Amoxicillin is safe for cats when prescribed by a veterinarian. It is an FDA-approved antibiotic used in feline medicine to treat bacterial skin infections, soft tissue infections like wounds and abscesses, and urinary tract infections. Both plain amoxicillin and its combination form with clavulanate potassium (sold as Clavamox) have been used in cats since the mid-1980s.
What Amoxicillin Treats in Cats
Veterinarians prescribe amoxicillin for cats most commonly for three categories of bacterial infection: skin and soft tissue problems (wounds, abscesses, and skin infections), urinary tract infections caused by E. coli, and upper respiratory infections. The drug works by disrupting the cell walls of bacteria, killing them rather than just slowing their growth.
Your vet may prescribe the combination version, amoxicillin-clavulanate, instead of plain amoxicillin. The added ingredient disables a defense mechanism that some bacteria use to resist the antibiotic. This makes the combination effective against a broader range of bacteria, including certain staph strains that plain amoxicillin can’t handle on its own.
Standard Dosing and Duration
The recommended dose for cats is 50 mg once daily. Treatment typically lasts 5 to 7 days, or until 48 hours after all symptoms have cleared, whichever is longer. Your vet may adjust the dose or frequency depending on the type and severity of infection.
Amoxicillin comes in tablet form and as a liquid suspension. The liquid version is often easier to give cats and is supplied as a powder that gets mixed with water at the pharmacy. Once mixed, it needs to be refrigerated and shaken well before each dose. Any leftover liquid should be thrown away after 14 days.
Common Side Effects
Most cats tolerate amoxicillin well. The side effects that do occur are usually mild and digestive: nausea, diarrhea, or reduced appetite. If your cat vomits after taking it on an empty stomach, giving it with food typically solves the problem. The drug absorbs fine either way, so there’s no downside to pairing it with a meal.
Rarely, more serious reactions have been reported, including fever, skin rashes, and bone marrow suppression. These are uncommon enough that amoxicillin is considered one of the safer antibiotics available for cats.
Signs of an Allergic Reaction
Like all penicillin-type antibiotics, amoxicillin can trigger an allergic reaction in sensitive cats. This is the most serious risk, and it typically shows up within hours of a dose. Watch for swelling around the face or muzzle, hives or raised bumps on the skin, rapid breathing, difficulty breathing, or an unusually fast heart rate. If you notice any of these signs, stop giving the medication and contact your vet immediately. Cats with a known allergy to any penicillin or cephalosporin antibiotic should never be given amoxicillin.
Why You Shouldn’t Use Human Amoxicillin
Human amoxicillin contains the same active ingredient as the veterinary version, which is why some cat owners wonder if they can skip the vet visit and use what’s in their medicine cabinet. This is a bad idea for several reasons. Human formulations often contain artificial sweeteners, flavorings, or inactive ingredients that can be harmful to cats. The dosing is also designed for a 150-pound adult, not a 10-pound cat, making accidental overdose easy. And without a proper diagnosis, you could be treating the wrong problem entirely, giving bacteria time to develop resistance while your cat’s actual condition worsens.
Amoxicillin only works against bacterial infections. It does nothing for viral infections, which are actually the more common cause of upper respiratory symptoms in cats. A vet visit ensures the right diagnosis comes before the prescription.
Cats That Shouldn’t Take Amoxicillin
Beyond cats with known penicillin allergies, there are a few other situations where caution is warranted. The safety of amoxicillin in pregnant or breeding cats has not been fully established, though it does cross the placenta and is generally considered low-risk during pregnancy. If your cat is on other medications, let your vet know, as drug interactions can affect how well amoxicillin works or increase the chance of side effects.
Cats with kidney disease may need dose adjustments since the drug is cleared through the kidneys. Your vet will factor in your cat’s overall health before prescribing.
Finishing the Full Course
One of the most common mistakes cat owners make is stopping amoxicillin early because their cat seems better. Symptoms often improve within two or three days, but the infection may not be fully cleared. Stopping too soon allows surviving bacteria to bounce back, potentially creating a harder-to-treat infection the second time around. Stick to the full course your vet prescribed, even if your cat is acting completely normal before the medication runs out.