Heartgard Unflavored Tablets for Dogs, up to 25 lbs, 6 treatments (Blue Box)

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Your furry friend must have a current heartworm test result on file with your veterinarian in order to be prescribed heartworm medication. Please visit your veterinarian to have this test performed annually to protect your four-legged friend. Heartgard Unflavored tablets for dogs is a heartworm preventative that kills heartworms. Given monthly, it comes in a chewable, unflavored tablet that is easily pilled or disguised in food.


To prevent heartworm disease by eliminating the tissue stage of heartworm larvae (Dirofilaria immitis) for one month (30 days) after infection.

Possible Side Effects

The following adverse reactions have been reported following the use of Heartgard: Depression/lethargy, vomiting, anorexia, diarrhea, mydriasis, ataxia, staggering, convulsions and hypersalivation.

Drug & Food Interactions

Talk to your veterinarian about any other drugs your pet is taking before starting this medication.


All dogs should be tested for existing heartworm infection before starting treatment with Heartgard (ivermectin) Tablets, which is not effective against adult heartworm. Infected dogs must be treated to remove adult heartworms and microfilariae prior to initiating a program with Heartgard. While some microfilariae may be killed by the ivermectin in Heartgard at the recommended dose level, Heartgard is not effective for microfilariae clearance. A mild hypersensitivity-type reaction, presumably due to dead or dying microfilariae and particularly involving a transient diarrhea, has been observed in clinical trials with ivermectin after the treatment of some dogs that have circulating microfilariae. Keep this and all drugs out of the reach of children. In case of ingestion by humans, clients should be advised to contact a physician immediately. Physicians may contact a Poison Control Center for advice concerning cases of ingestion by humans.

Dosage Chart

Color on BoxWeight RangeStrengthDosageProduct Page
BlueUp to 25 lbs 68 mcg Ivermectin per tablet Administered orally at monthly intervals✓-Click Here
Green26 to 50 lbs136 mcg Ivermectin per tabletAdministered orally at monthly intervals✓-Click Here
Brown51 to 100 lbs272 mcg Ivermectin per tabletAdministered orally at monthly intervals✓-Click Here
  1. Prescribing Information

See all items by Heartgard

  • Item Number
  • Dosage Measure
    Use according to your veterinarian's instructions.
  • Common Brand Name(s)
  • Generic Name
  • For Use With
    Dogs - 6 weeks or older
  • Brand
    Boehringer Ingelheim, Merial
  • Breed Size
    Extra Small & Toy Breeds, Small Breeds
  • Lifestage
    Puppy, Adult, Senior
  • Product Form
    Chewable Tablet
  • Strength
    68 mcg Ivermectin pet tablet
  • Health Condition
  • Drug Type

Active Ingredients: Ivermectin (68 mg)

Recommended Dosage

The Heargard tablet should be given so that dogs swallow the whole tablet. (The tablet may be wrapped in food to encourage consumption.) Care should be taken to see that the dog consumes the complete dose, and treated animals should be observed for a few minutes after administration to ensure that part of the dose is not lost or rejected. If it is suspected that any of the dose has been lost, redosing is recommended.

Storage Instructions

Store at controlled room temperature 68°-77°F degrees Fahrenheit.


What is heartworm disease?

Heartworm disease in dogs (dirofilariasis) is a serious and potentially fatal disease. Heartworms spend their adult lives in the pulmonary arteries. The adult worms can cause lasting damage to the heart, lungs and arteries.

How do dogs get heartworms?

Heartworms are transmitted from one dog to another by mosquitoes, which pick up tiny immature heartworms, called microfilariae, when they bite an infected dog. Larvae develop and are then transmitted to another dog when that dog is bitten by the infected mosquito.

Where are dogs at risk for heartworm infection?

All dogs are at risk for heartworm disease, no matter where they live heartworms don't discriminate based on geography. In the past, heartworm disease in the United States was primarily limited to the South and Southeast regions. However, it is now found in all 50 states, in Canada, and is spreading to new areas each year. The American Heartworm Society notes that uncared-for dogs and certain wildlife can be carriers of heartworms. Mosquitoes blown great distances by the wind and the transportation of infected pets to different geographic locations can all contribute to the spread of heartworm disease.

