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10 Best Lysine Supplements for Cats in 2021 – Reviews & Top Picks

cat having treat

Lysine is often used to treat symptoms commonly caused by feline herpes virus infections. If your cat is diagnosed with this condition, your vet may prescribe or recommend a lysine supplement.

If this is the case for your cat, there are many options for you to choose from. Many of these are high quality but differ slightly in the formulation. It’s important to remember that lysine supplements aren’t regulated in the United States, so it’s essential to do your research before making a purchase.

Here, we created reviews of 10 of the best lysine supplements on the market. One of these should be suitable for your feline!

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A Quick Comparison of Our Favorites

Image Product Details
Best Overall
Winner
Strawfield Pets L-Lysine Immune Support Cat Supplement Strawfield Pets L-Lysine Immune Support Cat Supplement
  • Feature iconDesigned for immune support
  • Feature iconNatural chicken flavor
  • Feature iconPowdered
  • Best Value
    Second place
    21st Century Essential Pet L-Lysine Cat Supplement 21st Century Essential Pet L-Lysine Cat Supplement
  • Feature iconChicken flavor
  • Feature iconHuman-grade ingredients
  • Feature iconLess expensive
  • Premium Choice
    Third place
    Thomas Labs Felo Lysine Powdered Cat Supplement Thomas Labs Felo Lysine Powdered Cat Supplement
  • Feature iconAntioxidants included
  • Feature iconEasy to administer
  • Feature iconNo added flavoring
  • PetHonesty Lysine Immune Health+ Supplement for Cats PetHonesty Lysine Immune Health+ Supplement for Cats
  • Feature iconMade in the U.S.A.
  • Feature iconTaste yummy
  • Feature iconMade with chicken, tuna, and catnip
  • VetriScience Lysine Plus Chicken Liver Immune Supplement for Cats VetriScience Lysine Plus Chicken Liver Immune Supplement for Cats
  • Feature iconDMG included
  • Feature iconIncludes collagen
  • Feature iconBite-sized chewable
  • The 10 Best Lysine Supplements

    1. Strawfield Pets L-Lysine Immune Support Cat Supplement — Best Overall

    Strawfield Pets L-Lysine Immune Support Cat Supplement

    Dosage 900 mg

    The Strawfield Pets L-Lysine Immune Support Cat Supplement is the best overall lysine supplement for cats. It is designed to support your feline’s immune system, which can be helpful for those with feline herpes and other immune issues. It may also be suitable for older cats because their immune system sometimes declines with age.

    This powdered supplement is easy to use. You can use it to treat a variety of different symptoms, including coughing, sneezing, runny nose, and congestion. It may also treat upper respiratory infections, especially in older felines.

    The natural chicken flavor covers up the taste of the supplement. Most cats won’t have a hard time eating this, which is one reason that we recommend it so highly. You only need to use one scoop daily, no matter your cat’s size. Just mix it in at mealtime.

    Pros
    • Designed for immune support
    • Natural chicken flavor
    • Powdered
    • Simple instructions
    Cons
    • Difficult to mix with certain foods
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    2. 21st Century Essential Pet L-Lysine Cat Supplement — Best Value

    l Pet L-Lysine Amino Acid Support Soft Chews Cat Supplement

    Dosage 125 mg

    If you’re looking for a cheap option, you may want to consider the 21st Century Essential Pet L-Lysine Cat Supplement. It is the best lysine supplement for cats for the money. It’s designed specifically to support your cat’s immune and respiratory systems.

    While this supplement is less expensive than some other options, it is made with human-grade ingredients. It also has a chicken flavor to make these chews easier to feed your feline.

    That said, while they are tasty for some cats, they are less appealing to others. Therefore, you may or may not be able to effectively give this supplement to your cat. It depends on their preferences.

    Still, the dosage is lower than that of some other supplements, which may be why it is less expensive. Therefore, you may have to feed more of it to your feline for the same results.

