Antiparasitic · For Dogs

Ivermectin dosage reference for dogs (Ivomec)

This page's standard weight-based reference is 0.006 mg per kg (0.00 mg per lb), with once monthly (heartworm prevention) or as directed 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: 4-12 hours
Duration: 30 days (heartworm prevention)
Class: Antiparasitic

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.

Ivermectin (often known by brand names such as Ivomec and Heartgard) is an antiparasitic commonly used in veterinary medicine for heartworm prevention, mange (demodectic/sarcoptic), ear mites, and intestinal parasites. Understanding the correct dosage, administration, and potential side effects of Ivermectin is critical for your dog’s safety and well-being.

A typical Ivermectin dose for dogs is around 0.006 mg/kg once monthly (heartworm prevention) or as directed, within a usual range of 0.006-0.012 mg/kg. Available forms include tablet, chewable, injectable, and topical.

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.

Ivermectin Dosage Calculator for Dogs

Enter your dog’s weight below to estimate the Ivermectin dose from the 0.006 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 Ivermectin amounts for common dog weights, for quick reference:

Dosage Chart · 02

Ivomec 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)	0.014 mg	0.014 mg	0.028 mg	once monthly (heartworm prevention) or as directed
10 lbs (4.5 kg)	0.027 mg	0.027 mg	0.054 mg	once monthly (heartworm prevention) or as directed
15 lbs (6.8 kg)	0.041 mg	0.041 mg	0.082 mg	once monthly (heartworm prevention) or as directed
20 lbs (9.1 kg)	0.055 mg	0.055 mg	0.11 mg	once monthly (heartworm prevention) or as directed
25 lbs (11.3 kg)	0.068 mg	0.068 mg	0.14 mg	once monthly (heartworm prevention) or as directed
30 lbs (13.6 kg)	0.082 mg	0.082 mg	0.16 mg	once monthly (heartworm prevention) or as directed
40 lbs (18.1 kg)	0.11 mg	0.11 mg	0.22 mg	once monthly (heartworm prevention) or as directed
50 lbs (22.7 kg)	0.14 mg	0.14 mg	0.27 mg	once monthly (heartworm prevention) or as directed
60 lbs (27.2 kg)	0.16 mg	0.16 mg	0.33 mg	once monthly (heartworm prevention) or as directed
70 lbs (31.7 kg)	0.19 mg	0.19 mg	0.38 mg	once monthly (heartworm prevention) or as directed
80 lbs (36.3 kg)	0.22 mg	0.22 mg	0.44 mg	once monthly (heartworm prevention) or as directed
90 lbs (40.8 kg)	0.24 mg	0.24 mg	0.49 mg	once monthly (heartworm prevention) or as directed
100 lbs (45.4 kg)	0.27 mg	0.27 mg	0.54 mg	once monthly (heartworm prevention) or as directed
120 lbs (54.4 kg)	0.33 mg	0.33 mg	0.65 mg	once monthly (heartworm prevention) or as directed
150 lbs (68 kg)	0.41 mg	0.41 mg	0.82 mg	once monthly (heartworm prevention) or as directed

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

Ivomec 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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Why the Indication Changes the Meaning of the Number

This calculator uses the 0.006 mg/kg standard reference recorded for heartworm prevention. It must not be carried over to mange, ear mites, intestinal parasites, or other uses. Those conditions can involve different routes, schedules, and substantially different dose ranges, so the same dog’s weight can lead to a very different veterinary plan.

Product concentration matters just as much as body weight. A heartworm preventive chew, an injectable livestock solution, and a horse paste are not interchangeable ways to deliver the same number. Concentrated large-animal products make small measuring errors especially dangerous. Breed-related MDR1 sensitivity and interacting drugs can also change the risk without changing the dog’s weight.

Use the result to understand the heartworm-prevention arithmetic and to ask your veterinarian which product and indication apply. Do not use it to convert or dilute a livestock product at home.

How to Give Ivermectin to Your Dog

For heartworm prevention, follow the prescribed product label and ask the clinic what testing is required before starting or restarting it. Dogs with an ABCB1 (MDR1) variant—including some Collies, Australian Shepherds, Shetland Sheepdogs, and related breeds—can be unusually sensitive to higher ivermectin exposures. Discuss breed risk, indication, product, and whether genetic testing is useful with the veterinarian rather than applying one warning to every formulation.

It is generally recommended to give Ivermectin with food to help reduce stomach upset. It may interact with spinosad, ketoconazole, cyclosporine, and P-glycoprotein inhibitors.

Side Effects and Safety

Common side effects include lethargy, decreased appetite, vomiting, and diarrhea. More serious side effects can occur, such as ivermectin toxicity (MDR1 breeds), ataxia, blindness, seizures, and coma.

Cautions · 12

When Ivomec should be used with caution or avoided

Some dogs should not take Ivomec, 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 Ivomec.

MDR1 gene mutation (Collies, Australian Shepherds, Shetland Sheepdogs, etc.)
puppies under 6 weeks
debilitated animals
known hypersensitivity

Interactions · 13

Ivomec drug interactions

Ivomec can interact with other drugs. This list is not complete — always give your veterinarian a full list of your dog's medications and supplements.

spinosad

ketoconazole

cyclosporine

P-glycoprotein inhibitors

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 Ivomec, 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 or loss of coordination
Dilated pupils or apparent blindness
Tremors or seizures
Excessive drooling
Collapse or unresponsiveness

Frequently Asked Questions

Frequently Asked · 07

Questions about this medication

Is ivermectin safe for all dogs?

No. Dogs with the MDR1 gene mutation (common in Collies, Australian Shepherds, Shetland Sheepdogs, and related breeds) can suffer severe, potentially fatal toxicity from ivermectin. A simple genetic test can determine if your dog carries this mutation. At heartworm prevention doses (very low), ivermectin is generally safe for most breeds.

How much ivermectin do I give my dog?

For heartworm prevention, the dose is 6 micrograms per kilogram (0.006 mg/kg) given once monthly. For mange treatment, much higher doses are used (0.3-0.6 mg/kg daily), but these should ONLY be given under direct veterinary supervision due to the risk of toxicity.

What breeds cannot take ivermectin?

Breeds with the MDR1 (ABCB1) gene mutation are at risk. This includes Collies, Australian Shepherds, Shetland Sheepdogs, Old English Sheepdogs, English Shepherds, and mixed breeds with these heritages. However, not all individuals of these breeds carry the mutation — genetic testing is recommended.

What are signs of ivermectin toxicity in dogs?

Signs include excessive drooling, dilated pupils, blindness, tremors, staggering, disorientation, seizures, and coma. Symptoms can appear within 4-12 hours of ingestion. If you notice any of these signs, seek emergency veterinary care immediately.

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 Ivomec. It cannot decide whether this drug, indication, formulation, or schedule is appropriate for an individual animal.

Context in this medication record

Commonly listed uses: heartworm prevention, mange (demodectic/sarcoptic), ear mites, intestinal parasites
Recorded forms: tablet, chewable, injectable, topical
Reference timing: once monthly (heartworm prevention) or as directed; onset 4-12 hours; duration 30 days (heartworm prevention)

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

MDR1 gene mutation (Collies, Australian Shepherds, Shetland Sheepdogs, etc.); puppies under 6 weeks; debilitated animals; known hypersensitivity.

Recorded interactions

spinosad; ketoconazole; cyclosporine; P-glycoprotein inhibitors.

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 Ivermectin — 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 0.006 mg per kg (0.00 mg per lb) of body weight, given once monthly (heartworm prevention) or as directed. 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