5 Best Heartworm Prevention Medications for Dogs in 2026, Recommended by Vets

Heartworm disease is caused by a parasite spread by mosquito bites that travels through the bloodstream and settles in a dog’s heart and lungs. As the worms grow, they can damage these organs and cause coughing, trouble breathing, fatigue, and, in severe cases, heart failure. 

The dangers of heartworm disease, the lengthy and complex treatment process, and the high cost of care make prevention the safest and most effective defense. Heartworm disease has been diagnosed in all 50 U.S. states and in many countries worldwide, and any dog exposed to mosquitoes is at risk. When given consistently and as directed, veterinarian-recommended preventives are highly effective at protecting dogs from this serious and potentially life-threatening disease. 

The best heartworm medications for dogs are not only effective but also easy to administer on schedule and appropriate for your pup’s age, weight, and health considerations.  

Because heartworm medicines come in several forms and contain different active ingredients, our panel of veterinarians selected their choices for the best heartworm prevention for dogs to help simplify your shopping process. Don’t forget to speak with your vet before choosing one—heartworm prevention medication for dogs is available by prescription only, and your vet can help you determine the best option for your pet’s individual needs. 

What To Consider When Buying Heartworm Prevention Medication for Dogs 

When looking at various heartworm preventions for dogs, think about the following factors. 

Veterinarian Input 

You should always get input from your veterinarian for dog heartworm medication for several reasons.  

First, you must get a prescription from your veterinarian, as heartworm preventives contain ingredients that must be administered in the correct dosage to be safe and effective, which is why they are all regulated by the FDA.  

Second, your pup must have an up-to-date heartworm test on file with your veterinarian before receiving heartworm prevention medicine,  as it doesn’t kill adult heartworms, only immature larvae.  

Third, our veterinary panel advises pet parents to discuss with their veterinarian which heartworm medication is appropriate for their individual dogs’ unique needs, particularly dogs who have a history of seizures, the MDR1 mutation, or sensitivities to certain flavors/proteins. 

Scope of Coverage  

Consider whether you want broad parasite protection or just heartworm prevention. Talk to your veterinarian about which parasites pose the biggest risk to your dog depending on where you live and your dog’s lifestyle. Taking one pill that protects against heartworm disease, fleas and ticks, and intestinal parasites may be the right health decision for your dog. 

Form of Treatment  

The best heartworm medicines for dogs come in three forms—tablets, chews, or topical treatments—and are typically administered monthly. Choose the right one for you and your dog depending on lifestyle and ease of administration. These medications must be given according to the manufacturer’s dosage recommendations to be effective.  

If your dog doesn’t like tablets or chews or is sensitive to flavors/proteins the medication may contain, then a topical solution may be best. If your dog needs frequent baths, then an oral solution may be a better choice, since frequent baths may diminish the efficacy of certain topical medications. 

Dog’s Age, Size, and Health 

Dog heartworm medications are safe and effective at the correct dosage, which is determined by your dog’s age and weight. Some drugs, such as those in the isoxazoline class, may not be suitable for dogs with certain health issues, like seizures or neurological disorders. Your veterinarian will recommend the best dog heartworm medicine for your dog’s age, size, and health.