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PetDosageChart

Flagyl (Metronidazole) Dosage for Dogs

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

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 Dogs by Weight

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Weight Low Dose Standard Dose Max Dose Frequency
5 lbs (2.3 kg) 11.5mg 23mg 57.5mg every 8-12 hours
10 lbs (4.5 kg) 22.5mg 45mg 112.5mg every 8-12 hours
15 lbs (6.8 kg) 34mg 68mg 170mg every 8-12 hours
20 lbs (9.1 kg) 45.5mg 91mg 227.5mg (250mg tablet) every 8-12 hours
25 lbs (11.3 kg) 56.5mg 113mg 282.5mg (250mg tablet) every 8-12 hours
30 lbs (13.6 kg) 68mg 136mg 340mg every 8-12 hours
40 lbs (18.1 kg) 90.5mg 181mg 452.5mg (2 × 250mg) every 8-12 hours
50 lbs (22.7 kg) 113.5mg 227mg (250mg tablet) 567.5mg every 8-12 hours
60 lbs (27.2 kg) 136mg 272mg (250mg tablet) 680mg every 8-12 hours
70 lbs (31.7 kg) 158.5mg 317mg 792.5mg (3 × 250mg) every 8-12 hours
80 lbs (36.3 kg) 181.5mg 363mg 907.5mg every 8-12 hours
90 lbs (40.8 kg) 204mg (250mg tablet) 408mg 1020mg (4 × 250mg) every 8-12 hours
100 lbs (45.4 kg) 227mg (250mg tablet) 454mg (2 × 250mg) 1135mg every 8-12 hours
120 lbs (54.4 kg) 272mg (250mg tablet) 544mg (2 × 250mg) 1360mg every 8-12 hours
150 lbs (68 kg) 340mg 680mg 1700mg (7 × 250mg) every 8-12 hours

What is Flagyl (Metronidazole) used for in dogs?

diarrhea giardia inflammatory bowel disease anaerobic bacterial infections dental infections

How to give Flagyl to your dog

Metronidazole has a very bitter taste that dogs dislike. Give with food to mask the taste and reduce stomach upset. Do not crush the tablets if possible, as this releases the bitter flavor. If your dog refuses to take it, ask your vet about compounding it into a flavored liquid.

Available Forms

tablet, capsule, liquid

Give with Food?

Yes — give with food

Side effects of Flagyl in dogs

Common side effects

nausea
decreased appetite
drooling (bitter taste)
diarrhea
lethargy

Serious side effects

  • neurotoxicity (at high doses or prolonged use)
  • seizures
  • head tilt
  • liver toxicity
  • blood in urine

When to call the vet

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

  • Staggering, head tilt, or abnormal eye movements (signs of neurotoxicity)
  • Seizures or tremors
  • Severe vomiting or refusal to eat for more than 24 hours
  • Blood in urine or dark urine
  • Symptoms worsen despite treatment

Related Medications for Dogs

Antibiotic (Penicillin)

Amoxil

Amoxicillin

For bacterial infections

View dosage chart
Antibiotic (Tetracycline)

Vibramycin

Doxycycline

For tick-borne diseases (Lyme, ehrlichiosis)

View dosage chart
Antibiotic (Cephalosporin)

Keflex

Cephalexin

For skin infections (pyoderma)

View dosage chart
Fluoroquinolone antibiotic

Baytril

Enrofloxacin

For Urinary tract 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

What does metronidazole treat in dogs?
Metronidazole is commonly used to treat diarrhea, giardia infections, inflammatory bowel disease (IBD), and anaerobic bacterial infections in dogs. It is particularly effective against protozoan parasites and bacteria that thrive in oxygen-poor environments.
How long does metronidazole take to work in dogs?
Metronidazole typically begins improving symptoms within 24-48 hours. For diarrhea, you may see firmer stools within 1-2 days. For giardia, a full 5-7 day course is usually needed. Complete the entire prescribed course even if symptoms improve.
Can metronidazole cause neurological problems in dogs?
Yes, at high doses or with prolonged use, metronidazole can cause neurotoxicity in dogs. Signs include head tilt, stumbling, rapid eye movements, and seizures. This is more common when doses exceed 60 mg/kg/day or treatment extends beyond 2 weeks. If you notice any neurological signs, stop the medication and contact your vet immediately.
Why does my dog drool after taking metronidazole?
Metronidazole is extremely bitter. If the tablet is crushed, chewed, or partially dissolved in the mouth, dogs will drool excessively due to the taste. Give the tablet whole, hidden in a treat or pill pocket, to minimize this reaction.

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