DL-Methionine in dog and cat food

Is it OK for dogs and cats?

Dogs

At the amounts used to balance complete dog foods, DL-methionine is not a known concern: methionine is an essential amino acid, and EFSA judged supplementation to meet requirements safe. Vets also use DL-methionine to acidify urine when managing struvite stones, but Merck says long-term acidification can be harmful and should only follow a full veterinary evaluation.

Cats

Cats need methionine too, and it is generally the most limiting amino acid in cat food made from animal ingredients. FEDIAF sets a nutritional maximum for kitten growth foods (1.30 g per 100 g dry matter), and, as in dogs, deliberate urine acidification belongs with a vet.

How settled this is: Depends on the amount

What DL-Methionine is

DL-methionine is a feed-grade form of the amino acid methionine. EFSA has assessed DL-methionine and its sodium salt, together with methionine hydroxy analogues, as nutritional sources of methionine for all animal species. In US federal feed rules (21 CFR 582.5475), methionine is listed as generally recognised as safe for use in animal feed under good manufacturing or feeding practice.

Why it is in pet food

Complete foods are formulated to meet minimum amino-acid levels, and FEDIAF publishes minimums for methionine and for methionine plus cystine in dog and cat foods. A review of cat metabolism notes that methionine is generally the most limiting amino acid in cat diets formulated from animal-source ingredients. FEDIAF also notes that some lamb-and-rice dog foods may need more methionine. Separately, Merck lists DL-methionine, with ammonium chloride, as a urine acidifier of choice when managing struvite (magnesium ammonium phosphate) stones.

What it does in the food

Methionine is an essential amino acid in all animal species and is used to build body protein. EFSA found DL-methionine an effective source of methionine for protein synthesis in monogastric animals; the hydroxy analogues were somewhat less effective. Methionine is also the starting point for SAMe, a universal methyl donor for the body's methylation reactions, and the body can make cysteine from it. Dogs make taurine from methionine and cysteine, which is why taurine is generally not considered essential for dogs. Cats have higher requirements for sulfur amino acids and, unlike dogs, need taurine in their diet.

Safety and limits

EFSA concluded that adding methionine and its analogues in appropriate amounts to meet requirements is safe for the target animals; it did not support adding them to drinking water. FEDIAF lists no nutritional maximum for methionine in dog food but sets one for kitten growth foods: 1.30 g per 100 g dry matter (3.25 g per 1,000 kcal). DL-methionine acidifies urine. Merck gives ideal urine pH as 7.0-7.5 for dogs and 6.3-6.6 for cats, and notes that chronic urine acidification, and the acidosis that follows, can be harmful and should not be started without a complete evaluation of the animal. In FDA's dilated cardiomyopathy (DCM) investigation, average methionine and methionine-cystine levels were similar in the grain-free and grain-containing dog foods tested. FDA said in December 2022 that it did not plan further public updates until there is meaningful new scientific information.

What depends on the amount and the recipe

What matters is the total methionine and cystine the whole recipe supplies against FEDIAF minimums and, for kittens, the nutritional maximum. Species and life stage matter: the maximum applies to kitten growth foods, and cats need more sulfur amino acids. FEDIAF notes that dogs fed foods low in sulfur amino acids, some lamb-and-rice foods, and breeds such as Newfoundlands can have low taurine status, which added taurine or more methionine and cysteine can prevent. Deliberate urine acidification is a separate veterinary use.

Not the same as

• Methionine hydroxy analogue (MHA) and its calcium salt — A related methionine source rather than methionine itself; EFSA found the hydroxy analogues somewhat less effective than the DL-methionine forms.
• Taurine — A different sulfur-containing nutrient. Dogs can make it from methionine and cysteine; cats must get it from food.
• Cystine / cysteine — A different sulfur amino acid. FEDIAF sets targets for methionine alone and for methionine plus cystine, and the body can make cysteine from methionine.

Sources

1. Scientific Opinion on DL-methionine, DL-methionine sodium salt, the hydroxy analogue of methionine and the calcium salt of methionine hydroxy analogue in all animal species (EFSA Journal 10(3):2623) — EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP), via PubMed Central, 2012. Methionine is essential in all animal species; supplementation to meet requirements is safe for target species; DL-methionine is an effective methionine source for protein synthesis in monogastric animals, hydroxy analogues somewhat less effective; use in drinking water not supported.
2. Nutritional Guidelines for Complete and Complementary Pet Food for Cats and Dogs (September 2025) — FEDIAF (European Pet Food Industry Federation), 2025. Minimum methionine and methionine + cystine levels for dogs and cats; no maximum for dogs; nutritional maximum for kitten growth of 1.30 g/100 g DM (3.25 g/1000 kcal); lamb-and-rice foods may need more methionine; dogs synthesise taurine from methionine and cysteine; low taurine status with low sulfur amino acids, lamb-and-rice foods and in Newfoundlands.
3. Controlling Urine pH in Animals (full review Nov 2023, updated Sept 2024) — Merck Veterinary Manual, 2024. Ideal urine pH in dogs and cats; DL-methionine and ammonium chloride are urine acidifiers of choice for struvite; chronic acidification and acidosis can be harmful and need complete evaluation first.
4. 21 CFR 582.5475 Methionine (CFR 2025 edition) — US Code of Federal Regulations, via govinfo.gov, 2025. Methionine is generally recognised as safe in animal feeds under good manufacturing or feeding practice.
5. Verbrugghe A, Bakovic M. Peculiarities of One-Carbon Metabolism in the Strict Carnivorous Cat and the Role in Feline Hepatic Lipidosis. Nutrients 5(7):2811-2835 — Nutrients (MDPI), via PubMed Central, 2013. Methionine is generally the most limiting amino acid in cat diets from animal sources; cats have higher sulfur amino acid requirements; methionine forms SAMe, a universal methyl donor; cysteine can be made from methionine; cats need dietary taurine.
6. FDA Investigation into Potential Link between Certain Diets and Canine Dilated Cardiomyopathy — US FDA Center for Veterinary Medicine, 2022. Dogs synthesise taurine from cysteine and methionine; methionine and methionine-cystine similar in grain-free and grain-containing products tested; December 2022 statement that no further public updates are planned until meaningful new scientific information.

Checked against these sources on 2026-10-15. Definitions are in our own words. This is a reading aid, not veterinary advice: a vet who knows your animal comes first.