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BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We only make money if you purchase a product through our links, and all opinions about the products are our own. Read more  
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We buy all products with our own funds, and we never accept free products from manufacturers.Read more 
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Why trust BestReviews?
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We only make money if you purchase a product through our links, and all opinions about the products are our own. Read more  
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We only make money if you purchase a product through our links, and all opinions about the products are our own. Read more  
BestReviews spends thousands of hours researching, analyzing, and testing products to recommend the best picks for most consumers. We buy all products with our own funds, and we never accept free products from manufacturers.Read more 
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We purchase every product we review with our own funds — we never accept anything from product manufacturers.

51 Models Considered
8 Hours Researched
2 Experts Interviewed
60 Consumers Consulted
Zero products received from manufacturers.

We purchase every product we review with our own funds — we never accept anything from product manufacturers.

Buying guide for best dog heartworm medications

If you get a mosquito bite, it can cause anything from an itchy bump to a dangerous disease like West Nile virus. The same goes for dogs. Sometimes, a mosquito bite causes a mild skin reaction in a dog, but other times it can cause heartworm. Giving your dog heartworm medication protects your pet from this deadly disease.

How does heartworm occur in dogs? It starts with a bite from a mosquito carrying heartworm larvae. The larvae travel via the bloodstream near the dog’s heart and lungs, where they mature into adult worms. In turn, the dog may suffer organ damage, lung disease, and even heart failure. It’s important to kill the larvae before they mature by giving the dog a monthly heartworm medication.

We’ve put together this buying guide with some of the key information you need to understand regarding heartworm medications for dogs so you can make the right choice. We’ve highlighted some of our top picks, too.

dog heartworm med1
Some veterinarians draw blood to test the dog for heartworm during its annual checkup.

Key considerations

Side effects

Some of the side effects associated with heartworm medication include nausea, vomiting, loss of appetite, seizures, and tremors. Some dog owners report that their dogs experience mild or brief side effects after taking heartworm medication. It’s very important to give your dog the right dosage of heartworm medication to reduce the chances of side effects.

If your dog already has an adult heartworm infestation, giving the dog one of these preventive medications could cause side effects or a more serious health problem.

Additionally, certain breeds may be more sensitive to certain brands of heartworm medication. Always check with your veterinarian about any concerns regarding the potential side effects.

Dose

Manufacturers recommend that you give your dog heartworm medication monthly based on the weight of the animal. And don’t just guess at the dog’s weight. Too large a dose can lead to dangerous side effects; too small can be ineffective. Make sure your veterinarian weighs your dog at each appointment. 

If it’s been a while since your dog has been to the vet, schedule an appointment before you begin giving your pet heartworm medication. The veterinarian will also want to test your dog for an active heartworm infestation.

Manufacturers use a weight range for the optimum dosage for heartworm medications, for example, 10 to 20 pounds, 20 to 40 pounds, or more than 75 pounds. The heartworm medication you use may have different weight range recommendations. Always follow the dosage instructions on the medication’s packaging.

Most heartworm medications require that you visit your dog’s veterinarian first to obtain a prescription. Occasionally, you may find some that are made to be sold over the counter (without a prescription), but this is rare.

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Features

The biggest differences between heartworm medications are formula (oral or topical) and palatability.

Topical formula

Some heartworm medications are applied topically rather than ingested. These come as a liquid that's applied to the animal's upper back. Some of these medications also guard against ticks and fleas

Note that these liquids can be dangerous for humans to touch or for the animal to ingest. Take care that the dog doesn’t lick the application area and that kids don’t pet the dog in the application area for at least a few hours.

Palatability

Chewable tablets are the most common delivery method for this type of medication. Chewables have a soft consistency, almost like a cube of cheese. The dog should be able to chew it easily, but the tablet shouldn’t crumble like a hard treat, so the dog receives the full dosage.

Chewable heartworm medications have a taste and smell that most dogs love, usually beef, which means they’re more liable to eat it. Of course, some dogs won’t like it, but this type of medication delivery works successfully for most dogs.

