Can Puppy Shots Cause Them to Be Sleepy or Lethargic?

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If you have a puppy, you know that they tend to play hard, sleep hard, and then sleep some more. However, if your dog is extra sleepy or lethargic after receiving their puppy shots, this could indicate a vaccine reaction.

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Are vaccine reactions in dogs normal?

Yes, some minor vaccine reactions in dogs is normal.‌ While most lethargy following puppy vaccines is normal and will resolve within a day or so, it is important to know the difference between mild grogginess and what might be a more severe vaccine reaction that requires immediate veterinary attention.


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If you are nervous about getting your puppy vaccinated, it might help to know that severe reactions don't happen often, and vaccines can help ensure your dog's long-term health. Knowing what to look out for can also make you feel more confident and prepared.

Side effects after puppy shots

In addition to lethargy, your puppy might display some other mild symptoms. The most common side effects are temporary loss of appetite, soreness or a small amount of swelling around the injection site, or a mild fever. Your puppy may be a little under the weather for a couple of days, but they should be back to their normal playful self after that. Even with modest side effects, it is always best to call your veterinary clinic if you have any concerns following your dog's vaccinations.


Most severe allergic reactions will occur within minutes to hours after the injection, but some can take up to 48 hours to appear. Watch for extreme lethargy (meaning very low energy and inactivity) as well as facial swelling, hives, vomiting, diarrhea, difficulty breathing, or collapse. These issues indicate a more serious vaccine reaction that needs immediate medical attention. In rare cases, adverse reactions can be life-threatening, so take your dog for emergency veterinary care right away if they experience any of these reactions.


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Preparing for puppy shots

There are a few things pet parents can do to make the vaccine appointment go as smoothly as possible.


Reading up on core vaccines, vaccine side effects, and why your puppy needs vaccines can help you feel prepared. Core vaccines are essential shots that all dogs should have. Not only is the rabies vaccine a core immunization but it is also required by law for dogs in most states. Additional core vaccines include canine distemper virus, canine parvovirus, canine adenovirus-2, and parainfluenza virus (often given as a combination shot known as DA2PP).



Non-core vaccines are just as essential since they protect against serious illnesses. Your veterinarian will recommend certain vaccines based on your dog's lifestyle, geographic location, and exposure risk. These can include Lyme disease, Bordetella bronchiseptica, canine influenza, and leptospirosis. Because of increasing prevalence, leptospirosis should be considered for all dogs. Specific vaccinations, like leptospirosis, will be started a bit later than the initial core vaccines.


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Planning your dog's vaccines

Before their vaccine appointment, try to get a sense of how much time your puppy spends sleeping each day so you can quickly identify if your puppy is lethargic after their shots. It is also a good idea to schedule puppy vaccinations for days when you can be home with them. You or someone you trust should stay with your dog for the first several hours after vaccination.


If your dog has had vaccines before and experienced a reaction, make sure to tell your veterinarian about this prior to all future vaccinations. Your veterinarian might pretreat your dog with an allergy medication before administering the vaccine.

The bottom line

Some puppies experience lethargy as a side effect of vaccines but don't let the fear of a reaction stop you from getting your dog their shots. Mild sleepiness following vaccines is normal and usually does not require medical attention. Extreme lethargy is rare, but if this does happen to your puppy, you'll know to head to your nearest emergency animal hospital right away. Keep in mind that the pet health benefits of vaccines far outweigh their risks.



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