Peer-reviewed veterinary case report
Cat treated for hyperthyroidism with methimazole developed anemia
By Mastrangelo, Cristian·Published in The Canadian veterinary journal = La revue veterinaire canadienne·2025·Ontario Veterinary College, Canada·View original on PubMed →
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Original publication title: Adverse side effects, including agranulocytosis and anemia, from methimazole treatment of a hyperthyroid cat.
- Species:
- cat
Plain-English summary
A 13-year-old spayed female domestic shorthair cat was brought to the vet because she was very tired and not eating. She had been treated for hyperthyroidism with a medication called methimazole for about 40 days. Blood tests showed she had severe anemia and low white blood cell counts, which can be serious. After stopping the methimazole, her blood cell counts returned to normal, and she started to feel better. This case highlights the importance of regular check-ups for cats on methimazole to monitor for side effects.
People also search for: cat lethargy and not eating · hyperthyroid cat treatment side effects · methimazole anemia in cats
Abstract
A 13-year-old spayed female domestic shorthair cat was brought to a veterinary clinic because of lethargy and anorexia. The cat had a history of hyperthyroidism and had been treated with methimazole for 40 d before the appointment. Hematologic examination revealed a severe non-regenerative anemia and leukopenia characterized by severe neutropenia along with low basophil and eosinophil numbers. Discontinuation of methimazole resulted in the complete return to normal values of the white blood cell numbers and a marked increase in red blood cell numbers. This case demonstrated the need for follow-up veterinary examinations after prescription of methimazole treatment.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/39898169/