    Pros
    • Chicken flavor
    • Human-grade ingredients
    • Less expensive
    • Chews
    Cons
    • Lower dosage
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    3. Thomas Labs Felo Lysine Powdered Cat Supplement — Premium Choice

    Thomas Labs Felo Lysine Powder Cat Supplement

    Dosage 300 mg

    For those who have extra money to spend, Thomas Labs Felo Lysine Powdered Cat Supplement seems to be a bit more effective than some other options on the market, though it is also more expensive.

    This supplement includes lysine and antioxidants, which also help improve your cat’s immune system. The antioxidants can reduce free radicals, which are the cause of many different conditions. Therefore, they are effective for older or sickly cats that need all the help that they can get.

    As a powder, this supplement is easy to administer. You can mix it in with your cat’s food, though it does work best in wet food.

    That said, this supplement does require a large scoop size, so you’ll go through it quickly. That makes this supplement even more expensive because you have to purchase it more often.

    Pros
    • Powder
    • Antioxidants included
    • Easy to administer
    • No added flavoring
    Cons
    • Large scoop size
    • Expensive
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    4. PetHonesty Lysine Immune Health+ Supplement for Cats

    PetHonesty Lysine Immune Health+ Tuna & Chicken Flavored Powder Immune Supplement for Cats

    Dosage 500 mg

    The PetHonesty Lysine Immune Health+ Supplement for Cats is similar to most other options on the market. It is created with catnip, chicken, and tuna. Most cats love these flavors and have no problem eating this supplement. You can mix it with their food or feed it to them directly. Many people reported that their cats lick up the supplement directly, without needing to add it with anything.

    This supplement is made in the U.S.A. — most other supplements on the market are made in China. This supplement doesn’t contain any wheat, corn, soy, or preservatives.

    You only need to provide your feline with one to two scoops per day to support their overall immune system. It can aid in treating all sorts of conditions because it has immune-supportive properties.

    Pros
    • Made in the U.S.A.
    • Taste yummy
    • Made with chicken, tuna, and catnip
    Cons
    • Powder is sometimes difficult to use
    • Not as full spectrum as other options
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    5. VetriScience Lysine Plus Chicken Liver Immune Supplement for Cats

    VetriScience Vetri-Lysine Plus Chicken Liver Flavored Soft Chews Immune Supplement for Cats

    Dosage 250 mg

    Overall, the VetriScience Lysine Plus Chicken Liver Immune Supplement for Cats is designed to support your cat’s respiratory and immune system by including a variety of different ingredients. Lysine is the primary ingredient, but it also includes DMG and collagen.

    That said, this supplement only has 250 mg of lysine per dose. This is much lower than some other options, so it may not work well for cats that need a particularly high dosage.

    These chews are bite-sized and designed to be quite tasty. However, since they are chewy, the whole dosing process requires that your cat likes them. If they don’t, you’re out of luck and will need to choose a different supplement.

    Hiding this supplement in food is difficult. You can crush the chews into a powder, but this seems like an extra step when you could just purchase a powder supplement to begin with.

    Pros
    • DMG included
    • Includes collagen
    • Bite-sized chewable
    Cons
    • Not all cats like the flavor
    • Difficult to hide in food
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    6. Vetoquinol Enisyl-F Lysine Bites Supplement for Cats

    Vetoquinol Enisyl-F Lysine Bites Chicken & Liver Flavored Soft Chews Immune Supplement for Cats

    Dosage 500 mg

    Since it is in the form of a small chew, the Vetoquinol Enisyl-F Lysine Bites Supplement for Cats is designed to be quite tasty and palatable. After all, the only way that you can administer it to your cat is if it is eaten freely.

    These treats are made in the U.S.A. and manufactured according to strict standards.

    However, these chews are hard and not palatable to many felines. Also, they are quite expensive if you follow the recommended dosage instructions.

    If these chews don’t work for your feline, this company also makes a variety of other lysine supplements. For instance, one is in the form of a paste that you can apply to your cat’s paws or mix with food.

    Pros
    • Made in the U.S.A.
    • Designed to be tasty
    • Manufactured according to pharmaceutical standards
    Cons
    • Too crunchy
    • Expensive
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    7. NOW Pets L-Lysine Cat Supplement

    NOW Pets L-Lysine Immune System Support Cat Supplement

    Dosage 276 mg

    The NOW Pets L-Lysine Cat Supplement is a good budget option. It is quite cheap, and the dosage is so small that one bottle lasts a long time.

