Tuesday, October 8, 2013

What I know - Lysine

Update 4/29/16
I recently attended a session at the New England Fed conference about URI and the presenter said that in order for lysine to begin to work on the feline URI you need to supplement so heavily that it would be damaging to the cat.

Update 11/23/15
There was a study done on lysine and they believe that it has absolutely no effect on the herpes virus in cats either as a preventative or as an inhibitor, and it also found that too much lysine is actually a bad thing as I suggested it might be in this post back in 2013. As a result, my recommendations to use lysine went from 'if there is a bad flare up going on' to 'not at all'. If you want to try it to see if it helps, please do not use it for long periods of time.

If you spend any time on websites where people talk about cats, you are inevitably going to run across someone who has a kitty with upper respiratory symptoms and is wondering what can be done about them without going to a vet.

Okay, let me pause here; I am guessing some of you are here because you have a cat with upper respiratory issues and you are wondering do you need to go to a vet. Where your kitty falls on this list of symptoms will determine what you can and can not do on your own.
  • is your kitty eating
  • is your kitty active
  • does your kitty have normal output (aka litter box)
  • can your kitty breathe and see
  • is there discharge from the eyes or nose - if so is it clear or opaque or worse colored.
If you can answer the first four questions yes, then chances are you can hold off going to the vet. If the answer is no, then stop reading and call your vet. A kitty who is not eating, lethargic or is having litter box issues need to get to a vet. If your kitty can not breathe or see.. get to a vet. If there is opaque discharge, or if the discharge is red or pink or excessive get to the vet. FYI, my opinion on the matter, a vet visit is ALWAYS a good idea when your kitty is showing signs of not feeling like himself and you do not know what is causing it. You might just assume it is something when it is something completely different causing similar symptoms. AKA.. get your kitty to the vet so you can KNOW what you are dealing with.

So anyway.. often when cats sneeze and eyes are inflamed and they ask the people on the Internet for help, someone will often say "You should give Lysine, it helps boost the immune system"

This is not true.

Lysine does NOT boost a cat's immune system.

What is Lysine? Lysine is an essential amino acid. Lysine is essential to building collegian when is important for a healthy coat and skin and also aids in the absorption of calcium. Lysine is found in protein-rich foods such as meat, cheese and certain fish. It also comes in supplement form (which for the purposes of this post we are going to talk about) and available at most health food stores and some larger pharmacy sections of your local megamart.

The reason people believe that Lysine helps a cat's immune system is because it does work very well aginst one type of upper respiratory infection (URI) known as herpes and it has a history of working well in humans.

Herpes in cats is not quite the same as herpes in humans, and the virus is not zoonotic which means you can not catch herpes from your cat. Once your kitty has herpes (also known as feline viral rhinopneumonitis {FVR}, rhinotracheitis virus and feline herpesvirus type 1 {FHV-1} and is part of the "distemper" vaccine known as the FVRCP vaccine) it will most often be infected for life and it can have occasional flare ups.

Herpes is pretty common in cats and is often suspected when a cat has URI. If the kitty has a mild case it might be near indistinguishable from other forms of URI. You can do a PCR test for it, but most do not as the treatment for all standard cases of URI are generally the same and many people do not want to spend the money, so most vets do not even suggest it.

When herpes is suspected, lysine is often given. The reason to give lysine is that it inhibits the replication of the virus by taking the place of arginine - another amino acid - and that is all it does. Arginine is very important in the replication cycle of the herpes virus. Lysine and arginine are very similar in properties and if the virus uptakes lysine instead of arginine the theory is that it inhibits replication allowing the immune system do its job and not be overwhelmed with a new virus. Lysine does not kill the herpes virus, so if your kitty is in a full blown attack, it is going to take a while before the immune system fights off enough of the virus for symptoms to abate. Keeping the virus from replicating could help.

Since the herpes virus is known to remain in the body and reemerge at times of stress, lysine might play a role in keeping your kitty symptom free. If you have a history of your kitty coming down with URI after trips to the vet or when workmen come over etc, supplementing with lysine prior to the stressful event might ward off symptoms.

