Year-Long Heartworm Shots for Dogs

As every dog owner knows, heartworm prevention is crucial for the health and well-being of our furry friends. Over the past few years, there’s been buzz surrounding an annual heartworm injection. But what is it? And is it the right choice for your dog?

What is the Year-Long Heartworm Shot?

The year-long heartworm shot, often referred to by its brand name, ProHeart 12, is an injectable medication that offers 12 months of heartworm disease protection. It contains the active ingredient moxidectin, which gradually releases into the dog’s system to offer prolonged protection against heartworm disease.

Benefits of the Yearly Injection

  1. Convenience: No need to remember monthly tablets or chews.
  2. Consistency: Eliminates the risk of missed doses, ensuring consistent protection.
  3. Safety: Proven effective with minimal side effects when administered correctly.

Potential Side Effects

While the ProHeart 12 injection is generally considered safe, as with any medication, there are potential side effects to be aware of:

  • Lethargy or tiredness
  • Decreased appetite
  • Vomiting
  • Swelling or itching at the injection site

Always consult with your veterinarian if you notice any unusual behaviors or symptoms in your dog after the injection.


While the upfront cost of the ProHeart 12 injection can be more than monthly preventatives, many owners find it cost-effective in the long run. By administering one injection per year, owners can save on the cumulative expense and potential price hikes of monthly treatments.

Monthly Tablets vs. Yearly Injection: Which is Better?

The choice between monthly and yearly heartworm prevention often boils down to owner preference and the specific needs of the dog:

  • Monthly Tablets: These can be combined with other parasite preventatives and may be ideal for dogs that require comprehensive protection.
  • Yearly Injection: Best for those who prefer a once-a-year solution and are solely focused on heartworm prevention.

Expert Opinions

Veterinarians emphasize the importance of consistent heartworm prevention. While some prefer the reliability of the annual shot, others champion the broad-spectrum protection offered by certain monthly treatments. The key is to discuss your dog’s lifestyle, health needs, and your preferences with your veterinarian to find the best fit.

Conclusion: The Heart of the Matter

The introduction of the year-long heartworm shot has provided dog owners with an effective, convenient option for protecting their pets. Whether you choose the annual injection or monthly tablets, the most important thing is ensuring consistent protection against heartworm disease.


1. How does the year-long heartworm shot work?

The ProHeart 12 injection releases the active ingredient, moxidectin, steadily into the dog’s system over the year. This substance targets the larvae of the heartworm parasite, preventing them from maturing and causing harm.

2. Are there specific breeds or ages for which the shot isn’t recommended?

While the injection is safe for most breeds and ages, it’s primarily recommended for dogs over one year old. For puppies or breeds with specific health concerns, always consult your veterinarian for tailored advice.

3. Can I switch from monthly preventatives to the yearly shot?

Yes, you can transition from monthly treatments to the annual injection. However, it’s vital to ensure there’s no gap in protection. Before the switch, your dog will undergo a heartworm test to ensure they’re free from infection.

4. What if my dog has a history of heartworm infection?

Dogs previously treated for heartworm can benefit from the annual injection, but they should undergo periodic testing. This ensures they remain heartworm-free, and the prevention method remains effective.

5. Can the year-long shot be combined with other parasite preventatives?

Yes, the yearly shot can be used alongside other parasite preventatives for ticks, fleas, and intestinal worms. Discuss with your veterinarian to create a holistic prevention plan tailored to your dog’s needs.

6. What should I do if I suspect an adverse reaction to the shot?

If your dog exhibits unusual symptoms or behaviors following the injection, contact your veterinarian immediately. While side effects are rare, timely intervention ensures your dog’s safety.

7. Are there geographical regions where the yearly shot is more beneficial?

Heartworm is more prevalent in humid and warm regions, such as the American South. In these areas, consistent year-round prevention is crucial. The yearly shot ensures continuous protection, eliminating any lapses that might occur with missed monthly doses.

8. How often should my dog be tested for heartworm if on the annual injection?

Regular testing is paramount. Even if your dog is on the year-long shot, annual heartworm testing is recommended. This ensures the preventative remains effective and your dog stays heartworm-free.

9. Does the year-long shot also protect against other parasites?

While the ProHeart 12 injection offers protection against heartworms, it doesn’t safeguard against ticks, fleas, or most intestinal parasites. It’s essential to combine it with other preventive measures for comprehensive protection.

10. What’s the general veterinarian consensus on the year-long shot?

Many veterinarians view the year-long shot as a reliable and effective preventative measure, especially for dog owners who may forget monthly doses. However, the choice between monthly treatments and the yearly shot often hinges on individual circumstances and veterinarian recommendations.

11. How does ProHeart 12 compare to ProHeart 6 in terms of efficacy?

Both ProHeart 12 and ProHeart 6 use the same active ingredient, moxidectin. The primary difference lies in their duration of protection – 12 months versus 6 months, respectively. Their efficacy rates are comparably high when administered correctly.

12. How does the cost of the yearly shot compare to monthly preventatives?

While the upfront cost of the yearly shot might seem higher, it can be cost-effective in the long run. The annual injection might offset the cumulative cost of monthly treatments, especially when considering potential missed doses and the risk of heartworm infection.

13. Can pregnant or nursing dogs receive the yearly heartworm shot?

It’s essential to consult with a veterinarian regarding pregnant or nursing dogs. Current recommendations advise caution. The shot’s safety for pregnant or lactating dogs hasn’t been adequately established.

14. If I move to a region with lower heartworm prevalence, should I continue with the yearly shot?

Heartworm transmission risk varies by region. If you relocate, it’s vital to assess local risks with a regional vet. However, heartworm cases have been reported in all US states, so consistent prevention remains crucial.

15. How does the yearly shot fit into a holistic health plan for my dog?

The year-long heartworm shot can be an integral part of a broader health strategy for your dog. Coupled with regular check-ups, vaccinations, and other preventive measures, it ensures your pet remains protected against a spectrum of potential health threats.

16. What happens if my dog misses their yearly reinjection date?

If the reinjection date is missed, there’s a risk of decreased protection. Schedule an appointment with your vet as soon as possible. They may require a heartworm test before administering the next injection.

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