Menadione Sodium Bisulfite Complex (Vitamin K3) in dog and cat food

Is it OK for dogs and cats?

Dogs

The cited sources do not show a problem at the levels used in feed. EU scientists concluded in 2014, and again in 2025, that this vitamin K3 source is safe for all animal species when used as authorised. The EU renewed its authorisation in 2026. These were assessments for all animal species, not studies focused on dogs. Dogs usually get enough vitamin K from gut bacteria.

Cats

The same conclusion applies to cats, and in fish-rich canned cat food adding the vitamin matters. In a 1996 report, cats fed two canned foods high in salmon or tuna developed vitamin K deficiency, and some died. AAFCO's cat food profiles ask for added vitamin K where more than a quarter of the food, once its water is taken out, is fish. The EU assessments were not studies focused on cats. In a small 1942 study, two cats given menadione at many times the level in cat food for 72 days showed no adverse effects on their blood or tissues. Cats' red blood cells are more easily damaged by oxidation than dogs', but no such harm has been reported from menadione at the levels used in food.

How settled this is: A popular concern the sources do not support

What menadione sodium bisulfite complex (vitamin k3) is

Menadione is a synthetic form of vitamin K. It lacks the side chain found in the natural forms, vitamins K1 and K2. Menadione sodium bisulphite (MSB) is the sodium bisulfite addition compound of menadione, made by chemical synthesis, a white to yellowish crystalline powder. An AAFCO expert panel describes MSB as identical to MSBC (the name on US labels), except that it is not complexed with additional bisulfite. In the EU it is authorised as a nutritional feed additive for all animal species under identification number 3a710. That authorisation was renewed in September 2026 and runs until 14 October 2036. The additive must be at least 96% MSB complex, equal to at least 50% menadione. It may contain no more than 45 mg/kg of chromium III and IV. A chromium compound (sodium dichromate) is used as a catalyst in its manufacture. For labelling, the EU treats 1 mg of vitamin K3 as equal to 1 mg of menadione or 2 mg of MSB. FEDIAF lists 1 mg of MSB as supplying 0.51 mg of menadione. In the US, FDA stated in the Federal Register (1983 and 1990) that menadione and MSBC are prior-sanctioned for poultry feed at 2 to 4 g per ton, and that no vitamin K substance it knew of was generally recognised as safe; under its 1990 notice any other use needs a food additive regulation, and none exists for MSBC. Its use in pet food rests on the enforcement discretion of FDA and many state regulators (at least one state is reported to have acted against it around 2020, on legal grounds rather than safety), and on a 2021 AAFCO expert panel's recommendation that MSBC may be used as a source of vitamin K activity in the food of all animals. FDA's animal feed page says MSBC is widely used in pet foods. The sections 21 CFR 573.620 and 573.625 cover two other menadione salts, not MSBC.

Why it is in pet food

Vitamin K is an essential vitamin for dogs and cats. A deficiency causes slow blood clotting and excessive bleeding. Gut bacteria usually make enough, so most vitamin K in the body's tissues comes from bacteria. Conditions that upset gut bacteria, such as antibiotic treatment, can lead to deficiency. FEDIAF sets no minimum for vitamin K in dog or cat food. For dogs, it says vitamin K does not need to be added unless the diet contains antimicrobial or anti-vitamin compounds. For cats, it says vitamin K usually does not need to be added, but that canned foods high in fish may raise the risk of slow clotting, so adding it to such foods has been suggested. AAFCO's cat food profiles set 0.1 mg of vitamin K per kg of food, with its water taken out, for growth and for adult maintenance, and say it does not need to be added unless more than 25% of the food on that basis is fish. FEDIAF cites a 1996 report among its sources: cats offered two commercial canned foods high in salmon or tuna developed vitamin K deficiency, some queens and kittens died, and the survivors recovered with vitamin K. Its authors recommended that canned foods made mainly from fish carry more than 60 micrograms of vitamin K1 per kg. EFSA regards MSB as an effective source of vitamin K in animal nutrition.