Humans with the herpes virus use lysine to help with symptoms. Doctors generally tell their patients to eat a diet rich in lysine and avoid arginine rich foods. There is little known about the risk of long-term supplementation in cats. In humans, the short-term side effects can include stomach pain and diarrhea which can also occur in your feline. Because of lysine's ability to increase absorption of calcium, you need to be aware of hypocalcemia. In humans, there are issues with high cholesterol and gallstones. There have even been reports of kidney issues. Are these risks translatable to felines? We do not know. No one has funded the studies to see what the long-term side effects in cats are. While a lot of health risks and benefits do not translate from human to feline, many do. It is good to be aware of what it has done in humans and if you have a kitty with kidney issues or an issue with hypocalcemia that you discuss if supplementation is a good idea for your kitty.

There is no known benefit to giving lysine to a cat who does not suffer from the herpes virus. Since there are possible side effects to giving it, I feel that we should use it with some caution. If you have a cat with URI symptoms, giving a supplement of lysine short term, up to a couple of months might help. If you see improvement, keep it on hand if your kitty has another outbreak. If you do not see improvement, you might want to take your kitty back to the vet for further testing. Investing in proper tests will help ensure that you are treating the kitty for the issue it has and in the long run, can be less expensive and less frustrating for both you and the cat.

If you choose to supplement your kitty with lysine, there are many cat-friendly lysine "treats" you can purchase to make getting it into the kitty simple. I am not a fan of most of those due to the nonactive ingredients in them. You can purchase capsules of lysine powder at most stores that sell supplements and open them up and sprinkle it right on your cat's regular food. Most cats do not show any signs of noticing when the lysine is added. The recommended dose varies quite a bit, with 250-500mg being suggested as a starting dose for adult cats with some people going up to as high as 1500mg. Splitting the dose throughout the day is more beneficial than giving it just once a day. Kittens should be started at lower doses by half. Eyeballing the dose is perfectly acceptable, so if you buy 500mg capsules, giving 1/4th of it to a kitten per meal should be fine.

Jack being contemplative..
Not really anything to do with this post other than I'm discussing medical issues:
Again, what seemed to be a rational approach resulted in harm. There are aspects to human biology and human physiology that you just can't predict. Deductive reasoning doesn't work for every case. Sherlock Holmes is a model detective but human biology is not a theft or a murder where all the clues add up neatly. Rather in medicine there is an uncertainty that makes action against a presumed culprit misguided. How Doctors Think by Jerome Groopman

I have been listening to this audio book and have found it very fascinating. This quote (possibly very poorly punctuated) really hit home for me when thinking about medical choices I have to make for myself and my cats. I have been saying something like this for quite a while now when people spout 'calories in vs calories out' in weight loss.. the human body is not a mathematical equation. Basically, where I'm going with this is I am not a vet. I do not play one on the Internet. All information is an aggregate of what I have found in reading and trying to understand what might help my cats, with a smattering of what has helped my own cats. Just because these things worked for my cats or their cats, does not mean it will work for your cat. Medicine is a science, yes, but it is also very much an art.

Additional reading:

Lysine for Feline Herpesvirus: Does it Help?


  1. This is a good article, thanks. You chimed in about this a while back on FB, and it's great to have all of this information together in one place so I can point to it.

  2. Well, cr*p. I've been giving the boys the Lysine treats daily for oh, ages now. A couple of years? Maybe not quite that long. Derry used to have a watery eye all winter long, but didn't last winter, and I assumed the Lysine was helping.

    But maybe I'm making my cats sicker. Maybe they're going to die in middle-age because I thought I was doing something helpful. Ugh. One more thing I'm going to be paranoid about now!

  3. THANKS!! I know we were just talking about this and this lines it all up in my head.

    I have to agree - vet first. dr google should not be anyone's main source of medical care for themselves or anyone in their family.

    as for us.....Jake looks good, Elwood looks better, and now Oliver's eyes are runny again. sigh.

  4. Thank you, as always, for the information. I've read a lot about lysine for human use but not feline.

  5. Very good information and background on Lysine, thank you for putting this all together. It was very helpful.

  6. Thanks for the post! One of my cats has herpes, and the vet recommended lysine. The cat would not eat food with the powder mixed in, and he even turned up his nose at the lysine treats, so now I buy the gel. He won't eat it mixed into his food (*sigh*), but he will lick it off my finger. Picky!

