Heartgard for Dogs: A Complete Guide to Heartworm Protection

Heartworm disease is one of the most dangerous yet preventable health threats in dogs. Transmitted through mosquito bites, heartworms can silently grow inside your dog’s heart and lungs, leading to organ damage, breathing problems, and even death if left untreated. Fortunately, a simple monthly chew like Heartgard for Dogs can protect your canine companion from this life-threatening condition.

In this guide, we’ll explain what Heartgard is, how it works, benefits, dosage instructions, safety tips, and frequently asked questions to help you make an informed decision for your pet’s health.

What Is Heartgard for Dogs?

Heartgard is a monthly heartworm preventive medication available in a chewable tablet form. Most commonly available as Heartgard Plus, it contains:

Ivermectin – Kills heartworm larvae before they mature.

Pyrantel – Eliminates common intestinal worms like roundworms and hookworms.

It is FDA-approved, vet-recommended, and suitable for dogs of all breeds when used as directed.

How Does Heartgard Work?

Dogs can’t tell you when they’re bitten by mosquitoes, making heartworm infections difficult to detect until it’s too late. Heartgard works by killing immature heartworm larvae (called microfilariae) before they can develop into adult worms.

By giving one chew every 30 days, you break the infection cycle and ensure continuous protection.

Key Benefits of Using Heartgard for Dogs

✔️ Prevents deadly heartworm disease

✔️ Protects against roundworms and hookworms

✔️ Flavoured chewable—easy to feed like a treat

✔️ Suitable for puppies and adult dogs

✔️ Safe when used long-term under veterinary guidance

Most dogs love the meaty taste, making it stress-free for pet parents to administer.

When Should Dogs Start Taking Heartgard?

Puppies can start Heartgard as early as 6 weeks of age, provided they are healthy.

For adult dogs, if they have never taken heartworm preventives before, it’s strongly recommended to get a heartworm test before starting Heartgard. This ensures your dog is free from existing infection.

Heartgard Dosage Guide

Heartgard is dosed based on your dog’s body weight. It is usually available in three weight categories:

Dog Weight Heartgard Chew Variant

Up to 11 kg (25 lbs) Small Dog

12–22 kg (26–50 lbs) Medium Dog

23–45 kg (51–100 lbs) Large Dog

🔹 Give one chew every month, on the same date.

🔹 Can be given with or without food.

🔹 If your dog spits it out, ensure they eat the full dose.

What If You Miss a Dose?

Life happens. If you forget a dose:

Give it as soon as you remember.

Do not double dose.

If more than two months have passed, consult your vet and schedule a heartworm test before continuing.

Consistency is key—setting a reminder on your phone can help avoid gaps in protection.

Are There Any Side Effects?

Heartgard is generally very safe, but like any medication, mild reactions may occur in rare cases, such as:

Vomiting

Diarrhoea

Lethargy

Drooling

Dogs with the MDR1 gene mutation (common in Collies, Australian Shepherds, Shetland Sheepdogs, etc.) may be more sensitive to ivermectin. Speak to your vet if your dog belongs to a sensitive breed.

Heartgard vs Other Heartworm Preventatives

Brand Format Additional Protection Frequency

Heartgard Chewable Roundworms, Hookworms Monthly

NexGard Spectra Chewable Fleas, Ticks, Intestinal Worms & Heartworm Monthly

Revolution Topical Fleas, Mites & Heartworm Monthly

ProHeart Injection Injection Heartworm Only Every 6–12 Months

Heartgard is ideal if you prefer a simple and trusted heartworm-only + deworming solution, while broader-spectrum products exist for all-in-one protection.

Frequently Asked Questions

1. Can I give Heartgard to pregnant or nursing dogs?

Yes, Heartgard is considered safe for breeding, pregnant, and lactating dogs when used under veterinary supervision.

2. Can Heartgard treat existing heartworm infection?

❌ No. It only prevents new infections. Dogs with existing heartworm disease require specialized treatment at a veterinary clinic.

3. Can indoor dogs skip Heartgard?

No. Even indoor dogs can be bitten by mosquitoes that enter through open doors or windows. Prevention is much safer and cheaper than treatment.

4. Do I need a prescription to buy Heartgard?

In most regions, yes, a veterinary prescription is required to ensure safe use.

Final Thoughts: Is Heartgard Worth It?

Absolutely. Heartworm is a deadly but preventable disease, and one chew a month is all it takes to protect your dog. Heartgard for Dogs is trusted, affordable, and easy to administer — making it an excellent choice for responsible pet parents.

Whether you have a tiny puppy or a senior dog, heartworm prevention should be a lifelong routine. Consult your veterinarian to confirm the right dosage and ensure year-round protection.