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PetDosageChart

Nitroimidazole Antibiotic / Antiprotozoal · For Cats

How much Metronidazole (Flagyl) can I give my cat?

Standard Metronidazole dose for cats is 15 mg per kg (6.80 mg per lb), given Every 12 hours. Use the calculator below for your cat's exact weight, or jump to the weight-by-weight chart.

Onset
1-2 hours
Duration
8-12 hours per dose
Class
Nitroimidazole Antibiotic / Antiprotozoal

Calculator estimate from Plumb’s Veterinary Drug Handbook. Independent DVM review is being added page by page — 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.

Dosage data is sourced from Plumb's Veterinary Drug Handbook and cross-referenced with Merck Veterinary Manual and DailyMed where applicable. Independent DVM review is being added page by page. See our methodology.

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 dosage for cats by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe Frequency
3 lbs (1.4 kg) 14mg 21mg 35mg Every 12 hours
4 lbs (1.8 kg) 18mg 27mg 45mg Every 12 hours
5 lbs (2.3 kg) 23mg 34.5mg 57.5mg Every 12 hours
6 lbs (2.7 kg) 27mg 40.5mg 67.5mg Every 12 hours
7 lbs (3.2 kg) 32mg 48mg 80mg Every 12 hours
8 lbs (3.6 kg) 36mg 54mg 90mg Every 12 hours
9 lbs (4.1 kg) 41mg 61.5mg 102.5mg Every 12 hours
10 lbs (4.5 kg) 45mg 67.5mg 112.5mg Every 12 hours
12 lbs (5.4 kg) 54mg 81mg 135mg Every 12 hours
14 lbs (6.3 kg) 63mg 94.5mg 157.5mg Every 12 hours
16 lbs (7.3 kg) 73mg 109.5mg 182.5mg Every 12 hours
18 lbs (8.2 kg) 82mg 123mg 205mg (250mg tablet) Every 12 hours
20 lbs (9.1 kg) 91mg 136.5mg 227.5mg (250mg tablet) Every 12 hours
25 lbs (11.3 kg) 113mg 169.5mg 282.5mg (250mg tablet) Every 12 hours

By Weight

Flagyl dose by cat weight

Pick your cat's weight to jump to a dedicated page with the dose, frequency, safety notes, and FAQ for that size.

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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:

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.

For Dogs

Looking for Metronidazole dosage for dogs?

View the Metronidazole dosage chart and calculator for dogs.

Related · 08

Related medications for cats

Sources · 09

Sources & references

The dosage information on this page is compiled from the following veterinary and pharmaceutical references:

  • Plumb's Veterinary Drug Handbook — the standard veterinary pharmacology reference used by veterinarians worldwide.
  • Merck Veterinary Manual — a trusted, peer-reviewed resource for veterinary professionals and pet owners.
  • DailyMed (FDA Drug Labels) — official FDA-approved drug labeling and prescribing information for Metronidazole.

Read more about our methodology and how we calculate dosages.

Transparency · 11

How this page was made

Sourced from Plumb's Veterinary Drug Handbook, the reference used in US vet schools. Every dose, frequency, and tablet count on this page is generated from that data, then checked against the published references below.

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 rounds to the closest available tablet size.
Last-reviewed status
Independent DVM review is being added page by page.

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

Safety · 10

More resources