A gray cat eating a pill.
A gray cat eating a pill. Photography by Elenica / Shutterstock.

Amoxicillin for Cats: Dosages, Side Effects and More

Stumped on the basics of amoxicillin for cats? Let’s look at why cats need it in the first place, the correct dosage, potential side effects and more.
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For many longtime cat guardians, amoxicillin for cats may not be a mystery. It is an antibiotic drug, in the penicillin family, used to prohibit the growth of bacteria. According to Tufts University and Medical News Today, it treats everything from bronchitis to Lyme disease to urinary tract infections in people. Amoxicillin for cats is used frequently on kitties with skin infections, urinary tract infections and ear infections.

When I asked my veterinarian, Shinnecock Animal Hospital’s Dr. Kelly Tierney (class of 2014), what she thought about the drug, she paused. “I learned the medications that became my ‘go-to’ drugs from my mentor. He always used an antibiotic in conjunction with clavulanic acid for ailments like urinary tract infections and gastrointestinal infections. So, I’d say newer vets are probably going with clavamox (an antibiotic with clavulanic acid) over amoxicillin, but it’s really your veterinarian’s call.” Depending on your vet’s preference, your cat may currently be on it. Here’s the scoop about amoxicillin for cats.

A gray cat ready to take a pill from a human.
A gray cat ready to take a pill from a human. Photography by radleyhebdon/istock.

When is amoxicillin for cats necessary?

At one point, amoxicillin was the updated version of penicillin (patented by Bristol-Myers, 1975). It was considered better because it would be active longer, as per PetMD. It’s used in the treatment of cats with infections caused by bacteria, such as wounds (like animal bites), bladder infections, tooth abscesses, eye or ear infections, skin infections and respiratory infections. It can be used on GI infections, but it’s not effective against parasites (like tapeworms). Antibiotics are also usually recommended after surgical procedures, but Cummings Veterinary Medical Center at Tufts University indicates it’s prescribed on a per-case basis.

If your cat’s been in a fight, got a scrape, has itchy ears or runny eyes or he’s scratching like crazy, a trip to the vet will determine the best treatment. Some conditions, like urinary tract infections, are elusive. If your cat starts behaving oddly, especially by urinating outside his litter box, take him to the vet with a urine sample. Chances are he’ll be taking amoxicillin.

Dosing amoxicillin for cats

  1. Follow the timetable. One of the most important things about amoxicillin for cats is to make sure you give the medication at the designated time and for the entire duration it’s prescribed — even if your cat’s symptoms are gone. If you stop the medication before the prescribed end-date, you are making your cat susceptible to an even worse ailment that might be impossible to treat. The World Health Organization states that antibiotic resistance is one of the biggest threats to global health!
  1. Never self-prescribe. Let’s say your cat seems to have an infection similar to the one he had last year and you have some amoxicillin from one of your illnesses in the house. Amoxicillin for cats is not the same as amoxicillin for people. Vetinfo reports it could be toxic to your cat. Confirm every ailment’s origins before treating it. It could be a viral infection, in which case, amoxicillin is useless.
  1. Get a second opinion. If you feel that your cat is taking a lot of antibiotics, and not really improving, go to another veterinarian. Along with a possible misdiagnosis, amoxicillin for cats and other antibiotics come with side effects. So being on them for a prolonged period of time without any improvement could be a red flag that something is wrong.

Potential side effects of amoxicillin for cats

Antibiotics, including amoxicillin, can cause a range of side effects for cats. Since every cat is an individual, each cat will respond differently to amoxicillin. PetCareRX mentions the following as the most prevalent side effects to antibiotics: rashes, fever, kidney or liver damage, diarrhea and vomiting.

Also, antibiotics can be particularly difficult on the digestive system, so confirm if your cat should take amoxicillin with or without food.

In addition, Vetinfo indicates that your cat could have dangerous complications if amoxicillin is taken while other antibiotics are in his system. And some cats are allergic to it. Monitor your cat closely while taking any medications, and alert your vet to anything out of the ordinary — health or behavior wise.

What about treating your cat with alternative medicine?

Take your cat to the veterinarian immediately any time he appears ill or injured. However, there are holistic approaches that can be effective in keeping your cat healthy in the first place, according to Dr. Shawn Messonnier, author of the Natural Health Bible for Dogs & Cats and Nutritional Supplements for the Veterinary Practice.

While we do not advocate using natural alternatives over traditional medications, learning more about supporting your cat’s immune system can help devise a lifelong healthy strategy. Amoxicillin for cats has many benefits, some side effects and should always be taken as directed by a professional vet. Communicating closely with your veterinarian is the best way to ensure your cat’s amoxicillin treatment is doing the trick to ensure his path to health and well-being.

