Menadione (Vitamin K3)
Also known as: menadione sodium bisulfite
A synthetic form of vitamin K used in pet food that's been banned from human supplements since the 1960s.
What it actually is
Menadione is a synthetic precursor the body converts to vitamin K2. Cheaper than natural K1 (from leafy greens) or K2 (from fermented foods and organ meats).
Why it's used in dog food
Used in kibble as a cheap way to add vitamin K to the vitamin premix.
A bit of history
Banned by the US FDA from over-the-counter human supplements in 1963 after studies linked it to liver toxicity and hemolytic anemia at high doses. Remains legal in animal feed and pet food.
Pros
- •Cheap and effective source of vitamin K activity
Cons
- •Banned from human supplements since 1963
- •Linked to liver damage and red blood cell destruction at high doses
- •Natural vitamin K1 (from spinach, kale, alfalfa) or K2 (from organ meats) is safer
- •The dose in kibble is well below toxic thresholds — but why not use the natural form?
Safety notes
The dose in commercial pet food is below acute toxic levels. The concern is chronic low-dose exposure and the availability of safer alternatives.
Sourcing & quality
Foods using natural vitamin K sources (leafy greens, alfalfa, organ meats) are a cleaner choice.
Commonly found in
Skip this if…
You want a cleaner ingredient panel — natural K1/K2 sources exist.
The verdict
Not acutely dangerous at food doses, but a marker of a cost-driven formulation.