Pay attention to the dosing instructions for your particular medication, because it may recommend breaking the chewable into smaller pieces if your dog tends to swallow treats like this whole without chewing them.

dog heartworm med2
DID YOU KNOW?
Without treatment, a heartworm can live in a dog’s heart for up to seven years, although the dog could die before that length of time.
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Accessories

Flea and tick medication: Trifexis Chewable Tablets for Dogs
Along with heartworm medication, dogs need protection against flea and tick infestations. This prescription formula delivers strong performance with minimal side effects.

Dewormer: Merck Animal Health Panacur C Canine Dewormer
Dogs can get hookworms or tapeworms, so using a dewormer medication as needed is important for the animal’s health. The biggest benefit of this dewormer is its ability to handle a variety of parasites while being easy to use.

Glucosamine: Vet Pro Complete Maximum Strength Glucosamine Soft Chews
For dogs with hip and joint problems, giving the animal a regular dose of glucosamine can help the dog move more freely. VetPro Complete packs more glucosamine into each chew, meaning your dog needs fewer doses.

Probiotics: Purina FortiFlora Canine Nutritional Supplement
Regular doses of probiotics can aid your dog’s digestion, which can help the animal’s overall health. Dogs like the taste, so you can sprinkle FortiFlora over food to simplify dosing.

Dog heartworm medication prices

Although some dog heartworm medications seem expensive, using these preventive treatments is far less expensive than treating an animal with heartworm. 

Manufacturers typically sell these medications in multidose packages, commonly 6 or 12, but some brands come in packs of 3. To compare prices from one brand to another, it’s helpful to calculate the price per dose. You’ll typically save a little by choosing a 12 pack over a smaller pack. Also, medications for small dogs cost less than those for bigger dogs. The following are prices for brand-name medications. If you choose a generic, you can expect to pay about half as much as the prices listed here.

Small dogs: $8 to $20 per dose

Medium dogs: $9 to $22 per dose

Large dogs: $10 to $25 per dose

Certain types of heartworm medications also kill other types of immature worm infestations, including hookworm, whipworm, and roundworm.

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Tips

Manufacturers try to create medications that taste good to dogs, but if your dog won’t take it, here are some tips to make the medicine go down more easily.

  • Cover the tablet with peanut butter. Put it on a small piece of bread and your dog won’t even notice the medicine.
  • Put the medicine in a pill pocket. These soft chews have a little hole for inserting a tablet. 
  • Hide the medicine in a favorite treat. If your dog loves hot dogs or cheese cubes, try hiding the tablet inside this special treat.
  • Give the pill when your dog is hungry. Your dog may be more willing to take the medicine in a treat just before mealtime.
  • Train the dog to receive a daily treat. Give your dog the same treat at the same time every day. That way, your dog won’t notice when you add medication to it. 
dog heartworm med3
Most heartworm medications for dogs are safe for dogs six weeks and older.

FAQ

Q. What are some signs that a dog has heartworm?

A. Oftentimes, the signs of heartworm don’t show up until the animal is quite ill. Some of the signs you may notice include unexpected weight loss, lack of energy, persistent cough, swelling in the chest, swelling in the abdomen, and decreased appetite.

Q. Can I use these medications if my dog has heartworm?

A. No. These medications are meant to prevent the larvae from growing into adult worms. Once the dog has a heartworm infestation, it’s too late for these types of medications to work. Consult your veterinarian for a treatment plan. Unfortunately, an adult heartworm infestation can be fatal.

Q. How common are mosquito bites in dogs?

A. A dog’s fur provides some protection from mosquito bites. However, areas on the dog’s body with less fur or where the skin is exposed, such as the ears, nose, and eyes, are vulnerable to mosquito bites. Remove any stagnant water around your home and regularly change the water in any outdoor pet bowls to prevent mosquito eggs from hatching.

Q. Do I need to give my dog heartworm medication in the winter?

A. Veterinarians often recommend using these medications year-round, because it’s impossible to predict when the first or last mosquitos of the season will appear. However, in cold climates, where no insects are present in the winter, skipping a few months of treatment has low risk. In warmer climates where freezing temperatures are rare, skipping treatments is not recommended.

 

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