Lysine for Cats Foods, Benefits, Supplements and Toxicity

What is lysine?

Lysine ( denoted by Lys or K) is an essential α-amino acid used in protein biosynthesis and other functions. There are the D-and L enantiomers while the lysine hydrochloride (monohydrochloride) and acetate are its salts.

An α-amino acid has a carboxylic and amino group separated by single carbon, often known as the α-carbon and it is a basic amino acid together with arginine and histidine.

Furthermore, it has a positively charged side-chain and it is ketogenic (can undergo ketosis to form ketones used in energy production).

Finally, being basic, intestinal absorption is by the help of dibasic amino acid transporters while in the kidney, reabsorption occurs actively at the proximal tubules.

Do cats need lysine?
Do cats need lysine?

Lysine-rich cat foods

Some of the dietary natural sources of lysine include meat ( lean beef and lamb), poultry, cheese, and other dairy products, pork, fish (cod, tuna, sardines), shrimp and eggs.

Also, fruits (mangoes, apricots, pears, apples,), beans, lentils, wheat germ, soybeans, spirulina, among others have it.

Besides the dietary sources, there are supplements for not only cat and dogs but also human beings.

How much lysine to give a cat?

Based on dry matter AAFCO 2014 recommends that cats have at least 1.20% of lysine for growth and reproduction while for adult maintenance, the minimum amount is 0.83%. These amounts are 3.00g and 2.08g per 1000 kcal of cat food.

However, if you are using them therapeutically or as supplements, most of them have various dosages depending on the intended therapeutic use. Your vet will guide you on coming up with the right dosages.

Also, most manufacturers have recommended dosages which can act as a guideline in ensuring there are no overdose instances.

What does lysine do for cats – benefits or functions

What is lysine used for in cats? The answer is simple. It has various functions which include the following:-

  • It is a protein building block, i.e., it uses its positively charged side chain to binds with other molecules and it helps in DNA replication.
  • It boosts their immune system by helping in the synthesis of various antibodies and enzymes vital for a better immunity system.
  • It is a precursor for carnitine that aids in energy metabolism, i.e., carnitine takes fatty acids to mitochondria. It is also a precursor for hydroxylysine found in collagen (this helps it ensure a healthy skin).
  • According to, it aids in calcium absorption and thus, it helps in ensuring strong and healthy teeth and bones.
  • Supplementation helps reduce the severity of feline herpesvirus infection (Feline viral rhinotracheitis) and recovery duration. However, the role of this amino acid in treating feline herpesviral is under doubt with recent research that did not prove an effect on preventing replication of this virus and therefore not an effective treatment.
  • For cat’s eyes with viral conjunctivitis due to feline herpes, WikiVet notes, “oral supplementation (400 mg P.O q 24h to 500 mg P.O q 12h) has been shown to decrease both viral shedding and severity of conjunctivitis in herpesvirus-infected cats.” However, there has been no effect noted on herpes virus that is not ophthalmological as well as calicivirus and Chlamydophila shedding.

Besides its benefits, its intestinal de-amination forms cadaverine which has a foul smell.

On its role in dealing with the feline herpes virus, an upper respiratory disease, an initial study supported its efficacy on mild cases as it helped in reduce its shedding. This is the reason why most mainstream manufacturers still recommend its use.

Finally, some studies [1] [2] have shown that oral lysine supplementation will only worsen things and may not be helpful.

Lysine deficiency in cats

Deficiencies may be due to hereditary defects which will affect other amino acids that depend on the dibasic amino transporters in the intestine and kidney. Therefore, cysteine, arginine, ornithine will be affected since they depend on the same transporters.  Deficiency can be diagnosed by fasted plasma amino acids.

Kittens feeding on lysine-deficient diets experience weight. This amino acid is not a limiting one in feline diets and there have not been long term studies on the effect of deficiencies.

Lysine supplements for cats

If you are looking for supplements, you will get lysine powders, gels, chews (tablets), paste or liquid forms, some of the top brands to consider include the following:

  • Vetoquinol Viralys L-Lysine Supplement for Cats – For better immunity, sneezing, running nose, squinting, watery eyes in powder including Vetoquinol Viralys Gel – 1tsp has 500mg
  • Vetri Lysine Plus by VetriScience – may help in preventing FVR virus replication, support immunity, eye health, among other roles.
  • Pet Naturals of Vermont- FunShaped Chews for Cats for Immune and Respiratory Support (chicken liver flavored bites) with 250mg Lys.
  • Now Pet Health – Powder (1/8 tsp has 276mg Lys.
  • GNC Pets L-lysine– Chicken Flavor Soft Cat Chews, 250mg each.
  • Felisine supplement Paste for Cats
  • VitaPaws – 500mg sprinkle capsule
  • Now Foods – Powder form
  • Tomlyn Immune Support – Supplement Powder for Cats
  • Enisyl-F 100ml liquid solution – Available at Walmart.
  • NaturVet Lys monohydrochloride 500mg with vitamin C and astragalus root
  • Essential Pet’s 21st Century Soft Cat Chews

We will not go much into writing reviews since we will have something on lysine supplements for cats where we will review most of these brands, state their indication, dosages and much more.

Dosages will be as per the instruction of your veterinarian or their manufacturers.

Where to buy lysine for cats

If you are looking for supplements, you can get them at your various local pet stores. Ask for any of the brands we have mentioned above.

Alternatively, you can get them at the sites of the various manufacturers or online stores such as, PetSmart,, Petco, 1800PetMDs or on the respective websites of the various manufacturers.

More places to lysine for your feline friend include the following:

a). In Canada

For people who are in Canada, they can go for it at,,,,,, among other online stores.

b). In Australia

Those in Australia can look for this product at,,, among other stores

c). In the UK

Finally, if you are in the UK and you really need lysine supplements,,,,,, among many other sites have most of the brands we have mentioned.

Toxicity and lysine for cats side effects

In cats, no toxicity has been associated with this amino acid. Kittens that were given about 8 times the required amount did not show any clinical signs associated with the excess amount given.

However, we cannot conclude that a lysine for cat overdose is entirely not possible. Discuss with your vet in case of an overdose.

Finally, in puppies, it antagonizes the absorption of arginine but that has not been noted in adult cats [3]

See also

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