effect of K3 in humans is weak and mostly mechanistic. In practice, K3 is rarely used in human supplements. Caveat: None of the provided context sources address vitamin K3 or related blood markers. This answer is based on general medical knowledge.