Excited Cats is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no extra cost to you. Learn more.

Heartworm in Cats (Vet Reviewed Signs & Care FAQs)

Vet approved

	Dr. Lauren Demos (DVM) Photo

Reviewed & Fact-Checked By

Dr. Lauren Demos (DVM)


The information is current and up-to-date in accordance with the latest veterinarian research.

Learn more »

Heartworms in cats are similar to those in dogs. Similarly, they are difficult if not impossible to treat, and the best way to keep your cat healthy is to work with your vet to prevent them. Because heartworms can be so damaging to your cat’s health, getting immediate veterinary care can help alleviate the symptoms.

Your vet can also monitor them to see if they rid themselves of heartworms on their own. So, what signs of heartworms in cats should you be looking for? Keep reading to find out.

3 cat face divider

The 4 Possible Signs of Heartworm in Cats

1. Respiratory Problems

Heartworms don’t stay in the heart. They travel throughout the vascular system, and the first place they often end up is in the lungs, where they can restrict blood flow and cause inflammation.

You may notice intermittent coughing or signs that your cat has trouble breathing, like breathing with their mouth open. These symptoms are not unique to heartworms and should always be evaluated by your veterinarian for a proper diagnosis, but if heartworms are causing them, they must be addressed early.

When respiratory issues develop from heartworms this is called  Heartworm-Associated Respiratory Disease or HARD.1 While it can be challenging to treat heartworms in cats, your vet may be able to address the symptoms, making it easier for them to breathe.

thematic break

2. Lethargy

tired sick cat lying on bed
Image Credit: Natata, Shutterstock

If your cat seems tired and uninterested in their toys or other usual activities, it’s a sign that they should see the vet. Lethargy, like respiratory problems, is not a definite sign of heartworms in cats but can indicate something is wrong that should be diagnosed and treated. In combination with other symptoms on this list, it could mean that your cat has contracted heartworms, in which case their veterinarian is the best resource for advice and treatment. You know your cat best, so if they aren’t acting like themselves, trust your instincts.

thematic break

3. Weight Loss

Heartworms in cats can cause general unwellness that can lead to weight loss. Coughing associated with the disease can also precipitate vomiting.

You should take these concerns to your vet, who can determine the underlying cause and suggest appropriate treatment.

thematic break

4. Death

Death due to heartworms can come years after a diagnosis, while your cat has been living a somewhat normal life before succumbing to it. It can also come on suddenly, without knowing that your cat even had them. In this case, the only way to know that heartworms are to blame is for your vet to perform a post-mortem exam to determine the cause of an unexpected death.

Because the sudden death of a pet is shocking and heartbreaking, knowing what happened can help give closure and peace of mind, which is why some pet parents choose this option. It may also help prevent other pets in the home from getting sick if it is easily spread to others.

yarn ball divider

FAQs About Heartworms in Cats

How are Heartworms in Cats Diagnosed?

sick ginger cat

Many of the symptoms above can be signs of other cat diseases. Therefore, it’s crucial to pinpoint the exact cause so it can be treated in the best possible way and improve your cat’s quality of life. There are several ways to diagnose heartworms in cats.

If your vet suspects heartworms, they will most likely run some blood tests for heartworm antigens. X-rays and a cardiac ultrasound may also show the presence of heartworms.

Can Heartworms be Treated?

The medications used for dogs cannot be used for cats, so there’s no effective treatment to cure heartworms in cats. Some cats may rid themselves of heartworms on their own after a few years, so your vet will recommend testing every 6 to 12 months or as symptoms require it. While there isn’t a way to permanently cure heartworms in cats, your vet can help treat the many signs to make your cat more comfortable.

Can They be Prevented?

Even indoor cats are susceptible to them, but if they are prevalent in your area or your cat is frequently outside, you must work with your vet to prevent heartworms. A monthly treatment could be a topical medication or pill, but it should be given on a strict schedule to ensure your pet is protected. You’ll need a prescription from your vet to purchase heartworm prevention medications, or you can buy them directly from their clinic in most cases.

cat paw divider


Heartworms in cats can be serious, and if you see your cat behaving strangely or showing signs of distress, get them to a vet immediately. If they determine that heartworms are the cause, you can work closely with them to ensure your cat remains as healthy as possible with the hope that they may clear the worms on their own. If not, remain vigilant in watching for signs of their condition worsening so you can see their vet.

See also:

thematic break

Featured Image Credit: Kachalkina Veronika, Shutterstock