Why Is My Cat So Tired After Vaccines?

Dr. Joe Alcorn, M.S., D.V.M.

Dr. Joe Alcorn is founder of Care Animal Hospital in Temecula, California. He has a Bachelor of Science in Biology and Doctor of Veterinary Medicine from Colorado State University. He is a member of the American Veterinary Medical Association and his advice has been featured in large publications like Bustle and Martha Steward.

Home » Blog » Why Is My Cat So Tired After Vaccines?

Vaccines help maintain your cat’s health and well-being. However, you may notice some cats feeling less energetic after getting their shots, prompting them to sleep for the rest of the day. We’re explaining why your cat feels so tired after vaccinations and how to make your pet feel better.

Why Is My Cat So Tired After Vaccines?

Your cat feels so tired after vaccines because the shots stimulate the immune system to release antibodies to fight off potential diseases, triggering a mild fever. An upset stomach, soreness, and cold-like symptoms can make cats feel quite exhausted. These are normal reactions to immunization, lasting within a day or two.

Feeling sleepy after getting their shots is typical for cats, especially for kittens getting their first doses. You must understand how vaccines work, so you’ll know why your pet needs to rest afterward.

Yellow tabby cat yawning while sitting on a bed

Reasons Why Vaccines Make Cats Feel Tired

A vaccine is an organism’s modified form, consisting of antigens for a disease. When your cat gets injected, the immune system responds by releasing antibodies for a particular infectious organism.

Pet vaccinations stimulate an animal’s immune response to help cells circulate in the body. Thus, when your cat is exposed to a bacteria or virus, your pet’s immune system is ready to fight it. The process can consume more energy than usual, making cats tired and sleepy afterward.

Side Effects of Cat Vaccine

Most of the side effects of cat immunization are mild and shouldn’t last long. However, you must still observe these potential side effects because these can make your cat tired after vaccination.


Your cat’s body will consume energy once the immune system releases antibodies. Like humans, cats may feel tired and a little sleepy after getting a shot.

Some veterinarians also provide a mild sedative to anxious cats. The sedative adds drowsiness in the process.

Mild Stomach Upset

Your pet may also experience a decreased appetite within 24 or 48 hours after vaccination. In effect, your pet may have a mild stomach upset, also causing it to feel lethargic.

Cats tend to withdraw when they have an upset stomach. About 40% of adult cats can sleep up to 18 hours a day, more when they’re not feeling well. Although they look like they are in a deep sleep, cats remain pretty alert to their surroundings.

Assistant holding onto a black and gray cat while a veterinarian is holding a syringe

Localized Swelling

Soreness in the injection site is among immunization’s most common side effects. Your cat may feel extra protective of its body due to soreness. Your cat may not feel like exercising or playing outdoors.

When there’s a sore body part, your cat’s body responds to slight pain, making it feel tired. Consult our vets if the lump grows, shows signs of infection, or doesn’t disappear within a week.

Cold-Like Symptoms

Cats feel so tired after vaccinations because they may experience cold-like symptoms such as runny nose, sneezing, and coughing. A slight fever may last within a day or two.

A People’s Dispensary for Sick Animals report shows that only 61% of cat owners secured core vaccinations for their pets. One reason for such reluctance is fear of side effects, including cold-related ones.


Severe anaphylaxis reactions can show within 48 hours after getting the shot. This is the most severe allergic reaction your cat can get from immunization.

In rare cases, cats may have an allergic reaction to modern vaccines, leading to extreme weakness, hives, nausea, and collapse. Contact my clinic immediately for emergency care and services if you notice difficulty breathing, vomiting, excessive drooling, and diarrhea a few hours after the vaccination.

Ways to Make Your Cat Feel Better After Getting Shots

Cats feel tired after getting vaccinated because its body does a lot of work releasing antibodies to fight off bacteria. This process can make them drowsy and experience soreness, cold-like symptoms, and even an upset stomach.

These are ways you can make your cat feel better after immunization.

White and gray cat sleeping on its back with its paws up
  • Provide a quiet place to rest: Your cat will most likely want to sleep after your vaccine appointment. Let your pet rest comfortably, away from noises or commotion.
  • Give plenty of fluids: Be sure your pet has access to fresh, clean water to avoid dehydration.
  • Monitor appetite: While your cat may lose its appetite, you must still encourage your pet to eat at the right time.
  • Avoid playing: Your pet may feel soreness in the injection site for a few hours. It would be much better to keep your cat away from other pets and avoid playing for a while to prevent applying unnecessary force.
  • Give some alone time: Don’t force your pet to pay attention to you if it wants to be left alone.
  • Check temperature: Cats have an average body temperature of 100 to 102.5 degrees Fahrenheit. If it goes above 103 degrees Fahrenheit, this temperature can be too hot for your cat to handle.

Related Questions

How Can I Prevent My Cat From Having an Allergic Reaction to Vaccines?

To prevent your cat from allergic reactions to vaccines, our vets can administer the shots for your cat at different times or even weeks apart instead of giving multiple vaccines at once. Depending on your pet’s health, we also recommend skipping certain vaccines for the time being.

How Long Do Cat Vaccine Side Effects Last?

Minor side effects of cat vaccines should last around 24 to 48 hours, while major ones may go beyond two days. If the effects make your cat extremely uncomfortable, it would be wise to bring your pet to my clinic for examinations.

Should I Vaccinate My Cat Despite Side Effects?

Yes, it’s essential you should vaccinate your cat despite side effects and even if it feels tired afterward. As a pet owner, you are responsible for your pet’s well-being, and securing vaccines can protect your feline friend’s long-term health.


Your cat feels tired after getting vaccines because it takes energy for the immune system to release antibodies that will fight off bacteria in the future. Mild symptoms, including tiredness and sleepiness, are entirely normal. After that, your pet will return to its old, energetic self in no time.