    The powder is designed to be mixed with food, enabling you to easily administer it to your feline. However, most cats won’t simply lick up the powder, as it isn’t tasty by itself. You can mix it with dry food, though it works best with wet food. Since it isn’t strongly flavored, it’s easy to hide in most foods.

    This supplement is certified by the National Animal Supplement Council, so it does have a bit more authority than some others on the market.

    That said, many cats find this supplement less than appealing. Sometimes, they won’t eat their food if this supplement is added. However, this supplement does seem to work when they do try it. The dosage is a bit low, though, so you’ll need to consider your cat’s exact dosage needs before purchasing this supplement.

    Pros
    • Easily mixes with food
    • Inexpensive
    • Certified by the National Animal Supplement Council
    Cons
    • Some cats refuse this tasteless powder
    • Low dosage
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    8. Zesty Paws Core Elements Lysine Supplement for Cats

    Zesty Paws Core Elements Lysine Immune Salmon Flavored Soft Chews Allergy & Immune Supplement for Cats

    Dosage 500 mg

    The Zesty Paws Core Elements Lysine Supplement for Cats is designed to be an overall immune-supporting supplement for your cats. Lysine is the main ingredient at 500 mg. However, there are various other ingredients. For instance, astragalus root powder is present, which is advertised to support your feline’s immune system.

    This formula is completely free from corn, wheat, and soy. It also doesn’t contain any artificial flavorings or preservatives. It is made in the U.S.A., which means it has to adhere to decently high standards.

    That said, there are many reports of felines not eating these treats. They just don’t seem to be that tasty. If your cat won’t eat them, there isn’t much good that these supplements can do, even if they do have great ingredients.

    The treats are also quite large, which turns off many cats.

    Pros
    • Free from corn, wheat, and soy
    • Made in the U.S.A.
    • Contains 500 mg of lysine
    Cons
    • Large
    • Not that tasty
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    9. Under the Weather L-Lysine Cat Supplement

    Under the Weather L-Lysine Soft Chews Cat Supplement

    Dosage 250 mg

    Under the Weather L-Lysine Cat Supplement doesn’t include any corn, artificial flavors, or dyes. It’s made in the United States — in Vermont, specifically. Therefore, it is held to high manufacturing standards.

    These chews have a fish flavor. Since they are chews, it’s essential that they taste good.

    That said, there are many reports of cats not liking this supplement. If your cat doesn’t eat them voluntarily, there isn’t much you can do about it. Crushing them up may work, but that is simply extra steps on your part.

    Furthermore, these chews are not soft at all. They are extremely hard, which makes them even more difficult for many cats to eat.

    Pros
    • Free from corn, artificial flavors, and dyes
    • Made in the U.S.A.
    • Whitefish flavor
    Cons
    • Not soft
    • Not tasty
    • Low dosage
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    10. Four Paws Healthy Promise L-Lysine Cat Supplement

    Four Paws Healthy Promise L-Lysine Cat Supplement

    Dosage No Specified

    For the most part, Four Paws Healthy Promise L-Lysine Cat Supplement is like many other supplements out there. It has lysine and a variety of other helpful supplements. For instance, salmon oil is included. While this may not be an obviously immune-supporting ingredient, it can support your feline’s coat and skin.

    These chews have a chicken flavor. However, they are not nearly as tasty as some other options. Cats seem quite ready to refuse these treats.

    This supplement is made in the U.S.A, but the ingredients come from around the globe.

    One of the worst things about this supplement is that it doesn’t specify the amount of lysine included. It does provide a percentage, but that doesn’t tell you much. No milligram dosage is provided, which makes it hard to compare it to other supplements or trust the manufacturer.

    Pros
    • Made in the U.S.A.
    • Many ingredients for overall health
    Cons
    • No dosage provided
    • Ingredients from “around the globe”
    • Not that tasty

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    Buyer’s Guide

    Getting the right lysine supplement is essential for your cat’s overall wellbeing. If you purchase the wrong supplement, your cat may not get better. Therefore, you should do plenty of research before diving in and choosing a particular supplement.

