Antibiotic (Penicillin) · For Cats

Amoxicillin dosage reference for cats (Amoxil)

This page's standard weight-based reference is 10 mg per kg (4.54 mg per lb), with every 8-12 hours recorded as the reference frequency. Use the calculator to see the arithmetic for your cat's weight, then confirm the indication, product, and actual dose with a veterinarian.

Onset: 1-2 hours
Duration: 8-12 hours
Class: Antibiotic (Penicillin)

Weight-based calculator estimate from the references listed on this page. This page has not been independently DVM-reviewed — see our methodology .

This information is for educational purposes only. Always consult your veterinarian before giving medication to your pet. Do not use this calculator for emergencies, overdoses, pregnancy, very young animals, very old animals, pets with liver/kidney disease, or pets taking multiple medications.

Each medication page lists the references recorded for its data. The calculator math and editorial presentation are maintained by PetDosageChart; a page is independently DVM-reviewed only when a named reviewer byline appears. See our methodology and limitations.

Amoxicillin (often known by brand names such as Amoxil and Clavamox (with clavulanate)) is an antibiotic (penicillin) commonly used in veterinary medicine for bacterial infections, skin infections, urinary tract infections, upper respiratory infections, and dental infections. Understanding the correct dosage, administration, and potential side effects of Amoxicillin is critical for your cat’s safety and well-being.

A typical Amoxicillin dose for cats is around 10 mg/kg every 8-12 hours, within a usual range of 5-25 mg/kg. Available forms include tablet and liquid suspension.

Calculator Warning: Use this only as an educational estimate. Your veterinarian may prescribe a different dose based on your pet’s condition, age, weight, other medications, and medical history.

Amoxicillin Dosage Calculator for Cats

Enter your cat’s weight below to estimate the Amoxicillin dose from the 10 mg/kg guideline. Your veterinarian may adjust it for your cat’s age, condition, and other medications, so treat the result as an educational starting point, not a prescription.

Dosage Calculator · 01

Enter your cat's weight

Quick Dosage Chart

Typical Amoxicillin amounts for common cat weights, for quick reference:

Dosage Chart · 02

Amoxil weight-based reference chart for cats

Scroll sideways to see full table

Weight	Lower Reference	Standard Reference	Upper Reference	Frequency
3 lbs (1.4 kg)	7.0 mg	14.0 mg	35.0 mg	every 8-12 hours
4 lbs (1.8 kg)	9.0 mg	18.0 mg	45.0 mg (50mg tablet)	every 8-12 hours
5 lbs (2.3 kg)	11.5 mg	23.0 mg	57.5 mg (50mg tablet)	every 8-12 hours
6 lbs (2.7 kg)	13.5 mg	27.0 mg	67.5 mg	every 8-12 hours
7 lbs (3.2 kg)	16.0 mg	32.0 mg	80.0 mg	every 8-12 hours
8 lbs (3.6 kg)	18.0 mg	36.0 mg	90.0 mg (2 × 50mg)	every 8-12 hours
9 lbs (4.1 kg)	20.5 mg	41.0 mg (50mg tablet)	102.5 mg (2 × 50mg)	every 8-12 hours
10 lbs (4.5 kg)	22.5 mg	45.0 mg (50mg tablet)	112.5 mg	every 8-12 hours
12 lbs (5.4 kg)	27.0 mg	54.0 mg (50mg tablet)	135.0 mg	every 8-12 hours
14 lbs (6.3 kg)	31.5 mg	63.0 mg	157.5 mg (3 × 50mg)	every 8-12 hours
16 lbs (7.3 kg)	36.5 mg	73.0 mg	182.5 mg	every 8-12 hours
18 lbs (8.2 kg)	41.0 mg (50mg tablet)	82.0 mg	205.0 mg (4 × 50mg)	every 8-12 hours
20 lbs (9.1 kg)	45.5 mg (50mg tablet)	91.0 mg (2 × 50mg)	227.5 mg	every 8-12 hours
25 lbs (11.3 kg)	56.5 mg (50mg tablet)	113.0 mg	282.5 mg	every 8-12 hours

Parenthetical tablet amounts are arithmetic comparisons only. They do not account for scoring, release type, concentration, product labeling, or whether this medication is appropriate for an individual animal.

By Weight

Amoxil reference by cat weight

Choose a common weight to open its optional reference page. Use the main medication calculator for a different exact weight.

Common-weight pages are convenience views of the same educational reference, not separate medical recommendations.

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Weight Does Not Choose the Antibiotic or the Course

The calculator applies the 10 mg/kg standard value stored in this page’s record. It cannot determine whether an illness is bacterial, whether amoxicillin is likely to work, or how long treatment should continue. Infection location, prior antibiotics, test results, kidney function, and the cat’s ability to take the product can all change the prescription.

Plain amoxicillin and amoxicillin/clavulanate products such as Clavamox are not interchangeable names for the same formulation. Liquid concentrations also vary after reconstitution. Use the exact label and syringe supplied for the prescribed product rather than converting from a different bottle or using leftovers.

Ask what improvement should occur and by when. Worsening symptoms, facial swelling, breathing difficulty, repeated vomiting, or severe diarrhea need prompt veterinary advice rather than an unapproved dose change.

How to Give Amoxicillin to Your Cat

If a liquid is prescribed, use only the concentration, measuring device, storage instructions, and course length printed on that dispensed label. Amoxicillin/clavulanate products are different formulations from plain amoxicillin. Do not use leftovers or stop, extend, or change a prescribed course without contacting the clinic.

It is generally recommended to give Amoxicillin with food to help reduce stomach upset. It may interact with methotrexate, bacteriostatic antibiotics, and anticoagulants.