What are the signs of heartworm infection?

Signs of heartworm disease can be subtle and difficult to detect until its later stages. As the disease progresses, signs begin to appear. Contact your veterinarian immediately if you notice coughing, difficulty breathing, sluggishness and less energy for exercise in your dog. Adult heartworms cause serious harm to your dog's heart, lungs and certain internal organs. Left untreated, heartworm disease can result in loss of consciousness and death.

How are dogs tested for heartworm infection?

The most common method for heartworm testing is for a veterinarian to collect a small blood sample from a dog and evaluate the sample using a specialized test kit to detect the presence of adult heartworms.

How can heartworm disease in dogs be prevented?

Pet owners can use Heartgard (ivermectin), the #1 veterinarian-recommended preventive on the market to help prevent heartworm disease. Heartgard kills tissue larval stages of heartworms and helps prevent them from developing into adults and causing heartworm disease. In an unprotected dog, heartworm larvae mature into adults and ultimately migrate to the arteries of the lungs.

How long do I have to give my dog Heartgard?

Monthly use of Heartgard is essential because it cannot be determined with certainty when the threat of mosquitoes has passed. Talk to your veterinarian for dose and regimen recommendations.

Can heartworm disease be treated?

Although it is possible to treat heartworm disease if a dog becomes infected, it is difficult, expensive and risky, particularly in dogs that have begun to exhibit clinical signs of infection.

What if my dog becomes infected with heartworms?

There are treatment options available to kill adult heartworms in dogs that have become infected. Treating dogs with heartworm disease starts with a thorough physical examination by the veterinarian. The veterinarian will then discuss treatment options with you. Typically, the dog is hospitalized during the treatment period. Because there is a risk of blood clots or worm debris blocking blood vessels from adult heartworm treatment, the dog must then remain quiet in close confinement for another 4 to 6 weeks after treatment. A second round of treatment may be required for some dogs. The veterinarian may also give your dog a treatment to rid it of the immature larvae that are circulating through the blood stream.

Can my dog "get" heartworm disease directly from an infected dog?

No, the way dogs become infected is via a bite from a mosquito that is carrying heartworm larvae.

Are nursing puppies immune to heartworm disease if the mother is receiving Heartgard?

No. Puppies that are nursing may become infected. Heartgard can be used in puppies as young as 6 weeks of age and puppies benefit from the ability of Heartgard to treat and control roundworms and hookworms.

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  • 4 out of 5 stars

    Tablets vs Beef Chew

    By on

    I have two Yorkies. My male dog, Bam Bam, loves the beef chews and my female hates them. I purchased the tablet for little Pebbles and although I can get it into her a bit easier than the beef chew, I was hoping the tablet would be just a bit smaller so that I could disguise it somewhat. I am very thankful that Heartgard makes these tablets and will continue to use them going forward. A big SHOUT OUT to for their continued wonderful service and love of our animal friends.

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  • 5 out of 5 stars

    Great product great service

    By on

    We are very happy with our purchase of unflavored heart worm tabs via .. our dog is insanely picky he would not touch other brands of flavored chews even when we tried to hide them .. these small unflavored tabs are perfect to hide in a piece of meat and eaten in 1 second without issue .. a lifesaver for us and our pup. Chewy made it easy contacting my vet and shipped quick and efficiently. Will be ordering more and stocking up Incase they discontinue.

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  • 5 out of 5 stars

    No allergic reaction

    By on

    My poor little Jack Russell has had many problems with heartworm prevention medicine until are vet recommended the original heartgard. Thankfully he's had no problems whatsoever taking this medication and I am so happy

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  • 5 out of 5 stars

    Hard to Find - Thanks Chewy!

    By on

    Most of the heartworm meds have additional ingredients that my dog can't tolerate. This is the only product I have found that just addresses heartworms. It hasn't caused any seizures and he has less stomach issues than anything else I have tried.

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  • 5 out of 5 stars

    I love chewy

    By on

    I love chewy. I’ve been using these tablets for a long time, and as far as I know my dogs haven’t had any adverse reactions to them.

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