Lysine for Cats – What You NEED to Know

Published by Jaclyn

Updated on

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What is the Role of Lysine for Cats?

Amino acids in any animal body are essential for the body to survive. They take part in almost every bodily function. Lysine is an essential amino acid that helps produce antibodies and aids in calcium absorption. This is important, so our kitties can fight diseases and have healthy bones. Cats do not make lysine on their own. They must obtain it through their food and supplements. 

Kitten, Lysine for Cats - What You Need to Know - I Love Veterinary

What are the Benefits of Using Lysine for Cats?

Lysine is mainly used to fight the feline herpes virus (FHV-1) in cats. In order for FHV-1 to replicate, it needs to bind with the amino acid arginine. Lysine works by interrupting that relationship, therefore making it less likely for the virus to worsen, and will show a diminution in the clinical signs. 

Veterinarians can also use lysine to help treat clinical signs associated with other upper respiratory diseases. It’s common for kittens to come down with the virus, and because their immune system is not as developed, it makes it harder for them to fight. This leaves them with discharge from their eyes, and nose making them super uncomfortable. Lysine will help lessen the discharge and give the kitten’s immune system a chance to fight. 

Unpacking the Feline Herpesvirus

In order to understand the importance of lysine and its benefits, you must first understand Feline Herpesvirus (FHV-1). FHV-1 is comparable to the common cold in humans. It shows up through nasal discharge, conjunctivitis, and other upper respiratory ailments. FHV-1 is extremely common, and it is likely that most cats have been exposed to it at some point. Some just have better immune systems to fight it and rarely show signs. Others can get severe cases and have secondary infections occur. Below is a list of typical clinical signs of FHV-1:

  • Coughing
  • Sneezing
  • Runny nose/ productive discharge
  • Conjunctivitis
  • Lethargy
  • Inappetance
  • Squinting of eyes
  • Wheezing
Cat sneezing, Lysine for Cats - What You Need to Know - I Love Veterinary

It’s important to consider your cat’s overall health when choosing to treat FHV-1. You should always let your veterinarian know of any clinical signs, so they have a proper history and are aware of any future flare-ups. 

FHV-1 is likely to flare up when cats’ immune systems are weakened through concurrent diseases or stress. It is also common for cats to develop secondary infections because their immune system is not in tip-top shape and has trouble fighting any foreign pathogens. In these cases, cats can be given anti-virals, antibiotics, along with lysine to help fight the diseases taking over. 

What is the Correct Dosage for Lysine?

Lysine comes in many forms. It can be a powder, a treat, a gel, or a paste. It’s important to note that this is a dietary supplement, meaning that it is added to your pet’s food/ diet and can usually be found over the counter. 

However, it does contain substances that can be harmful to your pet if used inappropriately. Therefore (this goes for any medication or supplement), it is always best to consult with your veterinarian before giving. Many times they can suggest a dose that is different than what the bottle suggests. Their dose is more appropriate to manage your cat’s clinical signs. 

What are the Side Effects of Lysine

The side effects of lysine are rarely seen; however, no medication or supplement is without them. By using lysine, you are blocking the amino acid arginine. Without this amino acid, cellular and organ function can be disrupted. 

It has also been noted that lysine can cause allergic reactions and can stay in the system longer for any cats with kidney or liver disease. It has also been reported that it may cause diarrhea

Chemical formula for Lysine with pills, Lysine for Cats - What You Need to Know - I Love Veterinary

Lysine FAQ’s

Q: How often do you give Lysine?

A: Lysine is an oral supplement. Regardless of its form {pill (crushed or whole), powder, gel, or paste}, it should be given with food. It may take up to a few weeks to see its benefits. 

Q: Are there any drug interactions to be aware of when giving my cat Lysine?

A: Always give a complete list of current medications your cat is on. This will help decrease any chance for drug interaction and educate you on their signs. Drugs that are used to supplement calcium or arginine should be avoided. 

Q: Are there any risk factors when giving Lysine?

A: There aren’t many known risk factors when giving your cat this supplement. Always use with caution in pregnancy or nursing queens. It’s always best to consult your veterinarian before using the supplement for any possible personal risk factors. 

Q: Does my cat need to be monitored while taking this medication?

A: This medication is supplemental and considered to be over the counter. That being said, your cat does not need to have their blood work monitored for refills. It is wise though, to check in with your veterinarian to ensure it is working correctly.

Q: How is Lysine stored?

A: Always consult the package or bottle for specific storage instructions. However, it is usually stored in an airtight container at room temperature. 

Q: What if I miss a dose?

A: If the dose you missed is far enough away from the next dose then it may be given. If it’s in close proximity, then it’s best just to skip that dose. Consulting with your veterinarian is always a safe idea when it comes to missing doses. You want to avoid double-dosing your cat because that can lead to adverse side effects.

Q: Can I give my cat a human form of Lysine?

A: There is no evidence supported or limited amounts that state it is safe to use human lysine for cats. Make sure to use a supplement that is safe and dosed appropriately for cats. 

Cat sniffing dry catnip, Lysine for Cats - What You Need to Know - I Love Veterinary

What are the Alternative Solutions to Lysine?

There are a few alternative solutions that can be put into place instead of using a supplement. Of course, you can do all of the below suggestions while also  the supplement:

  • Calm environment– make a safe and calming environment to avoid stress in your kitty. Adding catnip or pheromones to your cat’s environment can help aid in de-stressing them. 
  • Foods with lysine– giving foods that are rich in lysine or making sure you incorporate all of your cat’s essential amino acids and vitamins will help keep your cat healthy. 
  • Probiotics– probiotics help to maintain a healthy gut in your cat. 
  • Antivirals and antibiotics- these are used in extreme cases and if any secondary infection is present. 


It’s never fun to see your feline friend sick. So having something on hand that can help them is comforting. Knowing all the risks and information that is involved when giving lysine is important. Staying in touch with your veterinarian on your cat’s current health status along with providing supplements and medication will aid in great health care.

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Jaclyn is a Licensed Veterinary Technician (LVT) who has a bachelors degree in journalism. Combining her two interests of writing, and veterinary medicine is a true passion. Jaclyn has already created her own blog called The Four Legged Nurse. She is blessed with two children, a wonderful husband, and four devoted fur babies. In her free time she loves spending time with her family, reading, and riding horses.


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