How Long Does It Take A Dog To Digest Heartgard?

The majority of dogs will get infected with heartworm disease at some point in their lives. It isn’t a matter of ‘if’ but more a matter of ‘when’.

Heartworm disease is caused by parasitic worms or the heartworm in this case.

Do not fret, with proper medication, this pesky parasite can be eradicated for good.

One popular medication for heartworms in dogs is Heartgard.

In this post, we’ll explore more about Heartgard, unravel the mystery of digestion and shed light on what this means for your ‘s dog’s protection.

What Is Heartgard?

Heartgard is a heartworm medicine that is to be taken orally by your dog. It is effective for treating heartworms and can only be prescribed by a vet.

There is also Heartgard Plus that treats both heartworms and intestinal parasites like hookworms and roundworms.

Depending on your dog’s current condition, the vet will prescribe the more suitable type of Heartgard.

How Does Heartgard Work?

Heartgard contains the active ingredient Ivermectin which is effective at eradicating a broad range of parasites.

The aim of Heartgard is to finish off the larvae of the heartworm before they have the chance to mature into adults and breed.

Once these larvae die off, they will start to decompose and get reabsorbed into the dog’s body.

How Long Does It Take A Dog To Digest Heartgard?

It doesn’t take long for your dog to fully digest the Heartgard pill, about 2-8 hours for the majority of dogs.

How Long Does Heartgard Stay In A Dog’s System?

The active ingredient ivermectin has a half-life of two days. Once the dog is able to fully digest Heartgard, it will remain active and effective in your dog’s body for three to four days.

Each dose of Heartgard can protect your dog for up to thirty days. After which the effectiveness will start to drop.

How Long Does It Take For Heartgard To Work?

The medicine has an immediate effect on the heartworm larvae once your dog consumes the tablet.

It should take about three to five days to remove most of the heartworms.

Is Heartgard Safe For My Dog?

Heartgard is generally safe for most dogs including pregnant and breeding dogs.

Studies have shown that even when given 10 times the recommended dose of Heartgard, it was still safe for the dogs who took it.

How Much Heartgard Should I Give My Dog?

gave my dog wrong dose of nexgard

This heartworm pill comes in three different doses that correlate to the weight of your dog. The weight groups are:

  • Up to 25 lbs (Blue)
  • 25 lbs to 50 lbs (Green)
  • 50 lbs to 100 lbs (Brown)

For dogs that weigh over 100 lbs, you will have to mix and match the different dosages.

Please note that this heartworm pill contains an active ingredient that can be toxic to your dog if given the wrong dosage.

So you will have to be sure of your dog’s weight before giving your dog Heartgard.

Your dog needs to be at least six weeks of age before it can start taking the Heartgard medicine.

Heartgard is made to be palatable to dogs and it tastes like beef. The proper way to consume it is for your dog to chew it rather than swallow it whole.

A good way is to break up the tablet into your dog’s food and let your dog eat it all up.

What If A Dog Throws Up After Taking Heartworm Medication?

The most common side effects after 24 hours for dogs that took Heartgard were diarrhea and vomiting.

DO NOT give your dog another dosage thinking that the tablet was not properly absorbed.

Get the clearance from your vet before doing so.

However, this was only shown in a very small percentage of the dogs that took it.

The other known symptoms are:

  • Lethargy
  • Excess salivation
  • Convulsions
  • Lack of appetite
  • Dilated pupils

If the side effects do not clear up after a day, please consult your vet.

What Is The Difference Between Nexgard And Heartgard?

Nexgard and Heartgard are both anti-parasitic medications that are made by the same company.

Nexgard is more effective against parasites like fleas and ticks which are common in dogs.

This is due to the fact that dogs spend a lot more time outdoors playing and going for works.

Therefore the risk of infection is a lot higher.

The dosage for Nexgard is similar to Heartgard which is according to the dog’s weight.

It can be possible to give your dog the wrong dosage of Nexgard if you have several different-sized dogs at home.

What Are Heartworms?

If your dog has yet to get heartworms, it is important to know what it is as it can be fatal to dogs in serious cases.

For dog owners whose dogs have gotten heartworms before, there is always a possibility of getting reinfected.

This parasitic worm got its name from the fact that it prefers to reside in a dog’s heart. It is unlikely to find heartworms anywhere else in the dog’s system.

Female heartworms can grow up to 14 inches long and 1/8 of an inch wide. Male heartworms are about half the size.

The scary fact is that dogs with heartworm disease can have more than 300 heartworms in their hearts.

How Do Heartworms Spread?

Not many dog owners are aware that heartworms are actually spread via mosquitoes. More than 30 mosquito species can spread heartworm disease to dogs.

There’s usually an uptick in heartworm infections during mosquito breeding season. But if you live in tropical countries, the threat of mosquitoes can be year round.

Cats can get heartworms from mosquitoes too so keep your feline friend safe from mozzies as well.

When an infected female mosquito bites a dog to feed, the heartworm larvae in her system will be transmitted into the dog’s system.

What Is The Life Cycle Of A Heartworm?

The heartworm larvae will first start to develop in the female mosquito’s body for 10-30 days.

When a dog gets bitten by a mosquito, the larvae will travel along in the dog’s blood vessels and lodge themselves in the heart.

These heartworms will then start to grow, mate and produce numerous heartworm larvae in the dog’s heart.

What Damage Can Heartworms Do To Dogs?

Adult heartworms can clog up the major blood vessels of the heart. They can also prevent the valves of the heart from functioning properly.

When the major vessels are clogged up, this prevents adequate blood supply from reaching the other parts of the dog’s body and major organs like the liver, lungs and kidneys.

The lack of blood flow to these organs can cause them to fail.

Symptoms Of Heartworms Disease In Dogs

If your dog has a heartworm infection, here are some common symptoms that it will exhibit.

  • Difficulty in breathing
  • Pale gums and lips
  • Coughing
  • Wheezing
  • Lack of energy

In more serious cases, some dogs can even faint and become unconscious.

How To Prevent Heartworms In Dogs?

Heartworm prevention in dogs is a rather difficult one to pull off given the nature of transmission.

As careful as we are, it is rather impossible to completely prevent mosquitoes from biting your dog.

You can employ preventive measures like mosquito repellants, nets and keep doors and windows closed.

It is not possible to keep your dog indoors 24/7 like a cat. Your dog still needs to go out for walks and exercise.

The best way to keep heartworm disease at bay is through the regular and appropriate usage of heartworm medication.


When it comes to heartworms, prevention is key to stopping your dog from getting any heart problems due to heartworms.

I understand from a number of dog owners that there are wary of giving their dogs such medication which contains a very strong active ingredient.

The best way around this is to have a good talk with your local vet and clear whatever doubts you might have.

Do remember that heartworm disease can be deadly if left untreated.

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