Antibiotic / Antiprotozoal · For Dogs

Metronidazole dosage reference for dogs (Flagyl)

This page's standard weight-based reference is 10 mg per kg (4.54 mg per lb), with every 8-12 hours recorded as the reference frequency. Use the calculator to see the arithmetic for your dog's weight, then confirm the indication, product, and actual dose with a veterinarian.

Onset: 1-2 hours
Duration: 8-12 hours
Class: 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 an antibiotic / antiprotozoal commonly used in veterinary medicine for diarrhea, giardia, inflammatory bowel disease, anaerobic bacterial infections, and dental infections. Understanding the correct dosage, administration, and potential side effects of Metronidazole is critical for your dog’s safety and well-being.

A typical Metronidazole dose for dogs is around 10 mg/kg every 8-12 hours, within a usual range of 5-25 mg/kg. Available forms include tablet, capsule, and liquid.

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 Dogs

Enter your dog’s weight below to estimate the Metronidazole dose from the 10 mg/kg guideline. Your veterinarian may adjust it for your dog’s age, condition, and other medications, so treat the result as an educational starting point, not a prescription.

Dosage Calculator · 01

Enter your dog's weight

Quick Dosage Chart

Typical Metronidazole amounts for common dog weights, for quick reference:

Dosage Chart · 02

Flagyl weight-based reference chart for dogs

Scroll sideways to see full table

Weight	Lower Reference	Standard Reference	Upper Reference	Frequency
5 lbs (2.3 kg)	11.5 mg	23.0 mg	57.5 mg	every 8-12 hours
10 lbs (4.5 kg)	22.5 mg	45.0 mg	112.5 mg	every 8-12 hours
15 lbs (6.8 kg)	34.0 mg	68.0 mg	170.0 mg	every 8-12 hours
20 lbs (9.1 kg)	45.5 mg	91.0 mg	227.5 mg (250mg tablet)	every 8-12 hours
25 lbs (11.3 kg)	56.5 mg	113.0 mg	282.5 mg (250mg tablet)	every 8-12 hours
30 lbs (13.6 kg)	68.0 mg	136.0 mg	340.0 mg	every 8-12 hours
40 lbs (18.1 kg)	90.5 mg	181.0 mg	452.5 mg (2 × 250mg)	every 8-12 hours
50 lbs (22.7 kg)	113.5 mg	227.0 mg (250mg tablet)	567.5 mg	every 8-12 hours
60 lbs (27.2 kg)	136.0 mg	272.0 mg (250mg tablet)	680.0 mg	every 8-12 hours
70 lbs (31.7 kg)	158.5 mg	317.0 mg	792.5 mg (3 × 250mg)	every 8-12 hours
80 lbs (36.3 kg)	181.5 mg	363.0 mg	907.5 mg	every 8-12 hours
90 lbs (40.8 kg)	204.0 mg (250mg tablet)	408.0 mg	1020.0 mg (4 × 250mg)	every 8-12 hours
100 lbs (45.4 kg)	227.0 mg (250mg tablet)	454.0 mg (2 × 250mg)	1135.0 mg	every 8-12 hours
120 lbs (54.4 kg)	272.0 mg (250mg tablet)	544.0 mg (2 × 250mg)	1360.0 mg	every 8-12 hours
150 lbs (68 kg)	340.0 mg	680.0 mg	1700.0 mg (7 × 250mg)	every 8-12 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 dog 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 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.

It is generally recommended to give Metronidazole with food to help reduce stomach upset. It may interact with phenobarbital, cimetidine, cyclosporine, anticoagulants, and phenytoin.

Side Effects and Safety

Common side effects include nausea, decreased appetite, drooling (bitter taste), diarrhea, and lethargy. More serious side effects can occur, such as neurotoxicity (at high doses or prolonged use), seizures, head tilt, liver toxicity, and blood in urine.

Cautions · 12

When Flagyl should be used with caution or avoided

Some dogs 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.

puppies under 12 weeks
pregnant or nursing dogs
liver disease
known hypersensitivity

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 dog's medications and supplements.

phenobarbital

cimetidine

cyclosporine

anticoagulants

phenytoin

Calculator Limits · 14

When not to use this calculator

This calculator gives a general educational estimate for a healthy adult dog 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 dogs
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 dog's current, accurate weight
For combination products that contain additional active ingredients

Overdose · 15

Suspected overdose: what to do

If you think your dog 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 dog experiences any of the following, contact your veterinarian or an emergency clinic immediately:

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

Frequently Asked Questions

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.

Use This Guide Safely · 08

What weight alone cannot tell you

The calculator performs one narrow job: it multiplies your dog'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: diarrhea, giardia, inflammatory bowel disease, anaerobic bacterial infections, dental infections
Recorded forms: tablet, capsule, liquid
Reference timing: every 8-12 hours; onset 1-2 hours; duration 8-12 hours

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

puppies under 12 weeks; pregnant or nursing dogs; liver disease; known hypersensitivity.

Recorded interactions

phenobarbital; cimetidine; cyclosporine; anticoagulants; phenytoin.

These lists reproduce the structured record used by this page and may not be exhaustive. Show your veterinarian the product label and your dog's complete medication list before acting on a number.

Related · 08

Related medications for dogs

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 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 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 dogs 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