    Here, we go over everything that you need to consider when purchasing a lysine supplement for your feline friend.

    Dosage

    You might be surprised by the range of lysine doses offered on the market. Some supplements have as little as 200 mg of lysine, while others have well over 700 mg. Therefore, choosing one that is closest to the amount that your cat needs is highly recommended.

    You can also choose to dose the supplement independently. For instance, if a supplement contains 200 mg of lysine and calls for one chew a day, you can simply feed your cat two a day if they need 400 mg.

    To find out how much lysine your cat may benefit from, talk to your vet. It depends on many factors, including your cat’s size and the underlying condition that you’re trying to treat.

    himalayan cat eating treat
    Image Credit: Piqsels

    Powder vs. Chew

    You can purchase lysine as both a powder and a chew. It appears that chews are the most common.

    The main benefit of a chew is that you can give it to your cat like a treat. However, most lysine chews aren’t the tastiest, so many cats may not eat them at all. If your cat won’t eat a chew like a treat, you’re pretty much out of luck.

    Hiding them in other foods is often difficult. Sometimes, you can crush chews up into a powder to hide them easier. But at that point, you might as well just purchase a powder.

    Different chews come in different sizes. Some cats are perfectly fine with large treats, but others prefer small treats. If the treat is too big or too small, they may refuse to eat it.

    Powders are made to be put into your cat’s food. Sometimes, though, they’re so tasty that cats will eat them straight. These supplements work best with wet food, but they can be mixed with dry food too. You just might end up with some of the powder at the bottom of the bowl and wasted at the end of each mealtime.

    Furthermore, some cats may not eat their food if it contains powder. However, you can hide it in other foods, such as tuna or broth.

    Which option you choose mostly depends on your cat’s preferences. You may have to try both before you find an option that your cat will take. You may need to have your picky cat try many different options before you figure out one that they like.

    calico cat having treats
    Image Credit: Andriy Blokhin, Shutterstock

    What Is Lysine Used For?

    Lysine is mostly used to treat the feline herpes infection in cats. This supplement also seems to improve a cat’s immune system, which theoretically makes it useful for treating just about anything.

    It may be particularly helpful for a feline that already has a compromised immune system. For instance, it can be given to older cats that are constantly getting minor illnesses. Some kittens may also benefit from this supplement because they often have weaker immune systems than adults.

    If your cat is prone to infections, this supplement may help prevent them. Generally, these supplements are advertised to treat a wide variety of different things.

    That said, there is little clinical data to back up the effectiveness of this supplement. Therefore, this supplement may or may not work as effectively as you’d like. However, it does have minimal side effects, so many vets recommend giving it a try.

    Since this is a short-acting supplement, the effects disappear if you stop giving it. Therefore, many cats must continue to take it for the rest of their life.

    Price

    In many cases, lysine supplements aren’t that expensive. You can get most supplement products for under $20. However, since this is a medication, you do have to be careful about the cost. Some supplements will be inexpensive but have a fairly low dosage, so you’ll have to give your cat more for it to have an effect.

    Sometimes, it’s cheaper to purchase a more expensive medication with a higher dosage. Regardless, be sure to check the products’ dosages and compare the prices accordingly. If you look at the price tags alone, you could end up spending more in the long run.

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    Conclusion

    In many cases, cats will benefit from Strawfield Pets L-Lysine Immune Support Cat Supplement. This powdered supplement is extremely easy to administer and is quite potent, so you don’t have to use too much.

    For those on a budget, you may want to consider purchasing the 21st Century Essential Pet L-Lysine Cat Supplement. It’s far less expensive than most others on the market. However, the potency is quite low, so you’ll need to keep your cat’s needs in mind before purchasing.

    For those who would like the best of the best, we recommend the Thomas Labs Felo Lysine Powdered Cat Supplement. It’s expensive but has a variety of different ingredients that may be helpful for your feline.

    We hope that you can use our reviews to choose the best lysine supplement for your feline and that it helps your cat’s overall health.

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    Featured Image Credit: Svyatoslav Balan, Shutterstock