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My dog is lethargic after shots. Is this normal? When to call vet?

Updated on September 23rd, 2025

Pet's info: Dog | Mixed Breed | Male | neutered | 4 years and 8 months old | 17 lbs

My dog got a lepto, lime, and bordetella shot Thurs night. We come home today, he is lame and lethargic. How long will his reaction last? Should I rush him back to vet?

3 Answers

Most Helpful Answer

Answered By Dr. Heidi DVM, CVA, CCRT, CVTP, CVSMT, CVCH

Veterinarian, Certified Veterinary Acupuncturist, Certified Canine Rehabilitation Practitioner

Published on January 26th, 2018

I'm so sorry that Buddy isn't feeling well after his vaccinations. I would certainly recommend calling your vet to discuss his side effects and decide if he needs to be seen or not.
When we give a vaccination, the stimulation of the immune system can cause an inflammatory process that can result in some joint or muscle soreness. Some dogs will also be lethargic and can run a fever. These side effects will generally resolve within 1-2 days, but sometimes we will recommend giving medications to make the pets feel better in the meantime, so I would recommend discussing it with your vet. For the future, I generally will only give one vaccination at a time to dogs that have the potential to have vaccine reactions to minimize the potential for this to happen again.
Good luck! I hope that was helpful and that Buddy feels better soon. Thanks for using Petco Pet Education Center, formerly Petcoach.

2Pet Parents found this answer helpful

Related Answers from Veterinarians

Answered By Jennifer Ladd, DVM
Veterinarian
Published on August 4th, 2018
Vaccine reactions can vary widely, similar to humans. Mild symptoms include injection site tenderness, and transient lethargy (24 hours or so). Contact you veterinarian if lethargy persists, he stops eating, vomits, or has diarrhea. Emergency intervention would be respiratory distress, swollen face or a severe change in temperament due to fever/ more severe illness than listed above. These types of reactions are very rare. For my patients that show even mild vaccine reactions, I will reduce their vaccines to 1 booster per visit, and often will pre-medicate with Benadryl. I also prioritize my vaccines based on age of the animal, vaccine history and prevalence of disease in our region.
1Pet Parents found this answer helpful
Answered By Dr. Melanie, BVSc MS
Veterinarian
Published on January 23rd, 2017
It is normal to see some lethargy after receiving a vaccine, and it's good that he ate something. Benadryl will not help with lethargy, so I would not give him that at all. I also wouldn't take him into the emergency vet, just watch him tonight. The lethargy should pass in a day, so you can have him seen by a vet in the morning if he's still lethargic just to be safe. If he shows any of the following serious and less common side effects, I would have him seen by a vet immediately: persistent vomiting and diarrhea, itchy skin that seems to have bumps, swelling of the muzzle or around the face, severe coughing or difficulty breathing, or collapse.
1Pet Parents found this answer helpful

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Thanks for using Petco Pet Education Center, formerly Petcoach! Possible side effects after vaccines include pain at the injection site, lethargy, inappetence and general discomfort. This should subside within 1-2 days. If it does not improve or it worsens, have Boomer evaluated by a veterinarian for further assessment and treatment. Otherwise, Boomer will likely start feeling better shortly. Good luck and best wishes!

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