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PetDosageChart

Antiparasitic combination · For Dogs

How much Heartgard Plus (Ivermectin / Pyrantel) can I give my dog?

Standard Heartgard Plus dose for dogs is 0.006 mg per kg (0.00 mg per lb), given once monthly. Use the calculator below for your dog's exact weight, or jump to the weight-by-weight chart.

Onset
N/A (preventive)
Duration
30 days
Class
Antiparasitic combination

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

Heartgard Plus dose by dog weight

Pick your dog's weight to jump to a dedicated page with the dose, frequency, safety notes, and FAQ for that size.

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Dosage Chart · 02

Heartgard Plus dosage for dogs by weight

Scroll sideways to see full table

Weight Low Dose Standard Max Safe Frequency
5 lbs (2.3 kg) 0mg 0mg 0mg once monthly
10 lbs (4.5 kg) 0mg 0mg 0mg once monthly
15 lbs (6.8 kg) 0mg 0mg 0mg once monthly
20 lbs (9.1 kg) 0mg 0mg 0mg once monthly
25 lbs (11.3 kg) 0mg 0mg 0mg once monthly
30 lbs (13.6 kg) 0mg 0mg 0mg once monthly
40 lbs (18.1 kg) 0mg 0mg 0mg once monthly
50 lbs (22.7 kg) 0mg 0mg 0.5mg once monthly
60 lbs (27.2 kg) 0mg 0mg 0.5mg once monthly
70 lbs (31.7 kg) 0mg 0mg 0.5mg once monthly
80 lbs (36.3 kg) 0mg 0mg 0.5mg once monthly
90 lbs (40.8 kg) 0mg 0mg 0.5mg once monthly
100 lbs (45.4 kg) 0.5mg 0.5mg 0.5mg once monthly
120 lbs (54.4 kg) 0.5mg 0.5mg 0.5mg once monthly
150 lbs (68 kg) 0.5mg 0.5mg 1mg once monthly

Common Uses · 03

What is Heartgard Plus (Ivermectin / Pyrantel) used for in dogs?

heartworm prevention roundworm treatment hookworm treatment

Administration · 04

How to give Heartgard Plus to your dog

Give Heartgard Plus on the same day each month, year-round. It is a beef-flavored chewable that most dogs eat willingly. A heartworm test is required before starting. At the very low doses used in Heartgard, ivermectin is generally safe even for most MDR1-positive breeds, but consult your vet.

Available Forms

chewable tablet

Give with Food?

Yes — give with food

Side Effects · 05

Side effects of Heartgard Plus in dogs

Common side effects

vomiting
diarrhea
decreased appetite
lethargy

Serious side effects — call your vet

  • allergic reaction
  • tremors (rare)
  • seizures (rare, MDR1 breeds at higher doses)

Emergency · 06

When to call the vet

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

  • Vomiting within 1 hour of dosing
  • Your dog misses more than one monthly dose
  • You moved from a non-endemic to an endemic heartworm area
  • Any neurological signs (tremors, incoordination)
  • Your dog tests positive for heartworm

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 Ivermectin / Pyrantel.

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 0.006 mg per kg (0.00 mg per lb) of body weight, given once monthly. 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

Is Heartgard enough for my dog?
Heartgard Plus prevents heartworm and treats roundworms and hookworms, but it does NOT protect against fleas, ticks, or other external parasites. Most dogs need a flea/tick preventive (like NexGard) in addition to Heartgard. Your vet can recommend a complete parasite prevention plan.
What happens if I miss a month of Heartgard?
If you miss one month, give the dose as soon as you remember and resume the monthly schedule. If you miss more than one month, contact your vet — your dog may need to be tested for heartworm before restarting, as the preventive only kills larvae acquired in the previous 30 days.
Can I give Heartgard to Collies?
Yes. At the very low ivermectin doses used in Heartgard (6 mcg/kg), it is considered safe for Collies and other MDR1-positive breeds. The ivermectin toxicity risk in these breeds occurs at much higher doses (300+ mcg/kg), far above what Heartgard contains.
Does my dog need Heartgard year-round?
The American Heartworm Society recommends year-round heartworm prevention in all areas. Even in colder climates, unpredictable warm spells can allow mosquitoes to transmit heartworm. Year-round prevention is the safest approach.

Safety · 10

More resources