Thumbnail: Photography by Elenica / Shutterstock.

This piece was originally published in 2017.

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42 thoughts on “Amoxicillin for Cats: Dosages, Side Effects and More”

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  2. My 12 year old male has it hy skin, constantly scratching. The problem, can’t find UN-Flavored benydryll anywhere. Everything thing is either bubble gum, grape, cherry, etc. He’s not having it. Any suggestions, anyone? Please, we’re desperate! Thanks ya’ll! Mary & my Buddy boy!

    1. Apparently Benadryl can have some bad side-effects in cats.
      It appears that a safer antihistamine for cats is “ZYRTEC” (The one WITHOUT Decongestant added).
      Get 10mg Tablets. (The liquids in capsules have more unnecessary ingredients).
      Typical Cat dosage is 5mg (1/2 Tab) EVERY OTHER DAY.
      You should check appropriateness and dosage with your vet.
      I use a Pill Crusher to crush 1/2 Tablet – and add it to a SMALL amount of Gerber Baby Food Chicken & Gravy. Cats like this a lot. (Use SMALL amount so you know the cat has eaten ALL of the Zyrtec).
      You can find this in general stores (CVS, Walgreens, Etc)
      AND – I would try to find the cause of the itching – and GET THAT TREATED PROPERLY. Have you had him checked by your vet?? It could be something SERIOUS. He could be dehydrated (Kidney Failure?) , have mites, allergies, Etc.

  3. I know taking a pet to the vets’ office is expensive ($500+ in 2 months), but they have been highly trained (just like your doctor) and know best. So do the right thing. Take your pet to the vet.

  4. My cat had a bad reaction from clavamox and did not with amoxicillian. Each animal is different. Just watch carefully when administering any medication and always know the side affects before hand.

  5. Melissa Benavides

    Thanks for all the advice! My husband and I try to help all of the feral s around here. We were going broke trying to get them all seen. Thank you all for the info.

  6. Iryna Potapenko

    My cat according to last test of urinalysis showed elevated protein, large hematuria and leukocytes trace. I have some augmentin left since last year I started give it to her 2 x 0.6 per day for the past 3 days and dont see much improvements. I also have amox 500 mg. What doses i should give to her?
    She is 6-7lb. Thank you.

    1. Randy Emile Henaire

      If your. Amos is the kind for humans you might want to investigate first…..they say it can be toxic for your car and that. The amps for cats and dogs is different…..im in the same boat as you

  7. Pingback: The Best Antibiotics for Cats | Share Your Pet – Pet Sharing – Local Dog Walking, Pet Sitting & Holiday Care

  8. Pingback: The Best Antibiotics for Cats – Share Your Pet – Pet Sharing – Local Dog Walking, Pet Sitting & Holiday Care

  9. lol “human” amoxicillin cause it’s extracted from the bigger trees! But seriously Amoxicillin is Amoxicillin. Humans use it,cats,dogs,birds and even fish. If you need some for you….r pet buys some “fish Mox”. 100 caps at 250mg each will have Gpa,Rover,Princess,Purdy birdy and Sir swimsalot feeling much better. (eBay,Amazon etc etc)Also comes in penicillin and 1 other common AB that escapes me.. Now it does say not for humans. Not sure the current prescription cost for 100 caps but I’m sure it’s WAY MORE than 15.00 US so if you’d rather not have a pic of a cute fish on your label by all means take the day off work,see the doc/vet,fill the script (and get no pic at all lol ). When you get thru the day go home and check your pills against the fish ones on google images…..identical. same pill, diff label, The preppers stock up on these for the “big day”. Just sharin. info here not advice….For the doubters….u get a script, your dog gets one, your cat gets one, but really,your gonna make me get one for my goldfish!! lol hence the soon to close loophole. Now the bad news…. not all issues will get better from Amox. It treats a lot of infections but not all. If everyone eats them like candy then the viruses will adapt and make it useless (that and $$ is why you need a script) so don’t start giving rover one a day to keep him healthy. Doses vary by weight (kitten 5mg a day you do the math)Double the first dose then 7-10 days then stop. Use sparingly,only when your sure it’s the correct med for the job. (do your research).
    For example:My cellulitis is acting up so I dropped 2. No more huge tender sores to live thru,stops them early and only need one a day after that for a couple days, but now I feel like going for a swim! lol (that’s a fish joke if you didn’t get it. :) ) Kind of breakin the rule but keep it on the DL

  10. If the generic answer is “take the cat to a vet or do nothing,” then say so. This is frustrating when trying to help feral animals an uncatchable strays.

