Is Monthly Heartworm Medicine Necessary?

You guys know that I try to keep unnecessary meds/shots under control. So when it was time to buy more heartworm medicine, I realized it’d been a couple of years since I’d researched the latest findings. I decided it was time to dig back in to find the current “facts”. Following is a map of heartworm incidence by state. Read on below to see my current protocol.


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While the above numbers are—by my book—pretty low, perhaps the rabid pushing for monthly dosing of HeartGuard year-round and other like medicines needs to be rethought. Especially since it takes 90 days for the microfilaria (baby heartworms) to grow to a larval stage; and even longer to grow into adult heartworms. If a dog is dosed with Ivermectin at any time during that 3-month larval period before adult heartworms are present, it will kill them.

Since I’m always looking for a happy medium, and I’d rather be safe than sorry, I’ve opted to dose every10 weeks for the duration of months with nightly temps over 55 degrees. I use Ivermectin Sheep Drench which I buy on Amazon. If you decide to go that route, read the first review for the correct dosing chart.

To meet my dogs’ weight requirements, here’s where we fall:

* 15 to 29 pounds: 0.1 cc
* 30 to 58 pounds: 0.2 cc

Here’s the side-by-side cost break-out comparison for 2 dogs:

Ivermectin                                                  Heartguard                              SAVINGS

$28  for 2 year supply       VS                $370 for Heartguard                    $342!

The most concise article I came across (that I then cross-checked for facts) was the The Billion Dollar Heartworm Scam.




4 thoughts on “Is Monthly Heartworm Medicine Necessary?”

  1. Dear Karen, I never worried about Heartworms until 1996. On a whim, I decided to have both our dogs tested. It turned out that our Black Lab Bucky had Heartworms and had to go through treatments. I never want to go through that again. Bucky had heart problems towards the end of his life. And I will always think it had something to do with those worms and the treatment he had to have because of it.

    We have three ponds on our place here in Missouri. So I will treat once a month year round. It is a personal decision that I feel confortable with. I see it as a personal decision based on personal circumstances. We now have five dogs and I try to be regular with the dosage. Most of the time, I hit at four weeks but sometimes it probably goes as long as six.

    1. Oh, Terri! I completely understand your choice! And I’m so sorry to hear that one of your dogs had to go through treatment. It is NO fun–for dog or owner. Which is why, even though there are many now who recommend completely going without, I am not in that camp. As I say, I would rather be safe than sorry.

      Thank goodness you thought to check on a whim. Which brings up the very important point that if someone is not going to treat year round, then they should test at least once a year.

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