My dog is lethargic, won't eat after heartworm shot. What's wrong?

I'm sorry Aria has heartworms! The fact that she is lethargic and has a decrease in appetite is concerning, and this can be due to the sudden death of a large number of worms from the treatment. When a dog becomes lethargic as well as has a significant decrease in appetite, it's recommended to have them seen by a vet right away. I would take her into an ER vet clinic; if there isn't one in your area, there will be a vet on call for emergencies. The information to reach that vet is found on a clinic's answering machine or website. She needs to be checked out by a vet to make sure everything is ok. I hope this helps and that she feels better soon!

This treatment could cause lethargy, it's quite common and this is one of the reason restriction is a must. if she becomes too lethargic you might need to take her to the ER, especially if you notice abnormal breathing.

Thanks for using Petco Pet Education Center, formerly Petcoach! Yes, sometimes as the worms are dying off that can result in respiratory issues as they dislodge. Paleness and cold extremities can sometimes be seen in patients that have abnormal oxygen delivery which can happen in these cases. Usually the first 2 weeks are critical when treating for heartworms. I recommend that you him evaluated by your veterinarian for further assessment. It would be good to check if he is having any issues with oxygen delivery. Good luck!

Hi and thank you for using Petco Pet Education Center, formerly Petcoach. He may be having a vaccine reaction. Sometimes it can be painful at the injection site and dogs can be sore. I would recommend calling your veterinarian tonight and letting them know that Wolfie is not feeling great. They may prescribed him some anti-inflammatory medication, fluids or anti-nausea medication to help him feel a little better. Good luck!

Hello and thanks for using Petco Pet Education Center, formerly Petcoach! I'm sorry to hear that Lyla is not herself! I think it would be a good idea to take her to your veterinarian. There are many things that could be causing these signs in a younger dog (gastrointestinal disease or parasites, infection, heart worm disease) so I think it's very important you have Lyla examined. Good luck and I hope Lyla is feeling better soon!

The injection can be very painful. This could be why she is shivering. If it persists, contact your veterinarian and ask about pain management. If she becomes extremely lethargic or extremely painful, have her rechecked by your veterinarian or at the nearest veterinary ER.

Any change in breathing warrants a trip to the vet for a recheck. While it’s possible that there’s nothing wrong, you could also be noticing the beginning of a complication of heartworm treatment. Pulmonary thromboembolism can occur when dying worms become lodged in the small blood vessels of the lungs. Your vet might want to take a chest x-ray.