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PetDosageChart

Flagyl (Metronidazole) Dosage for Cats

Nitroimidazole Antibiotic / Antiprotozoal ⏱ Onset: 1-2 hours ⏳ Duration: 8-12 hours per dose

This dosage information is for educational purposes only. Always consult your veterinarian before giving any medication to your pet. Dosages may vary based on your pet's health conditions, other medications, and individual factors.

Content reviewed by licensed veterinarians. This information is sourced from veterinary drug references including Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

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Flagyl Dosage Chart for Cats by Weight

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Weight Low Dose Standard Dose Max Dose 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

What is Flagyl (Metronidazole) used for in cats?

Inflammatory bowel disease (IBD) Giardia infection Diarrhea of unknown cause Anaerobic bacterial infections Periodontal disease

How to give Flagyl 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.

Available Forms

Tablet, Compounded liquid, Injectable

Give with Food?

Yes — give with food

Side effects of Flagyl in cats

Common side effects

Nausea and loss of appetite
Drooling (extremely bitter taste)
Vomiting
Diarrhea (paradoxical)

Serious side effects

  • Neurotoxicity (ataxia, seizures, head tilt) at high doses or prolonged use
  • Liver toxicity
  • Severe allergic reaction
  • Blood disorders (neutropenia)

When to call the vet

Call your vet immediately if your cat shows any of these signs:

  • 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

Related Medications for Cats

Antibiotic (Penicillin)

Amoxil

Amoxicillin

For bacterial infections

View dosage chart
Antibiotic (Tetracycline)

Vibramycin

Doxycycline

For upper respiratory infections

View dosage chart
First-Generation Cephalosporin Antibiotic

Keflex

Cephalexin

For Skin and soft tissue infections

View dosage chart
Fluoroquinolone antibiotic

Baytril

Enrofloxacin

For bacterial infections

View dosage chart

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.

Frequently Asked Questions

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.

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