What it does in the food

It provides vitamin K activity. Menadione has to be prenylated (gain a side chain) in the body to become active. EFSA notes that vitamins K1, K2 and K3 are all activated in the liver. There they act as co-factors that switch on vitamin K-dependent proteins, which the body needs for normal clotting. Vitamin K is one of the fat-soluble vitamins. The EU authorisation sets no minimum or maximum level in feed and requires the additive to be added through a premixture.

Safety and limits

In 2014, EFSA's feed additives panel (FEEDAP) concluded that MSB is safe for all animal species at practical use levels in feed. It found that acute toxicity of menadione or its derivatives is reached only at levels at least 1,000 times above requirements, and saw no need to set a maximum content. In its renewal assessment, adopted in November 2025, the panel found no new evidence to change that conclusion. The European Commission then renewed the EU authorisation for all animal species in September 2026, again with no maximum level. These were assessments for all animal species, not studies focused on dogs or cats. The two new target-animal studies the panel considered in 2025 were in fish. The Merck Veterinary Manual describes vitamin K toxicity in dogs and cats as extremely rare. EFSA's other concerns are about people who handle the additive and about drinking water, not pet food. MSB irritates the eyes and should be treated as a skin sensitiser. In 2025 EFSA said that handlers' exposure by any route, including breathing in its dust, is a risk and should be kept to a minimum. The 2026 EU rules require feed businesses to manage handlers' exposure to chromium through breathing or skin contact. Where that risk cannot be removed, breathing, eye and skin protection must be used. In 2014 EFSA also noted that giving MSB in drinking water is likely to raise animals' exposure to chromium(VI). Industry figures cited by AAFCO's 2021 expert panel put typical use at 2 to 4 mg of MSBC per kg of cat food with its water taken out, and 3 to 5 mg for dogs. In the only cat feeding data that panel found, a small 1942 study, two cats given 2 mg of menadione per kg of body weight a day for 72 days, and two given 50 mg per kg of body weight a day for 13 days, showed no adverse effects on their blood or tissues; the panel calls those studies limited in design and detail. Cats are more prone than dogs to oxidative damage of red blood cells (Heinz bodies), but the reports of such damage involve vitamin K given as a treatment, by injection or at very high doses, not menadione at the levels used in food. FDA has not banned menadione. It is no longer used to treat vitamin K deficiency in people, after injections of it caused liver damage, jaundice and anaemia in infants, and menadione added to infant formula once caused anaemia and jaundice; a 1970 FDA withdrawal of a tablet combining aspirin and menadione was for lack of evidence that it worked. In 2026 FDA wrote that it is unaware of any apparent animal safety concerns where these ingredients are used under good manufacturing practice.

What depends on the amount and the recipe

Whether a food needs added vitamin K depends on the recipe and the animal. FEDIAF points to diets containing antimicrobial or anti-vitamin compounds, and to canned cat foods high in fish; AAFCO's cat food profiles to foods that are more than 25% fish once their water is taken out. A label shows neither how much fish a food holds nor how much vitamin K it supplies. The Merck Veterinary Manual notes that anything disturbing the gut bacteria, such as antibiotic treatment, can lead to deficiency. Safety conclusions apply to use as authorised: through a premixture, in feed, and meeting the purity and chromium limits.

Not the same as

• Vitamin K1 (phylloquinone) — The natural form of vitamin K found in green plants. It has a side chain that menadione lacks.
• Vitamin K2 (menaquinones) — Natural forms of vitamin K made by intestinal bacteria, not a synthetic additive.
• Menadione nicotinamide bisulfite (MNB) — A different menadione salt that also supplies niacin. It is authorised separately in the EU (3a711) and listed in 21 CFR 573.625 for chicken and turkey feed and for growing and finishing swine feed.
• Menadione dimethylpyrimidinol bisulfite (MPB) — Another menadione salt, listed in 21 CFR 573.620 for chicken and turkey feed and for growing and finishing swine feed.

