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How Long Does It Take a Dog to Digest Heartgard? (Answered)

As bad as heartworm disease is for our canine buddies, it can be prevented with medication. Dogs get exposed to heartworm disease due to the bite of a specific mosquito.

 We often look out for our furry buddies and thanks to Heartgard for playing a huge role in that part. In some regions, heartworm disease is very common and Heartgard is a life savior. But there are some aspects of Heartgard that can be a bit critical for our furry buddies.

So here rises a question. How long does it take for a dog to digest Heartgard? This can be a concern for some people, as some dogs easily get an upset stomach.

If you have similar concerns then you are in the right place. Here you will get all your answers regarding Heartgard and your pup’s ability to digest it.

How long does it take a dog to digest Heartgard?

Usually, it takes a few hours for a dog to digest Heartgard and the time it takes varies from dog to dog. It usually depends on the breed and size of the dog. It can only be given to pups over the age of 6 weeks and it should not take more than a few hours for the dog to digest.

Heartgard comes in a chewable form to prevent your canine buddy from getting exposed to heartworm disease. It has a certain dosage that must be given to the dog with professional advice.

For some dogs, it may take longer to digest the medicine but there is nothing to worry about. Pets have different digestive abilities. They should not be compared with one another.

The ability to digest Heartgard depends on the age and breed of the dog. However, usually, it does not take more than 13 hours for the Heartgard to digest.

It should be in your pet’s system a few hours after chewing. Heartgard is safe for your pup and there should not be much to worry about.

Heartgard works by terminating the germs/parasites living inside and outside the body of your pup. It prevents the germs to form full-grown heartworms and affects your pup’s lungs, heart and veins.

How long does it take for heartworm medicine to absorb?

It can take from 1-4 days for the heartworm medicine to absorb and work properly. It depends on the type of medicine being provided.

For example, Heartgard chewable medicine starts working immediately but it takes 3-5 days for the medicine to terminate off the bacteria inside completely. The worms living outside will be affected immediately.

Milbemycin Oxime is another heartworm medicine that usually takes 1-2 days to work internally and starts working within 24 hours externally.

Again, it depends on the age and breed of the dog and how severely it has been exposed to heartworm disease.

Usually, it should not take more than 2/3 days for the heartworm medicine to get absorbed and start working.

How long does heartworm medicine stay in a dog’s system?

The heartworm medicine stays in a dog’s system for 1-4 days. The active ingredients exit the body after 1-4 days. It may come as shock to some people as heartworm medicine is given monthly. But that’s not how it works.

The active ingredients in the heartworm medicines work by terminating off the bacteria living in the bloodstream for the past 30 days in the dog’s body.

It stays for about 1-4 days and terminates the germs and bacteria that may have been formed over the past 30 days since the last dosage of medication worked. This is why it is given monthly.

Can Heartgard make a dog throw up?

Yes, Heartgard can make a dog throw up. Throwing up is one of the side effects due to the consumption of Heartgard.

There is nothing to worry about if the dog throws up on rare occasions. You can repeat the dosage after a few hours or provide it with a small portion of food.

If the vomiting is repetitive then there is a chance that your dog might be allergic to Heartgard and a different type of heartworm medicine needs to be provided to the dog.

The Heartgard is a tablet that can get stuck to your dog’s throat causing the dog to throw up.

It is also possible that since Heartgard works by terminating off larvae before it forms full-grown heartworms, the Heartgard may cause some slight effect on the dog’s digestive system, making the dog sick or throw up.

However, you need to try a different heartworm medicine or seek professional help if the dog keeps throwing up repetitively, due to the consumption of Heartgard.

What are the side effects of Heartgard?

Like other medications, Heartgard too has some side effects. The severity of the side effect depends on the dog. The medicine may or may not suit your dog. Below provided is a detailed explanation of the side effects that may occur.

Vomiting and diarrhea:

Vomiting and diarrhea are common side effects of Heartgard which occur on rare occasions. It does not certainly mean the pet is allergic to Heartgard.

Dogs may throw up if the tablet gets stuck in their throat or due to long-term effects on their digestive system due to terminating the larvae.

Depression, lethargy, and anorexia:

On rare occasions, the dog may get diagnosed with depression, lethargy, or anorexia.

These are not allergic reactions so there is not much to be worried about. Chances are very low for these to occur if proper dosage is given.

Itching, hives, swelling of face, and seizures:

These are allergic reactions. If your dog is allergic to Heartgard or given a high dosage than usual it can be diagnosed with these. Contact your vet immediately if your dog is showing signs of allergy.

Mydriasis, ataxia, staggering, convulsions, and hypersalivation:

If the proper dosage is not given the dog may be diagnosed with mydriasis, ataxia, staggering, convulsions, and hypersalivation on rare occasions. Seek professional help if needed.

How long do Heartgard side effects last?

It depends on the severity of the side effect. Normal side effects may last about a week or so. However, it depends on your dog’s age and strength. Normal reactions such as vomiting, diarrhea, and lethargy can last up to a week under treatment.

However, if the dog is diagnosed with severe side effects then the dog’s ability to fight the disease plays a vital role in how long it can last along with the treatment being provided.

It is always wise to seek professional help due to the side effects only then you can be sure about the severity and duration of side effects.

The side effects are not visible immediately. It can take up to 24 hours for the side effects to show. Keep your dog under observation if Heartgard is given for the first time.

How does Heartgard work?

The process using which Heartgard works is explained below.

Combines two medicines:

Heartgard combines two medicines to form a tablet that acts as a shield against three types of common parasites that affect our canine buddies. 


Heartgard enters the body of the dog in the form of a tablet and gets dissolved inside. It starts working by terminating the external parasites living in the dog’s body within 24 hours of consumption.

Terminating off the larvae:

Heartgard works by terminating off the larvae before it forms full-grown heartworm inside the body of pets. The active ingredients work for 2-4 days and clean the bloodstream of the past 30 days that may have been exposed to bacteria and parasites.

Keep in mind that Heartgard cannot terminate a fully grown heartworm.

Is a second dose safe if my dog throws up the first Heartgard dose?

Yes, it is safe to give the dog a second dosage after throwing up. There are various reasons why dogs might throw up rarely after the consumption of Heartgard.

The second dose should be given a few hours after. It can be given with a small portion of food for the dog to swallow without understanding. However, if vomiting does not stop then the dog might be allergic to Heartgard.

What if my dog ate extra Heartgard?

It depends on how much extra your dog has consumed. If the dosage is consumed four times extra than the usual amount then your vet may be able to get the dog to vomit immediately.

Extra dosage of Heartgard can cause severe side effects. It should not be taken lightly.

Final thoughts

To sum it up, it normally takes a few hours for the dog to digest Heartgard. It should not take more than 13 hours. However, it solely depends on the age and breed of the dog. If vomiting occurs on rare occasions, the dosage should be repeated in several hours.