Heartworm Testing And Why You Can't You Just Buy Heartworm Preventative

By Dino Dogan 

Every day is a good day to learn something new. Do you know why you can't just buy heartworm preventative on a whim and why your dog should be tested annually? Or would it be a surprise for you?

Sarge  7-17

I stopped by a local vet yesterday to pick up heartworm and flea/tick meds for my dog. I’ve never been to this particular vet so I encountered an issue that has never come up before.

I wasn’t allowed to buy the heartworm medicine!


I had to check the sign hung on the doors of America. Yup… sure enough…it still said United States of Capitalism. So I was confused.

Forgive me, I said to the lady at the reception desk. And why am I not allowed to buy heartworm medication for my dog?

She said that she’s not allowed to sell it.

If you’re getting frustrated with me not getting to the point, imagine how I felt. But allow me to be thorough.

Ok, but why? I said to her.

It could cause a pulmonary embolism. She said.
Editor's note: Pulmonary embolism is actually less likely to occur than a shock, caused by body's reaction to the dying larva in the bloodstream. Both, shock or pulmonary embolism, can be life threatening though.

Excuse me? Why wasn’t I aware of this? 

Do you mean to tell me that giving my dog heartworm meds can cause him to have a heart failure? Why are people selling this crap, to begin with?

If the dog ALREADY has heartworm, giving him the medication for it could cause a blood clot in his lungs. By the way son, pulmonary embolism is a lung failure, not heart failure. She added.

Ahhh…I see. So heartworm medication is a preventive measure ONLY. Ok. But why can’t I buy the medicine? My dog doesn’t have heartworm.

We can’t sell you the medicine because if the dog has heartworm the medicine could kill him and that would be our responsibility. She answered.

Now I’m confused again. How exactly are YOU responsible for MY dog? 

I didn’t say that but I thought it.

The vet was nearby and he was overhearing our conversation so he chimed in.

It’s impossible for owners to tell if their dog has heartworm. 

The onset is gradual and most of the time it looks like aging. The dog slows down, starts to go grey around the muzzle. Their coat loses its luster and their energy is depleted. Most owners welcome this kind of change because it means they don’t have to exercise the dog as much.

He also added. The heartworm test is mandated by both the American Heartworm Association AND the manufacturer of the heartworm medication.

Ahh…I get it. You are not responsible for my dog. I am responsible for my dog, but you are liable.

Exactly. He replied.

Thnx doc, I’ll just grab the flee/tick meds then.

That’ll be $49.95. The receptionist said.

A swipe of the credit card later I was on my way out the door slightly better off and more knowledgeable about my dog’s welfare than I was when I went in.

I hope you are too after reading this article.

Dogs should be tested at least once a year for heartworm and given appropriate preventive meds.

When was the last time you tested your dog?

Related articles:
Don't Let Heartworm Become A Heartbreak!
Hunter, Heartworm Positive


  1. Hi Y'all!

    My Humans actually knew this info, but didn't before adopting their last Chessie who, when vetted, had a serious case of heart worms.

    If you read the "In Memory" segment of my blog, you know everything turned out great and she lived to an ancient dog age.

    The related reading is excellent. They learn new stuff all the time about us pawed and furry critters. It's difficult to keep up without someone pointing us toward the pertinent articles.

    Y'all come by now,
    Hawk aka BrownDog

  2. I dont know why but I love seeing my articles on your blog :-)

  3. Hi Hawk, so glad that your buddy got well! I will check out the memory segment :-)

  4. Dino, that's neat :-) Btw did you notice the mosquito on the dog's face?

  5. Sadie and Rusty get annual checkups. The vet told me as long as I keep consistent with their heart-worm meds they will not have to get tested every year, in fact they haven't been tested since they were puppies. What's your take on the matter?

  6. Hi Kelley. In theory, yes. But there are enough variables in play that we do testing regularly in spite of religious year-round prevention.

    Better safe than sorry :-)

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  8. Hi sample. I am from Canada also. Yes, heartworm is in Canada also, at least at our region (Ontario).

    Used to be that preventative was give only for a portion of the year, but with the unstable weather (some very mild days during winter time) it is now recommended giving year-round.

    Although at one time confined to the southern United States, heartworm has now spread to nearly all locations where its vector, the mosquito, is found. Transmission of the parasite occurs in all of the United States (except Alaska) and the warmer regions of Canada.

    We are using Interceptor for our preventative.


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