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Why is my cat tired and not eating after Cetirizine for allergies?

Updated On September 23rd, 2025

Pet's info: Cat | Turkish Angora | Male | neutered | 7 years and 6 months old | 13.5 lbs

Is lethargy and loss of appetite common for cats prescribed Cetirizine (5 mg syrup) after being diagnosed with allergies? My cat was fine when I gave the dose yesterday afternoon, but this morning he wasn't interested in his food. He drank some water, but he seems tired. Is this normal and can I continue giving him the medicine? He was prescribed to take 5mg Cetirizine once a day for 7 days. Please advise.

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1 Answer

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Answered By Dr. Leigh, DVM

Veterinarian

Published on October 11th, 2021

Although uncommon, cetirizine can cause sedation, lethargy, and lack of appetition animals. Please call your vet and discuss the clinical signs that he is experiencing. Your vet may want to switch medications or might want to see your cat to make sure there isn't something else causing the problem.

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