Menadione (Synthetic Vitamin K3)

Vitamin K is needed for blood clotting, and deficiency can occur with fish-heavy foods. AAFCO requires it in cat foods containing more than 25 percent fish.

Menadione is a synthetic compound with vitamin K activity, usually added as menadione sodium bisulfite complex (MSBC). A 2021 AAFCO expert panel recommended that MSBC may be used as a source of vitamin K activity in food for all animals in the United States, and it cited small feeding studies in cats and dogs at doses far above nutritional levels. Ask your veterinarian about any concern for a cat with a clotting or liver condition.

Source: aafco.org

Menadione sodium bisulfite complex, or MSBC, is a water-soluble form of menadione, also called vitamin K3. Cat food makers add it as a source of vitamin K activity. The AAFCO expert panel document says MSBC is widely used in pet foods and in feeds for poultry and other animals, at a few milligrams per kilogram of food.

Source: aafco.org

Vitamin K1, or phylloquinone, is the form found in green plants. Vitamin K3, or menadione, is a synthetic compound that the body converts into an active vitamin K form. The AAFCO MSBC document mentions phylloquinone as a separate vitamin K source that has its own review for use in pet foods.

Source: aafco.org

Some cat food makers leave menadione out and rely on vitamin K that is present in other ingredients, or they use another vitamin K source. Reports of problems with menadione come from high doses or injection, according to the AAFCO MSBC review, which also notes that the feeding studies in cats were small. Brands that skip it are making a formulation choice; labels show which form, if any, a food uses.

Source: aafco.org

Pettings gives menadione 0 out of 5 and labels it "Contains menadione (synthetic vitamin K3)." It appears on 48 of the 149 dry cat foods we list. Our How We Score page explains how ingredient scores are set. Each food's page shows how it scores overall.