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PetDosageChart

Antibiotic / Antiprotozoal · For Dogs

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

Standard Metronidazole dose for dogs is 10 mg per kg (4.54 mg per lb), given every 8-12 hours. Use the calculator below for your dog's exact weight, or jump to the weight-by-weight chart.

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

Calculator estimate from Plumb’s Veterinary Drug Handbook. Not yet vet-reviewed — see our methodology .

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. Sourced from Plumb's Veterinary Drug Handbook and the Merck Veterinary Manual.

Dosage Calculator · 01

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By Weight

Flagyl dose by dog weight

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Dosage Chart · 02

Flagyl dosage for dogs by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe 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

Common Uses · 03

What is Flagyl (Metronidazole) used for in dogs?

diarrhea giardia inflammatory bowel disease anaerobic bacterial infections dental infections

Administration · 04

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 · 05

Side effects of Flagyl in dogs

Common side effects

nausea
decreased appetite
drooling (bitter taste)
diarrhea
lethargy

Serious side effects — call your vet

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

Emergency · 06

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

For Cats

Looking for Metronidazole dosage for cats?

View the Metronidazole dosage chart and calculator for cats.

Related · 08

Related medications for dogs

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 10 mg per kg (4.54 mg per lb) of body weight, given every 8-12 hours. The calculator multiplies that basis by your dog's weight and rounds to the closest available tablet size.
Last-reviewed status
Automated from Plumb’s, not yet vet-reviewed.

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

Frequently Asked · 07

Questions about this medication

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.

Safety · 10

More resources