    One of the rescues I volunteer for lysines all cats in care, which to me is silly. If it ain't broke, don't fix it, no?

    p.s. You can buy lysine gel on ebay for half of what a vet will charge you.

    1. Anonymous6:56 AM

      I know this is very old but just wanted to note that my Foster has a building where the kitties live, and in the winter we see an increase in upper respiratory infections except when we start using lysine in late fall, until spring

      So. That's one reason we treat everyone:)

    2. You really shouldn't. The evidence against lysine only increases. In general, it is basically a waste of money but if you use too much it can be harmful

  7. RE: Fuzzy Tales

    If your kitty isn't having an issue then you aren't making them sicker. If the lysine is keeping the watery eye at bay then it is helping. Do you need to give them year round? I don't know. There are cats that are on them year round because they flair up so often. The post's intention was to dispel the myth that lysine helps immunity and there are no side effects so there is no reason why you shouldn't give it. You have a reason.

  8. Thank you for the information! I didn't know much about lysine but glad I learned about it!

  9. I've not had to use Lysine on anyone and hopefully won't need to. I'm not very well versed with it so this post is very helpful. Thanks for putting it together!

  10. Fuzzy Tales,

    Watery eye/eye infections can be a Herpes thing and, therefore, Lysine could be helping. Every foster that I've ever had that was prescribed Lysine had eye issues. It helped some, made no difference in others. If it helps Derry, then talk to your vet about keeping him on it.

  11. I agree, that was super information and you pulled it all together nicely!

  12. Wonderful info
    Thanks much
    I was wondering if you would be so kind as to drop me a line on how much a kitten of 4-5 week should be given in formula? I just took in a very sick little one from a friend who saved her off her porch. She was cold and when warmed started to show life and is taking small amounts.
    Thanks much in advance

    Timmys Dad Pete

    cusackpete at gmail dot com

  13. Good information. I've never used lysine with my cats. But I know others have. So this is good info.

  14. Great post! I definitely know where to go if lysine ever comes up. Yes, making medical decisions, especially for my kitties, is difficult and I always take what I read on the Internet with a huge grain salt.

  15. This is excellent advice and I learned a lot. Cats are so good at hiding what ails them, its easy to miss something subtle, so its best to visit the vet.

    So many popular notions have been de-bunked, even taking lots of vitamin C when one has a cold. Personally I feel if ones eats a balanced diet, you don't need supplements. That goes for kitties too.

    When my mom was diagnosed with terminal leukemia, the specialists at Johns Hopkins told her to stop taking supplements. They all said there have been many studies showing they do more harm than good.

  16. Nice article. As a cat guardian with FHV, lysine is such a godsend. He used to need antibiotics so often I used to wait until he got really bad so we didn't overdo the antibiotics. Since lysine, he has needed antibiotics once in 3 years!

    1. My 9 yr old Burmese girl has been having herpes flare-ups since being on steroids for skin disease. After the first one when she nearly died of pneumonia I started using lysine every time she had a steroid injection at a dose of 500mg every 12 hrs for just over 10 days. Having to balance another bout of pneumonia with lung damage against possible kidney problems, I had no choice,but I think more than the above dose caused digestive problems.

  17. I think this is great info and advice. I don't know many people who actually test their cats for the Herpes virus when it's suspected. The Feline Upper Respiratory panel was one of the most expensive tests I remember running. I guess a doctor can make a pretty educated guess, but without a test it's still just a guess.

  18. great information Connie,I didn't know any of this,thanks,xx

  19. This is a very useful article. From what we see on FB, we thought Lysine was a miracle drug for everything sort of like coconut oil, which I won't lick.

  20. Thank you so very much, it was a very interesting post.

    I agree that all cats (and humans) are different and the treatments for some might not be the best for others. That is why I think the Internet can be such a gem for the people who actually do research and track sources: we can read about experienced people, like you, and take a decision relying on several testimonies and experiences, in addition to the doctor/vet's input of course, just not blindly trust that one single source is the only one that must be true.

    (Texas' human)

  21. Anonymous2:05 PM

    Thank you so much for the info!

  22. has there been any links with a lisinr to dental problems yellowing of teetg,bad breath and irritated gums.

  23. Anonymous10:30 PM

    Well said....thanks for posting this and getting the word out.


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