What Is L-Lysine HCI Used for in Cats?

We take our lysine to avoid those nasty upper respiratory infections.
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You and your cat might take the same over-the-counter supplement, if your vet treats your kitty for certain conditions. The amino acid lysine goes by various names, including L-lysine hydrochloride. Vets use it to help felines with various ailments, as it's not only effective but has few side effects.

Feline Herpes

Many cats are exposed to the feline herpes virus and never show any symptoms. However, when exposed cats are subject to stressful situations that weaken the immune system, the virus gets an opportunity to flare up. This could result in respiratory and eye problems. Adding a small amount of lysine to your cat's food every day helps keep the herpes virus quiet, the way you want it to be. Lysine is available in pill, powder and liquid form.

Upper Respiratory Infections

Upper respiratory infections aren't that common in cats, unless the cat is around other felines with this contagious condition. It is frequently found in animal shelters, where the cats are already stressed and disease can spread fairly rapidly. Most feline URIs result from exposure to either the feline herpes virus or the calicivirus. While URIs generally run their course in two weeks or less, affected cats may spread the virus for several weeks more. Lysine might ease the symptoms of kitty's cold, as well as aid in healing mouth ulcers caused by the calicivirus.


If the conjunctiva of your cat's eye becomes inflamed, a condition often called pinkeye, your vet might advise you to supplement her with lysine. That depends on what's causing the conjunctivitis. If it's the common feline herpes virus, lysine helps stop its spread. It can also stop the symptoms, including eye discharge.


Lysine isn't just used for medical purposes. Many cat treats include it among their ingredients. An essential amino acid that the body can't produce itself, cats need to get it from food. Next time you're buying kitty treats, check the label to see if your cat's favorite brand includes lysine. If it doesn't, maybe you can switch to one that does, if Her Majesty deigns to eat them. Lysine helps to keep kitty's hair and skin in good condition. Before she turns her nose up at lysine treats, tell her they will make her even more beautiful.


If your vet doesn't sell you a specific lysine supplement made for felines but tells you to purchase an over-the-counter one, make sure to read the label. Some lysine supplements may contain propylene glycol as a preservative, which can be harmful to felines. It's also not that great for humans, so you might want to avoid it as well.

Always check with your veterinarian before changing your pet’s diet, medication, or physical activity routines. This information is not a substitute for a vet’s opinion.

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