Menadione (vitamin K3)

Menadione is the synthetic vitamin K (K3) the FDA pulled from human supplements over high-dose toxicity — yet it’s still the cheap default in many pet foods. The fuller picture: a 2021 AAFCO expert panel judged it safe at feed levels, and the FDA hasn’t moved against it. The worry is real only at high doses (it stresses red blood cells and the liver). Dogs make their own vitamin K from gut bacteria; cats on fishy diets may need a supplement. Premium brands use natural K1 instead — if you’d rather skip the synthetic, that’s the label to look for.