Forgot to Give Your Dog Heartworm Medicine? Process to Follow

Heartworm disease is a dangerous and fatal illness that can kill dogs. Therefore, preventative medication is key to solving this problem, yet what if I forgot to give my dog heartworm medicine? This article will guide dog owners step-by-step if they accidentally miss a dose of heartworm medicine for their dogs.

What if i forgot to give my dog heartworm medicine
What if i forgot to give my dog heartworm medicine

Understanding Heartworm Disease

Before getting into the main point, dog owners need to know about heartworm disease:

    • Definition and Cause: Heartworm disease is a serious and life-threatening sickness that can harm dogs worldwide. This parasite is caused by Dirofilaria immitis, which occupies residence in the heart and major blood vessels of the dog’s body.
    • Transmission Process: Heartworms spread via mosquitoes as vectors instead of jumping directly from dog to dog. When an infected mosquito bites a dog, it automatically transfers microscopic heartworm larvae into the dog’s bloodstream.
    • Life Cycle of Heartworms: Once these larvae travel through the bloodstream, they mature over several months and develop into adult worms eventually at the heart and major blood vessels. This maturation process can take up to 6 months, then adult ones can survive for several years inside the dog to cause significant health damage.
    • Geographical Spread: Heartworm disease is a global threat, but it happens popularly in warm and humid locations. Those places contain year-round mosquito activity that are prime breeding grounds for the parasites. Some factors like urbanization, travel habits, and mosquito control efforts also affect the spread of heartworm disease in many countries.
Image about life cycle of heartworms
Life Cycle of Heartworms

What to Do If You Miss a Dose

Here are steps on how to do if you have missed a dose of your dog’s heartworm medication:

Immediate Actions: If you forgot for less than 2 weeks, give it the missed dose of preventative right away and resume your regular monthly schedule. Most medications take at least 14 days to work, so your dog should still be protected.

Consulting a Veterinarian: If you have missed more than 2 weeks, contact your vet now to consult the best solution. Then, you may be recommended to adjust a preventative plan to prevent future gaps.

Testing for Heartworm Disease: As there is a delay in heartworm prevention, a simple blood test cannot accurately detect infection after missing a dose. Here are things you need to know about testing:

    • Timing of the test:  Before starting a heartworm test, your vet will suggest waiting at least 6 months after the missed dose. The duration is enough for any potential infection to develop and become detectable.
    • Type of test: There are two primary types of heartworm tests: an antigen and a microfilariae test. The vet will decide which test or combination of those is most appropriate for your dog’s situation.
Image about a dose of medication for your dog
Some measures to take action if you miss a dose of medication for your dog

The Importance of Prevention

Keeping your dog safe by using preventative medications on time is crucial. Here are the benefits:

Preventative Measures: There are various kinds of heartworm preventatives available:

    • Oral Medications: Chewable or flavored tablets are popular medications, working by eliminating microscopic heartworm larvae shortly after they enter the dog’s bloodstream. These tablets also effectively prevent baby worms from maturing into adult ones.
    • Topical Medications: These are applied topically between the dog’s shoulder blades once a month. They also kill heartworm larvae soon after infection and prevent them from developing similarly to oral medications.
    • Injectable Medications: They are long-lasting injections because they offer a duration of protection from 6 to 12 months depending on the specific medicine. Their function is to prevent the larvae from developing into adult worms.

Mechanism of Action: Most preventatives work depending on different brands and medications, but they commonly target the parasite’s energy production or disrupt its molting process. Eventually, they kill or inhibit the improvement of the larvae, preventing them from reaching maturity and causing harm to your dog.

Adherence to Prevention Schedule: Remember to give medications to your dog according to the recommended schedule. Missing one single dose can make your dog vulnerable to heartworm infection. Also, do not forget to discuss with your vet to determine the best preventative medicine for your dog based on their age, lifestyle, and other health conditions.

Image about preventative medications
Preventative medications are crucial

Prevention Strategies and Tips

Here are some strategies and tips for your preventative actions:

    • Year-round Heartworm Prevention: Regardless of geographic location or season, year-round heartworm prevention is still important for protecting your dog. This is because mosquitoes can live in various climates, a few bites from an infected mosquito can put your dog at risk of diseases.
    • Lifestyle Considerations: Regularly empty birdbaths, wading pools and ensure proper drainage to discard mosquito breeding grounds. Also limit outdoor time with your dog during dawn or dusk periods, or consider using protective gear like mosquito nets in high-risk circumstances.
Image about protect your dog
Some strategies and tips to protect your dog


What would happen if I forgot to give my dog her heartworm pill?

Don’t panic! Here are some following solutions if you have missed medications for:

    • Less than 2 weeks: Give your dogs the missed pill immediately and continue to follow your monthly schedule. Most pills offer at least 14 days.
    • More than 2 weeks: Consult with your veterinarian as soon as possible. They may ask to give the current dose and start a new preventative plan while adjusting the timing to prevent future gaps.

How long can a dog go without heartworm medicine?

This situation depends on the specific medication. Most preventatives offer a grace period of at least 14 days, but you should not rely on this. It is important to follow the recommended monthly schedule provided by your vet to ensure protection. Contact your vet now if you miss a dose!

How late can I give heartworm medicine?

If you are a few days late, it is still possible to give the missed dose to your dog and discuss with your veterinarian. Consistency is key! Do not wait too long between doses to avoid creating gaps in protection.


So what if I forgot to give my dog heartworm medicine? Do not worry! In case of less than 2 weeks, you need to give your dog medicine immediately. If the timing is more than 2 weeks, you should consult your vet for more advice. Hopefully, this article will help you address your concern and find the best preventative method for your dog.

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Lily Watson is an author specializing in veterinary care in Australia. With a profound passion for animal welfare and a solid foundation in veterinary science, Lily has dedicated herself to disseminating valuable knowledge and information for both pet owners and professionals in this field.