Sources

1. EFSA FEEDAP Panel. Assessment of the feed additives menadione sodium bisulphite (3a710) and menadione nicotinamide bisulphite (3a711) (vitamin K3) for all animal species for the renewal of their authorisation. EFSA Journal 23(12):e9792 — European Food Safety Authority (EFSA), 2025. Adopted 19 November 2025; MSB is made by chemical synthesis as a white to yellowish crystalline powder; at least 96% purity (at least 50% menadione); 45 mg/kg chromium limit; sodium dichromate catalyst; the 2014 opinion saw no need for a maximum content; no new evidence to change the conclusion that it is safe for target species; the two new target-animal studies were in fish; handlers' exposure by any route is a risk and should be minimised; inhalation exposure is likely.
2. EFSA FEEDAP Panel. Scientific Opinion on the safety and efficacy of vitamin K3 (menadione sodium bisulphite and menadione nicotinamide bisulphite) as a feed additive for all animal species. EFSA Journal 12(1):3532 — European Food Safety Authority (EFSA), 2014. K1 is found in green plants and K2 is made by intestinal bacteria; menadione is synthetic vitamin K without a side chain and must be prenylated to become active; K1, K2 and K3 are activated in the liver as co-factors for vitamin K-dependent proteins; acute toxicity at least 1,000 times above requirements; safe for all species at practical use levels; drinking water likely to raise chromium(VI) exposure; eye irritant and skin sensitiser; effective source of vitamin K.
3. Commission Implementing Regulation (EU) 2026/2115 – renewal of the authorisation of menadione sodium bisulphite (vitamin K3) and menadione nicotinamide bisulphite (vitamin K3) as feed additives for all animal species, repealing Implementing Regulation (EU) 2015/2307 — EUR-Lex (Publications Office of the European Union), 2026. Renewal of 3a710 for all animal species until 14 October 2036; no minimum or maximum content; premixture required; purity at least 96% MSB complex, equal to at least 50% menadione; chromium no more than 45 mg/kg; labelling equivalence 1 mg K3 = 1 mg menadione = 2 mg MSB; feed businesses must manage chromium exposure by inhalation or skin, with breathing, eye and skin protection where needed; MNB authorised separately as 3a711.
4. FEDIAF Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs (September 2025) — FEDIAF – European Pet Food Industry Federation, 2025. No vitamin K minimum for dogs or cats; vitamin K need not be added for dogs unless antimicrobial or anti-vitamin compounds are present; some indication that high-fish canned cat foods raise the risk of prolonged clotting, so supplementing them has been suggested; 1 mg MSB = 0.51 mg menadione.
5. Nutritional Requirements of Small Animals (Merck Veterinary Manual, full review Nov 2023, updated Sept 2024) — Merck & Co. / Merck Veterinary Manual, 2024. Vitamin K is essential for dogs and cats; gut bacteria usually supply enough and most tissue vitamin K is of bacterial origin; antimicrobial treatment can cause deficiency; deficiency causes prolonged clotting and bleeding; vitamin K toxicity is extremely rare; vitamin K is fat-soluble.
6. 21 CFR 573.620 Menadione dimethylpyrimidinol bisulfite, Code of Federal Regulations, 2024 edition — U.S. Government Publishing Office (govinfo), 2024. MPB is a separate menadione salt permitted to prevent vitamin K deficiency in chicken and turkey feeds and in growing and finishing swine feeds.
7. 21 CFR 573.625 Menadione nicotinamide bisulfite, Code of Federal Regulations, 2024 edition — U.S. Government Publishing Office (govinfo), 2024. MNB is a separate menadione salt, which also supplies niacin, permitted in chicken and turkey feeds and in growing and finishing swine feeds.
8. Vitamin K Substances and Animal Feed (FDA Center for Veterinary Medicine; content current as of 24 October 2024) — U.S. Food and Drug Administration, 2024. Menadione and MSBC are the prior-sanctioned vitamin K substances; both are also widely used in other animal feeds, including pet foods; adverse effects in horses come from injection.