  11. A friend of mine gave a 500mg dosage Amoxicillin tablet to a 1 year old stray cat!! Is the cat in danger now? what can she do?

    1. Why would she do that?? A 500 mg dose would treat approx. TWENTY 10 lb cats. She gave him 20 times the dosage. That poor cat.

      1. So WHY did you say dose in the title?! You totally misrepresented yourself, but congrats on the hits and making money from your advertisers! SMH…

  12. Pingback: The Best Antibiotics for Cats – petsbookco

  13. Follow up — although that “5 mg per pound of body weight per day” is at the absolute low end for recommended dosage — most vets would likely recommend at least twice a day for that dosage, unless there was some other co-morbidity involved.

  14. The link to VetInfo regarding amoxicillin states that it’s OK to give to cats.

    From the article:
    ” The human antibiotics that are suitable for use in felines include:

    “Amoxicillin, used to fight bacterial infections; the dosage should be 5 mg per pound of body weight per day
    “Ampicillin, employed for bacterial infections; the cat requires 10 mg per pound every 6 hours
    “Tetracycline, effective against bacterial infections; the dose is 10 mg per pound every 8 hours”

    1. Yes, VetInfo states that human amoxicillin is safe for cats, and getting him to a vet would require getting him into a carrier — which is not possible. It took 2 months of diligence just to get him positioned under a gigantic drop cage in order to get him neutered/vaccinated.

      He got in a fight and developed a huge abcess. Even the feral organization that helped us get him that drop cage advised giving him amoxicillin, 50 mg, twice a day. It seems to be working.

      1. Oh, I guess I should mention that my cat was feral, and lived in our backyard for 5 years. Since getting him fixed, we’ve been able to coax him inside, but won’t go near a cage/carrier.

  15. Hi,my cat has what’s known as rodent ulcers on his lips. I rang the vet for info on what to do without bringing him in (example home remedies like bathing in salt water and metacam) she did say he may need an anti biotic if this doesn’t work. Hence no luck with home remedies I have some amoxcillon here wich is prescribed for cats it says to give point 5 grams wich I have done in syringe form just wondering what is the full cycle for this antibiotic. ?

    1. Michaela Conlon

      Hi Michelle!

      Please contact your vet ASAP with this question about specific antibiotics. Hope your cat feels better!

  16. My cat has been overridden with fleas, i cleaned him up a lot but still a few stragglers. 3 days ago i put that dosage of pet armour on him along with getting rid of the fleas, still monitoring. My vet is unable to see him until late tomorrow i asked if an antibiotic would work & they said “possible” so i p.u. Augmentin & just gave him 1cc/1.0Ml (actually just a lil less) i need your opinion also, please

    1. Hi Andrea,
      We suggest working with your vet to get the flea issues under control. These articles might provide some insight as well:
      https://www.catster.com/cat-health-care/flea-treatment-for-cats
      https://www.catster.com/lifestyle/9-methods-natural-flea-control-cats
      https://www.catster.com/cat-health-care/the-regional-guide-to-fleas-and-ticks-on-cats
      https://www.catster.com/cat-health-care/how-to-fight-fleas-and-ticks-on-cats

  17. I agree. Even the first heading states “Let’s look at why cats need it in the first place, the correct dosage, potential side effects and more.” yet there isn’t a single line anywhere regarding what the correct dosage is (5-10mg/lb every 12 or 24 hours for 7-10 days according to the insert in my package of amoxicillin if anyone needs it).

    1. I need it bad. My friends cat (Sqirty McGee) was bitten by either another cat or spider and hes lying around in the dumps. My friend popped the top of his ear to drain it, i believe he needs amoxacillen, we have it for humans 800 mgs and its new, how many mgs. Should we give him? Theres no $$ for a vet. Any answers would be helpfful…
      Debbie

    2. I do have amoxicillin 250mg. Do I need to get a scale to weigh 5-10 mg? How best to give it to a cat? Oral syringe? TIA

  18. You nevery gave how many cc per weight of cat. Seems your trying to impress people with Mish mosh. When it says dosage in your heading then give it.

    1. Totally Agreed, I help stray cats all the time and if I took each one of them to the vet I would go broke. I live in a farming community and everyone treats their own animals if they know whats wrong with them, if they don’t they put out the money and call a vet. Veterinary care is a minimum of $300 to check for a upper respiratory infection, with xrays and blood work and all they do.. Of course if your cat is not eating or lethargic you should rush to a Vet right away but if its a runny nose and a cough I think its ok to try to treat yourself. We have the internet now and so information is a keystroke away, not like the old days where you had no choice but to go to a professional for everything. Love to all…Kitten

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