Nitroimidazole Antibiotic / Antiprotozoal · For Cats

Metronidazole dosage reference for cats (Flagyl)

This page's standard weight-based reference is 15 mg per kg (6.80 mg per lb), with Every 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 per dose
Class: Nitroimidazole Antibiotic / Antiprotozoal

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.

Metronidazole (often known by brand names such as Flagyl) is a nitroimidazole antibiotic / antiprotozoal commonly used in veterinary medicine for Inflammatory bowel disease (IBD), Giardia infection, Diarrhea of unknown cause, Anaerobic bacterial infections, and Periodontal disease. Understanding the correct dosage, administration, and potential side effects of Metronidazole is critical for your cat’s safety and well-being.

A typical Metronidazole dose for cats is around 15 mg/kg Every 12 hours, within a usual range of 10-25 mg/kg. Available forms include Tablet, Compounded liquid, and Injectable.

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.

Metronidazole Dosage Calculator for Cats

Enter your cat’s weight below to estimate the Metronidazole dose from the 15 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 Metronidazole amounts for common cat weights, for quick reference:

Dosage Chart · 02

Flagyl 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)	14.0 mg	21.0 mg	35.0 mg	Every 12 hours
4 lbs (1.8 kg)	18.0 mg	27.0 mg	45.0 mg	Every 12 hours
5 lbs (2.3 kg)	23.0 mg	34.5 mg	57.5 mg	Every 12 hours
6 lbs (2.7 kg)	27.0 mg	40.5 mg	67.5 mg	Every 12 hours
7 lbs (3.2 kg)	32.0 mg	48.0 mg	80.0 mg	Every 12 hours
8 lbs (3.6 kg)	36.0 mg	54.0 mg	90.0 mg	Every 12 hours
9 lbs (4.1 kg)	41.0 mg	61.5 mg	102.5 mg	Every 12 hours
10 lbs (4.5 kg)	45.0 mg	67.5 mg	112.5 mg	Every 12 hours
12 lbs (5.4 kg)	54.0 mg	81.0 mg	135.0 mg	Every 12 hours
14 lbs (6.3 kg)	63.0 mg	94.5 mg	157.5 mg	Every 12 hours
16 lbs (7.3 kg)	73.0 mg	109.5 mg	182.5 mg	Every 12 hours
18 lbs (8.2 kg)	82.0 mg	123.0 mg	205.0 mg (250mg tablet)	Every 12 hours
20 lbs (9.1 kg)	91.0 mg	136.5 mg	227.5 mg (250mg tablet)	Every 12 hours
25 lbs (11.3 kg)	113.0 mg	169.5 mg	282.5 mg (250mg tablet)	Every 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

Flagyl 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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How to Give Metronidazole to Your Cat

Metronidazole is extremely bitter, making it one of the hardest medications to give cats. NEVER crush the tablets. Give the tablet whole, coated in a small amount of butter or hidden inside a pill pocket. Use a pill gun/pill popper to place the tablet at the back of the tongue, then hold the mouth closed and gently stroke the throat. Follow immediately with a small syringe of water or tuna juice to help the tablet go down. If pilling is impossible, ask your vet for a compounded fish- or chicken-flavored liquid. Give with food to reduce GI upset.

It is generally recommended to give Metronidazole with food to help reduce stomach upset. It may interact with Phenobarbital (reduced metronidazole effectiveness), Warfarin (enhanced anticoagulant effect), Cimetidine (increased metronidazole levels), and Cyclosporine (increased toxicity risk).

Side Effects and Safety

Common side effects include Nausea and loss of appetite, Drooling (extremely bitter taste), Vomiting, and Diarrhea (paradoxical). More serious side effects can occur, such as Neurotoxicity (ataxia, seizures, head tilt) at high doses or prolonged use, Liver toxicity, Severe allergic reaction, and Blood disorders (neutropenia).

Cautions · 12

When Flagyl should be used with caution or avoided

Some cats should not take Flagyl, 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 Flagyl.

Known hypersensitivity to metronidazole or nitroimidazoles
Severe liver disease
Pregnant or nursing queens
Young kittens under 8 weeks

Interactions · 13

Flagyl drug interactions

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

Phenobarbital (reduced metronidazole effectiveness)

Warfarin (enhanced anticoagulant effect)

Cimetidine (increased metronidazole levels)

Cyclosporine (increased toxicity risk)

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 Flagyl, 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:

Wobbling, stumbling, or loss of coordination (possible neurotoxicity)
Seizures or abnormal eye movements
Persistent vomiting or refusal to eat for more than 24 hours
Yellowing of gums or eyes (possible liver issues)
Signs of an allergic reaction: facial swelling, hives, or difficulty breathing

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

Why is metronidazole so hard to give to cats?

Metronidazole is extremely bitter-tasting, and cats are notoriously sensitive to bitter flavors. Even a small amount of crushed tablet can cause excessive drooling and foaming at the mouth. This is why many veterinarians recommend compounded flavored liquid formulations or coating the tablet so the cat cannot taste it. Never crush metronidazole tablets to mix with food unless specifically directed.

How long can my cat take metronidazole?

Short courses of 5-14 days are typical for infections and diarrhea. For IBD, some cats require longer courses, but extended use beyond 2-3 weeks increases the risk of neurotoxicity. Your vet will determine the appropriate duration. Signs of neurotoxicity include wobbling, head tilt, and disorientation—stop the medication and contact your vet immediately if you see these.

Can metronidazole cause neurological problems in cats?

Yes. Metronidazole neurotoxicity is a well-documented risk, especially at higher doses (above 25 mg/kg/day) or with prolonged use. Signs include loss of balance, abnormal eye movements, head tilt, and in severe cases, seizures. The good news is that neurotoxicity is usually reversible once the drug is discontinued, though recovery may take days to weeks.

Does metronidazole treat giardia in cats?

Metronidazole is commonly used to treat giardia in cats, though fenbendazole (Panacur) is often preferred as a first-line treatment. Metronidazole is typically given at 15-25 mg/kg every 12 hours for 5-7 days for giardia. Some vets use both drugs together for stubborn cases. Environmental decontamination is also important to prevent reinfection.

What if my cat drools after taking metronidazole?

Drooling is a very common reaction due to the extremely bitter taste and does not indicate an allergic reaction. If your cat bites into the tablet, expect significant drooling and foaming. To minimize this, give the tablet whole (do not crush), coat it in butter or a pill pocket, or switch to a compounded flavored formulation. The drooling should stop within 15-30 minutes.

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 Flagyl. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses: Inflammatory bowel disease (IBD), Giardia infection, Diarrhea of unknown cause, Anaerobic bacterial infections, Periodontal disease
Recorded forms: Tablet, Compounded liquid, Injectable
Reference timing: Every 12 hours; onset 1-2 hours; duration 8-12 hours per dose

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 hypersensitivity to metronidazole or nitroimidazoles; Severe liver disease; Pregnant or nursing queens; Young kittens under 8 weeks.

Recorded interactions

Phenobarbital (reduced metronidazole effectiveness); Warfarin (enhanced anticoagulant effect); Cimetidine (increased metronidazole levels); Cyclosporine (increased toxicity risk).

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 Metronidazole — 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 15 mg per kg (6.80 mg per lb) of body weight, given Every 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