What Is Lysine for Cats?

Cat with Medication

Sneezing, running nose, swollen eyes, and coughing are worrying signs to any cat parent. But like humans, felines’ upper respiratory infections are common. The Feline herpesvirus type 1 (FHV-1) and Feline calicivirus (FCV) viruses cause 80 to 90% of these respiratory illnesses. Other agents, including Bordetella, feline chlamydiosis, and mycoplasma, take the remaining share. That’s why veterinary exams are necessary to help establish the best course of treatment. Often, vets prescribe medication, along with isolation, rest, proper diet, and lysine supplementation to help treat these respiratory illnesses and infections caused by FHV -1. But why do most veterinarians recommend lysine for cats?

What Is Lysine?

Lysine, also known as L-lysine, is an essential amino acid that aids in the bodily function, growth, and repair of tissue. This building block for protein (Lysine) is usually given as a supplement to felines, humans, and canines. Unlike other amino acids, your cat’s body can’t produce lysine, meaning it can only be obtained from food or supplements. This protein component supports your feline’s respiratory health and immune system. The cat’s body will need to produce the required antibodies and enzymes needed to support the immune system and facilitate calcium absorption, which is important in keeping strong and healthy bones. However, some cats don’t have sufficient quantities in their body to ward off common illnesses and infections. Lysine for cats has for a long time helped treat and manage feline herpes virus flare-ups. Many veterinarians recommend lysine supplementation as a prevention and treatment solution for kitties with upper respiratory problems or showing other symptoms of FHV-1 infections.

What You Need To Know About Lysine For Cats

Lysine for cats is a dietary amino acid supplement often administered to cats. Amino acids are essential for any animal’s body to ensure proper functioning and survival. Lysine happens to be among the essential amino acids required in a cat’s diet. Where this essential amino acid is deficient, supplementation is recommended. Generally, dietary supplements are given to help augment bodies intake of minerals, vitamins, amino acids, and other components that support fitness and proper functioning, which are not adequately obtained from the diet. However, there are many gaps regarding the sale and safety of dietary supplements. There are no stringent standards by Food and Drug Administration to govern the sale and prescription of nutritional supplements. Technically, FDA classifies all products meant to supplement diet as food products. While you don’t need a veterinary doctor’s prescription to purchase a lysine supplement, don’t go for any brand out there. Consult your veterinarian. They’ll advise you on the best quality brand, proven effective.

Why Consider Lysine For Cats?

It’s everyone’s desire to keep their pets happy and healthy. That explains why many cat owners are in the market for dietary supplements that can aid strengthen immunity and improve their cat’s health. Among the many sought nutritional supplements is lysine, as it takes a lead role in a cat’s health. It’s often administered to treat feline herpesvirus (FHV) infections. Feline herpes is a highly contagious and ubiquitous virus among cats. It’s the main cause of felines’ upper respiratory infections, and if not properly treated, it can be a lifelong infection to some cats. Boosting a cat’s immune system is the perfect way to suppress feline herpes. So, in order to fight the FHV, lysine is administered along with other prescriptions where necessary. Veterinarians will also use lysine to prevent, manage and treat a wide range of other health issues in cats such as ;

  • Sinus discharge and congestion
  • Sneezing
  • Loss of appetite
  • Conjunctivitis
  • Difficulty breathing
  • Fever blisters
  • Squinting
  • Lethargy
  • Mouth and throat sores
  • Cold sores
  • Fever
  • Panting

Poor diet, illnesses, stress, extreme temperatures, fleas, and other unpleasant conditions can weaken a cat’s immune system making the cat more vulnerable to FHV and upper respiratory infections. Similarly, even cats with strong body defense mechanisms are not immune to these illnesses. Hence, cats should take lysine regularly, whether ill or in a prime state. The long-held assumption is that lysine for cats helps prevent a wide range of the illnesses mentioned above, besides preventing the re-emergence of feline virus symptoms and any future flare-ups. Unfortunately, no specific treatment for feline herpes so far, but continuous lysine supplementation is highly recommended to help fight this cat’s contagious virus without needing a prescription.

How Does Lysine Help Cats?

Why do most veterinarians recommend lysine to help fight against the feline herpes virus common in cats? For this virus (FHV) to replicate, it will have to bind with arginine, a natural amino acid present in the cat’s body. However, lysine is meant to disrupt the binding process by accelerating the breaking down of arginine. The concept is that introducing high levels of lysine in the cat’s body stimulates the secretion of an enzyme responsible for breaking down the amino acid arginine. This helps suppress the replication of the feline herpes virus due to the low levels of arginine. As a result, the cat will feel better, and any exhibited clinical symptoms will recede. However, like any other supplement, it will take some time before lysine can produce the expected results.