Side Effects and Safety

Common side effects include diarrhea, vomiting, decreased appetite, and drooling. More serious side effects can occur, such as allergic reaction (facial swelling, hives), severe diarrhea, and difficulty breathing.

Cautions · 12

When Amoxil should be used with caution or avoided

Some cats should not take Amoxil, or need a different dose and closer monitoring. Tell your veterinarian about your pet's full health history and every other medication or supplement they take before giving Amoxil.

known penicillin allergy
known hypersensitivity

Interactions · 13

Amoxil drug interactions

Amoxil can interact with other drugs. This list is not complete — always give your veterinarian a full list of your cat's medications and supplements.

methotrexate

bacteriostatic antibiotics

anticoagulants

Calculator Limits · 14

When not to use this calculator

This calculator gives a general educational estimate for a healthy adult cat at a known weight. Do not rely on it in these situations — talk to your veterinarian instead:

In an emergency, or after accidental ingestion or a suspected overdose
For pregnant or nursing pets
For very young or very old cats
For pets with liver disease, kidney disease, or another chronic illness
For pets taking several medications at once
When you are not sure of your cat's current, accurate weight
For combination products that contain additional active ingredients

Overdose · 15

Suspected overdose: what to do

If you think your cat had too much Amoxil, or swallowed any medication by accident, act right away. Do not wait for symptoms to appear.

Call your veterinarian or the nearest emergency animal hospital.
ASPCA Animal Poison Control Center: (888) 426-4435
Pet Poison Helpline: (855) 764-7661

A consultation fee may apply to the poison hotlines. Have the medication packaging ready, and note how much your pet may have taken and when. Do not try to make your pet vomit unless a veterinarian tells you to.

When to Call the Vet

If your cat experiences any of the following, contact your veterinarian or an emergency clinic immediately:

Signs of allergic reaction (facial swelling, difficulty breathing)
Severe or bloody diarrhea
Refusal to eat for more than 24 hours
No improvement after 48-72 hours
Vomiting after every dose

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

Can I give my cat amoxicillin?

Amoxicillin is commonly prescribed for cats by veterinarians for various bacterial infections. However, you should never give your cat amoxicillin without a prescription — the vet needs to diagnose the infection, determine if an antibiotic is appropriate, and calculate the correct dose for your cat.

How much amoxicillin do I give my cat?

The typical dose for cats is 5-10 mg per kilogram of body weight, given every 12 hours. For an average 10 lb (4.5 kg) cat, this is approximately 45-90 mg per dose. The liquid suspension is easiest to dose accurately for cats.

What are the side effects of amoxicillin in cats?

The most common side effects in cats are digestive — diarrhea, vomiting, and decreased appetite. These are usually mild. Serious allergic reactions are rare but require immediate veterinary attention. Probiotics may help reduce GI side effects.

How long does a cat take amoxicillin?

A typical course is 7-14 days, depending on the infection type and severity. Upper respiratory infections may need 10-14 days. Always complete the full prescribed course to prevent antibiotic resistance, even if your cat appears better.

Use This Guide Safely · 08

What weight alone cannot tell you

The calculator performs one narrow job: it multiplies your cat's weight by the lower, standard, and upper mg/kg values recorded for Amoxil. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses: bacterial infections, skin infections, urinary tract infections, upper respiratory infections, dental infections
Recorded forms: tablet, liquid suspension
Reference timing: every 8-12 hours; onset 1-2 hours; duration 8-12 hours

Individual checks a calculator cannot perform

Confirm the diagnosis and the reason this medication is being considered.
Match the exact product, concentration, route, and whether a tablet may be split.
Account for age, pregnancy, organ function, genetics, allergies, and prior reactions.
Review every prescription, over-the-counter product, and supplement your pet takes.

Recorded cautions

known penicillin allergy; known hypersensitivity.

Recorded interactions

methotrexate; bacteriostatic antibiotics; anticoagulants.

These lists reproduce the structured record used by this page and may not be exhaustive. Show your veterinarian the product label and your cat's complete medication list before acting on a number.

Related · 08

Related medications for cats

Sources · 09

Sources & references

The structured medication record behind this page names the references below. The links open the publisher or official resource; they do not turn this page into a prescription for an individual animal.

Plumb's Veterinary Drug Handbook — listed in this medication's source record.
Merck Veterinary Manual — listed in this medication's source record.
DailyMed label search for Amoxicillin — check current product and formulation labels; some veterinary uses may be off-label.

Source names are shown at the record level; passage-level page and label citations are still being added. Read our methodology and limitations.

Transparency · 11

How this page was made

This page's structured medication record includes Plumb's Veterinary Drug Handbook among its source names. PetDosageChart applies the record's mg/kg values to the entered weight and presents the arithmetic result. A source record is not the same as an individualized prescription or an independent clinical review.

Sources cited: Plumb's Veterinary Drug Handbook
Merck Veterinary Manual
Calculator formula: Doses scale linearly from a standard basis of 10 mg per kg (4.54 mg per lb) of body weight, given every 8-12 hours. The calculator multiplies that basis by your cat's weight and shows an arithmetic comparison with recorded tablet sizes. That comparison does not determine whether a tablet is scored, splittable, or appropriate for your pet.
Editorial owner: Prepared and maintained by the PetDosageChart editorial team, a software-led publisher and not a veterinary practice.
DVM review status: Not independently DVM-reviewed. A named reviewer and review date appear here only after a confirmed review.

More on our methodology and editorial process — how we source, calculate, and review cats dosage data.

Safety · 10

More resources

Pet Medication Safety Hub — What's safe, what's dangerous, and emergency signs
How we calculate dosages — Our sources, math, and review process
Printable emergency checklist — One-page reference for your fridge or first aid kit