Is It Okay To Give Heartgard Early? [Vet Advice]

Heartworm disease is one of the worst fears for dog lovers. Dogs are natural hosts for heartworms and are likely to be infested with these parasites. As a result, many people turn to preventive measures.

Although the common period for each dose of heartworm medication is 30 days, with our busy schedules, there may be times when you wonder if it’s okay to give it earlier than that.

The good news is that it’s okay to give heartworm medication to your dog early. Although it should be given on the 30th day, it’s okay to give it earlier, such as on the 25th or 21st day.

Heartworm medication kills the larvae stage of the heartworm, so it’s okay to give it before 30 days as it won’t last that long in your dog’s body. Additionally, heartworm pills only stay in your dog’s system for 24 to 48 hours.

So, can you give heartworm medicine earlier than the norm? What happens when you do that? How long will it stay in the body? Do you have to give it every month? What are the essential things to be aware of? Stay with me, and let’s find out together!

Can I give dog heartworm medicine early?

Heartworm disease is a tragical disease that can claim your beloved pet’s life. So prevention is essential! When you start giving the pill, it should be administered every 30 days.

But what happens if you suddenly have to go on a business trip or something, making you unable to stay at home and give your dog the pill exactly on the due date? Should you skip it this time? Or is it okay to give it earlier than the said date?

The simple answer is YES! It is okay to give heartworm meds to your dog early. Although it should be done on the 30th, it is okay to give it to him before that, for example, on the 25th or on the 21st.

However, you should keep in mind that the most dangerous thing is to delay the heartworm medicine or skip it. If that ever happens, heartworm larvae will mature into grown ones, which cannot be stopped by these preventive meds.

In other words, they will hurt your loved one or take their life!

What happens if you give heartworm medicine early?

This question is a little puzzling and can have two meanings. However, as a Veterinary student, I have the answer for both these perspectives. So read on, and you will find the answer you are seeking!

If you wonder whether you should start heartworm medicine at the early stage of heartworm infection, YES. The dog is a host for heartworms, and these worms live inside mature dogs and multiply.

They can harm the heart, lungs, and arteries and severely affect your dog’s health. So it is best to start the treatment as soon as possible and what will happen is it will save your dog’s life. Remember your dog should be tested before any treatment.

Then to the second perspective. If you have already started heartworm medication and wondering whether it is okay to give a dose earlier than the normal 30-day interval, the answer is again YES.

But there is an extremely important thing you should remember. Though there is no harm in giving it earlier, the cycle of meds should now be reset. The new date you have the meds now becomes the new monthly date for giving heartworm pills.

Heartworm pills only stay on your dog’s system for 24 to 48 hours. It will kill immature worms in that time. After that, it will be cleared off the system.

By the way, read this if your dog throws up medicine.

How long does Heartgard stay in the system?

Like any medicine with several brands out there, Heartgard is one of the brands for heartworm medicine. As these meds are given per month, many people assume it stays in the system for that whole period.

Wrong! Surprisingly, the period is much, much, much shorter than that! It is actually a day, or 4 days maximum.

The element that decides how long it stays in your dog’s body is its ingredients. For Heartgard, mainly, it is Ivermectin. Ivermectin can survive a half-life of 2 days in the dog.

In other words, 1/2 of the drug is discarded from the body in just 2 days. It means 4 days is the period it is active in each month.

With this revelation, many people ask how it can protect against heartworm for 30 days if it is active for just 4 days? For this, it is important to understand the method these meds work.

The heartworm medications work by eliminating heartworm the larvae that have infested your dog’s body in the last 30 days. That is why it is essential to give heartworm pills to your dog every 30 days to take care of the ones that can grow during that time.

Another question arises. What about the other ingredients? Like some other meds, Heartgard contains stuff against intestinal parasites and components against heartworms.

One of these ingredients is Pyrantel Pamoate. So how long does that stay in the body? Fortunately, it only lasts for around 24 hours, so there is no need to worry about those additional ingredients. But to make sure of it

 Furthermore, it is best to call it 3-5 days until you make sure all the worms are dead and gone for good.

Do dogs need heartworm medicine every month?

The direct answer to this question?Absolutely! As I mentioned earlier, monthly heartworm preventive drugs work by killing the worms when they are larvae. These larvae had been formed from a mosquito bite in the last month.

This heartworm medicine does not affect any further stage other than the larvae stage. After the larvae stage, drugs can’t kill them. This is why it is hazardous if you miss a monthly dose. By that time, the larvae can be mature enough not to be killed.

The research shows that for heartworm larvae to grow enough that meds don’t work on them, it takes about 40‒50. Because prevention is better than treatment, a period of easy-to-remember 30 days is recommended to give your dog heartworm pills.

Now when should you administer heartworm pills to your dog? Commonly, it is believed that tests should be done if you are planning to start medication for your 7-month or so dog if it hasn’t been on heartworm meds before.

Then they need to be tested for half a year, then a year each year.

Things to be aware of.

Like any other drug, heartworm drugs can also have side effects. So not just about heartworms, you should also be alert to its impact and any allergy possibilities.

It is important to keep in mind toxicity. It can be toxic to your dog if given too much, just like any other drug, because dogs are susceptible to most medication. Too much Ivermectin can be lethal in heartworm drugs because it can travel to brain tissue.

So if your dog is just a little puppy is good to be alert. In addition, several breeds are hypersensitive to ingredients in heartworm medication.

English sheepdog, Silken Windhound, German Shepherd, Collie, Shetland Sheepdog, Australian shepherd, and Longhaired whippet are some of those breeds.


So as I have mentioned above, now you know if it is okay to give your dog heartworm medicine early. The major point is that if you have given early, that day should be considered the new monthly date for giving the medication.

Though giving it early is okay, delaying is NOT OKAY! It will result in severe damage to your loved one, so never skip a heartworm prevention dose.

So I hope this article gave you the answers you are looking for. Hope it helps keep your beloved dog safe from heartworms so you can make their life span longer and your life with him happier!

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