Researchers Opinion About Lysine For Cats

Any touted product in the market will prompt further studies to ascertain the allegations behind it. That’s what happened to the use of lysine on cats. Various studies were conducted in the early 2000s to establish the effectiveness of lysine supplementation. However, the findings were contradictory and inconclusive. The American Veterinary Medical Association (AVMA) examined 14 FHV-1-naive young adult cats in 2003 and 261 cats in 2009, and both studies showed contradicting results. In their journal, AVMA published the results of their 2003 research showing a diminution of FHV-1 virus replication following the intake of oral dosage of lysine 400mg. However, in their 2009 journal, they claimed that lysine was not an effective tool to fight the FHV-1 virus, indicating the supplement’s likelihood of increasing the severity of the infection. Nevertheless, veterinarians highly encourage cat owners to give lysine to their felines with upper respiratory infections and feline herpes virus type 1 illnesses. But the lack of conclusive evidence of the ineffectiveness or effectiveness of Lysine continues to trigger mixed reactions among scholars. There’s been heated up debate on whether Lysine is a successful means of combating feline herpesvirus or not. Some past studies seem to disapprove of the traditional uses of Lysine, while others support the use of this amino acid. The big question is, do we have a better alternative to addressing cat’s respiratory illnesses and other associated flare-ups? Does your cat still need lysine supplementation? While some people believe that lysine can’t cure felines respiratory infections, some argue it can relieve the associated symptoms and maintain cats in their prime. How so?

Lysine For Cats: Recent Studies

Before, the veterinary community had varied views towards lysine supplementation in suppressing feline herpesvirus type 1. However, their attitude took a different twist in 2015. These researchers concluded that there was no substantial proof that lysine repressed herpesvirus replication in felines. They suggested that veterinarians should not recommend lysine for cats as there wasn’t definitive evidence in relation to its effectiveness. The key verdicts of their recent study emphasized:

  • Absence of any evidence that Lysine can mitigate FHV-1 and its unpleasant symptoms
  • Lack of proof that lysine was effective in preventing cats’ upper respiratory illnesses caused by FHV-1
  • Unjustified allegations on diminution of FHV-1 and associated symptoms in cats assigned to lysine supplement

These scholars argue that lysine is likely to increase the severity of felines respiratory illness and worsen the associated clinical symptoms. Lysine supplement is intended to lower the arginine levels, an essential amino acid in felines. On the other hand, arginine supports the functioning of the kidney, hormones, and immune system and aids in healing wounds. So, the diminution of this amino acid can threaten a cat’s life. When used on a regular basis as recommended by veterinarians, the lysine may trigger severe health issues in the particular cats taking it. In addition, cats that lack enough arginine levels are prone to hyperammonemia, a condition that can easily claim a cat’s life. In their initial studies, the same researchers believed that lowering arginine levels would help suppress the replication of FHV-I in the feline’s body, which by extension will help prevent any respiratory infections and symptoms caused by the feline herpesvirus. This formed the baseline of lysine recommendation. It was not until 2015 that veterinarians, researchers, and other concerned scholars became more cautious towards the use of Lysine for cats. However, there is no tangible proof of any severe conditions resulting from the administration of the lysine. Thus, some veterinarians still recommend its use while remaining precautious.

Lysine For Cat: Right Dosage

This dietary supplement is available in powder, gel, treat and paste forms. So, you can easily administer it by adding it to your feline’s diet. Like other supplements, you can buy lysine assigned without measure. However, it contains some substances that can be harmful to a cat if not given the right dosage. If new to the use of lysine, consult a well-informed veterinarian before you can start the cat’s lysine supplementation. Remember, different forms will have different dosage levels, meaning the quantities you administer for a powder lysine will likely differ from what will be required by the same cat in paste form. Like medication, a cat will need the correct dosage to help treat, manage, ad alleviate any FHV-1 infections and symptoms. Cat’s lysine dosage comes packaged in 250mg to 500mg, given twice or once a day. This supplement should always be tightly sealed in its original container and stored at room temperature.

Two things will influence lysine dosage:

  • The cat’s age
  • The cat’s weight

Young and less heavy cats should be given a lower dosage, while adult and heavy cats receive a higher dosage. Although it’s not always the rule of the thumb, some scenarios may require you to change the dosage levels. Consult your veterinarian for more guidance on lysine dosage for your cat. Also, adhere to manufacturers instructions as indicated on the supplement package unless your veterinarian suggests otherwise. Skipped cat lysine dosages should be given once you remember, but only if there is no lapse of several hours before the next dosage. Otherwise, skip altogether and give the next dosage at the required time.

Side Effects Of Lysine For Cats

Cats on lysine supplementation will exhibit different side effects. To some, lysine may be less damaging, while it may cause adverse effects to others. Common side effects of this dietary supplement for cats include;

  • Pale gums
  • Vomiting
  • Facial swelling
  • Nausea
  • Seizures
  • Persistent scratching
  • Diarrhea

It’s advisable to seek a veterinarian’s advice before giving lysine to a cat on other medications or supplements. That way, you can avoid unfavorable interactions that may threaten the feline’s life, like breathing difficulties, rashes, dizziness, and various digestive syndromes like ulcers or irritable bowel syndrome (IBS). That said, give your veterinarian a complete record of any medication that the cat is on.


Having a sick cat is worrying. But having a solution that can help alleviate the feline’s discomfort is promising. Now you have a deep understanding of lysine for cats, its benefits, dosage, cost, and related complications. So, you should be in a better position to determine how to keep your feline friend heath and strong. Lysine supplementation may be part of your overall approach, but ensure you stay in close consultations with your veterinarian. Err on the side of caution as it is a safer move considering the uncertainties surrounding the effectiveness of lysine.

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