9. Vitamin K Active Substances in Animal Feeds; Notice Concerning Food Additive Status, Docket 75P-0248, 55 FR 50777 (10 December 1990) — U.S. Government Publishing Office (Federal Register), 1990. Recalls FDA's 1983 conclusion that no vitamin K active substance it knew of was GRAS, but that menadione and MSBC were prior-sanctioned for poultry feed at 2 to 4 g per ton; any other use requires a food additive regulation.
10. Recommendations for Use of Menadione Sodium Bisulfite Complex (MSBC) in Animal Feed (AAFCO expert panel, 2021) — Association of American Feed Control Officials (AAFCO), 2021. The panel recommended MSBC as a source of vitamin K activity in the food of all animals in the US; MSB is identical to MSBC but not complexed with additional bisulfite; typical inclusion 2 to 4 mg/kg in cat food and 3 to 5 mg/kg in dog food (industry survey); Ansbacher 1942 cat and dog feeding data, limited in design; red blood cell damage reported where menadione was given intravenously.
11. PFC Proposed Revisions to the AAFCO Dog and Cat Food Nutrient Profiles (2013 Annual Meeting, Appendix C), accepted by Pet Food Committee e-vote on 2 July 2014 — Association of American Feed Control Officials (AAFCO), 2014. Cat food nutrient profiles: vitamin K 0.1 mg/kg dry matter for growth and reproduction and for adult maintenance, no maximum; footnote: vitamin K need not be added unless the diet contains more than 25% fish on a dry matter basis.
12. Strieker MJ, Morris JG, Feldman BF, Rogers QR. Vitamin K deficiency in cats fed commercial fish-based diets. J Small Anim Pract 1996;37(7):322-6 (PMID 8840252) — PubMed (U.S. National Library of Medicine), 1996. Clinical vitamin K deficiency in cats offered two commercial canned diets high in salmon or tuna; some queens and kittens died, survivors had prolonged clotting times and recovered with vitamin K; canned diets made mainly from fish should contain more than 60 micrograms of vitamin K1 per kg.
13. Lakeside Laboratories; Menacyl Tablets: Notice of Withdrawal of Approval of New Drug Application (NDA 6363), 35 FR 11827 (23 July 1970) — U.S. Government Publishing Office (Federal Register), 1970. The aspirin, menadione and ascorbic acid tablet lost its approval for lack of substantial evidence that it was effective as a fixed combination, not for toxicity.
14. Vitamin K (Linus Pauling Institute Micronutrient Information Center, reviewed July 2022) — Oregon State University, Linus Pauling Institute, 2022. Menadione given by injection induced liver toxicity, jaundice and haemolytic anaemia in infants, so it is no longer used to treat vitamin K deficiency.
15. Vitamin K Toxicity (Merck Manual Professional Version, full review June 2026) — Merck & Co. / Merck Manuals, 2026. Menadione, a synthetic vitamin K precursor used mainly in animal feed, caused haemolytic anaemia, hyperbilirubinaemia, jaundice and kernicterus in infants, historically in menadione-supplemented formula, which no longer occurs.
16. Hematology in Hepatic Disease in Small Animals (Merck Veterinary Manual, updated November 2024) — Merck & Co. / Merck Veterinary Manual, 2024. Cats are at higher risk than dogs of circulating Heinz bodies; Heinz body haemolysis was seen in cats with liver disease given repeated vitamin K1 injections.
17. The new argument on Menadione Sodium Bisulfite Complex (TruthaboutPetFood.com, 21 April 2020), quoting Dr. David Dzanis in PetFoodIndustry.com — TruthaboutPetFood.com, 2020. At least one state feed control official took action against pet products containing MSBC, because the AAFCO Official Publication's listing refers to poultry only (a legal reading, not a safety finding; the state is not named; a secondary source).
18. The puzzle of Menadione Sodium Bisulfite Complex (TruthaboutPetFood.com, 26 March 2026), quoting FDA Center for Veterinary Medicine's reply — TruthaboutPetFood.com, 2026. FDA has not initiated regulatory action against pet foods containing menadione or MSBC, and is unaware of any apparent animal safety concerns where they are used under good manufacturing practice (FDA's words as quoted; a secondary source).

Checked against these sources on 2026-10-25. Definitions are in our own words. This is a reading aid, not veterinary advice: a vet who knows your animal comes first.