NOW Pets L-Lysine Immune System Support Cat Supplement, 8-oz jar

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At a Glance

  • Gluten Free
  • Immune Support
  • Eye Care
  • All Lifestages
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About This Item

Details

  • This powder supplement for cats features L-lysine to support a healthy immune system, normal respiratory health, and ocular health.
  • Crafted with 100% L-lysine powder that’s pure, pet-safe, and free from fillers.
  • This supplement is certified by the National Animal Supplement Council (NASC).
  • NOW makes their pet supplements with the same attention to quality and detail they put into their human products, giving pet parents peace of mind.
  • Packaged in the USA by a family-owned and -operated company since 1968.

Ingredient Information

Instructions

FAQ

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Questions & Answers

19 Customer Questions

Will this harm my cats if I feed it to them more then two times a week?

Answer by Chewy • Mar 19, 2022
Results from two clinical trials with cats suggest that excess dietary lysine may have an enhancing effect on FHV-1 replication, so some caution is suggested in supplementing. This newer evidence recently led NOW Pets' veterinarian formulator to recommend lowering the serving frequency, which they changed on their label over 8 months ago. One suggestion would be to pick specific days - for example, Wednesday and Sunday - to add the supplement. If you have any further questions please discuss with your vet.

How many servings does this jar have?

Answer by Chewy • Sep 10, 2022
NOW L-Lysine for Cats has a varying number of servings, depending upon weight. For cats up to 5 3/4 pounds, give 1/16 teaspoon twice weekly. For cats over 6 pounds, give 1/8 teaspoon twice weekly. Using a 1/8 tsp (276 MG) serving, divided into the total weight of 226.8g = 821 servings. If giving to a smaller cat (1/16 tsp) it would have twice as many servings. If using for one cat, twice weekly, as suggested, one bottle would last for years.

How long until l-lysine starts to suppress and alleviate any symptoms a cat may be experiencing?

Answer by Chewy • Jun 11, 2020
NOW Pets L-Lysine Immune System Support Cat Supplement supports a healthy immune system. There is no time frame in supporting the immune system.

Can you put the powder on dry food?

Answer by Chewy • Mar 24, 2018
This supplement should be administered during or after the animal has eaten to reduce the incidence of gastrointestinal upset. It can be added to their dry or wet food.
Reviews
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4.5
Rated 4.5 out of 5 stars
519 Ratings
Terms & Conditions

Customers Mention

Chewy identifies key considerations with the help of artificial intelligence and our veterinarians.

Effectiveness

81% Positive

Form and Administration

84% Positive

Ingredients

86% Positive

Nutritional Value

87% Positive

235 Customer Reviews

Rated 5 out of 5 stars
By MissRonnie on Jan 11, 2026
Top 500 Contributor

Not sure of results

Well, the only thing that I can say about this product is that I purchased it because one of the feral cats coughs periodically. Not sure about the results, but

Well, the only thing that I can say about this product is that I purchased it because one of the feral cats coughs periodically. Not sure about the results, but will continue to use this product.

Rated 5 out of 5 stars
By Holly on Oct 13, 2025

Finally! One they would take!

I have tried the chews and turkey flavored drops, chews being a massive failure for both our kitten and grown kitty, drops only being accepted by the kitten slightly

I have tried the chews and turkey flavored drops, chews being a massive failure for both our kitten and grown kitty, drops only being accepted by the kitten slightly when mixed. But I sprinkled this in their food and neither could tell it was there. My older cat licked it right off the mixing spoon. I would give a 10 if it was designed to give more frequent like the others, but 3rd try was a charm. Don’t waste your money and time attempting to get them to take the others, it sucks feeling like a failure especially when you are trying to help your sick babies I 110percent recommend buying this one first and foremost.

Rated 5 out of 5 stars
By Lynn on Nov 23, 2025

I love the convenience

I've been using this product for several years now. I use it as a supplement for all my cats, but especially for two that seem to have seasonal sensitivity. Easily

I've been using this product for several years now. I use it as a supplement for all my cats, but especially for two that seem to have seasonal sensitivity. Easily added to their everyday diet.

Rated 2 out of 5 stars
By Melinda on Oct 5, 2025

Dose or concentration too low?

Switched back to Viralys which he was on for months, and had brought his feline herpes virus symptoms under control. I switched to this due to the price difference,

Switched back to Viralys which he was on for months, and had brought his feline herpes virus symptoms under control. I switched to this due to the price difference, but using the dosing instructions on the bottle, his symptoms returned in full force after two weeks. It also seems to be a lower concentration. 1/8 tsp viralys is about 600 mg (given twice daily), but 1/8 tsp of this is only about 276 mg (given twice weekly).

Rated 4 out of 5 stars
By Stephanie on Oct 17, 2025

Seems to help

I have several cats both indoors and outdoors. Viruses used to bounce from cat to cat but since using this I've noticed a huge decrease in symptoms. There is no

I have several cats both indoors and outdoors. Viruses used to bounce from cat to cat but since using this I've noticed a huge decrease in symptoms. There is no measuring scoop though. I'm glad that I kept one from another product.

Rated 5 out of 5 stars
By Dian on Aug 19, 2025

Great for Skin Health

My kitty can get itchy at times- it used to be a ongoing battle and for a while we considered if she had a food allergy. But what seemed to really do the treat was

My kitty can get itchy at times- it used to be a ongoing battle and for a while we considered if she had a food allergy. But what seemed to really do the treat was a combination of more Omegas and L-Lysine. I can tell the difference when I don't give it to her after a few weeks (more itchy, eyes a bit dull). My cat is veeery picky and smart with any change in her food so I have to dissolve this in a bit of water and then mix it into her wet treats- I put a squirt of fish oil in this as well and put it on a plate, she laps it up with only slight Suspicion. Been doing this for years. L-Lysine treats work too, but my girl again is picky and hates the texture of those on the market

Rated 1 out of 5 stars
By Tim on Dec 2, 2025

Seeaira will still not eat this version either.

Moxey will eat anything, Seeaira won't touch anything it's in. Worried about "overdose" for Moxey and not helping Seeaira at all.

Moxey will eat anything, Seeaira won't touch anything it's in. Worried about "overdose" for Moxey and not helping Seeaira at all.

Rated 5 out of 5 stars
By Wanda on Oct 18, 2025

Good for my cats.

I have a cat with severe allergies and I have been to several vets for help and other than antibiotics and steroids them is is the only thing that keeps her as healthy

I have a cat with severe allergies and I have been to several vets for help and other than antibiotics and steroids them is is the only thing that keeps her as healthy as I can between her episodes of illness.

Rated 5 out of 5 stars
By Sue on Dec 22, 2025

Convenience

Tried the gel but they didn't like it. Put powder in the food they didn't even notice.

Tried the gel but they didn't like it. Put powder in the food they didn't even notice.

Rated 5 out of 5 stars
By Crazy Cat Lady on Oct 17, 2025

Easy to mix with food

My cat has chronic nasal issues. And she doesn't tolerate taking medication. I started using this about a month ago. I put it in her wet food and she eats it

My cat has chronic nasal issues. And she doesn't tolerate taking medication. I started using this about a month ago. I put it in her wet food and she eats it fine.