Fever after Methimazole in cats

42 reports to the FDA describe fever in cats given Methimazole. That is 2.4% of all reports for this medicine, compared with 3.2% across reports for all cat medicines.

42Reports

90%Marked serious

21%Recovered

31%Died or euthanised

22 daysTypical onset

How soon it started

Same day

3 9.1%

1–2 days

2 6.1%

3–7 days

1 3.0%

1–4 weeks

21 64%

Over a month

6 18%

How the animals did

Recovered

8 19%

Recovered with lasting effects

1 2.4%

Still unwell when reported

13 31%

Died

7 17%

Euthanised

6 14%

Not known

7 17%

Problems reported at the same time

30 71%

21 50%

13 31%

12 29%

12 29%

11 26%

11 26%

11 26%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Methimazole treats an overactive thyroid in cats.

Questions owners ask

Can Methimazole cause fever in cats?: 42 reports link the two, but a report alone does not prove the medicine was the cause: other illnesses, other medicines or coincidence can be involved. Your vet can judge it for your animal.
How soon after a dose was it reported?: In half of the reports with dates, it started within 22 days of the first dose.
What should I do?: Don't give another dose until you've spoken to your vet, and keep the packaging so you can tell them the product and dose. Your vet can also report it to the FDA (or you can, through the manufacturer or FDA form 1932a).

Fever with similar medicines

Fever after Velagliflozin (Senvelgo) 37 reports · 0.8% of its reports
Fever after Bexagliflozin (Bexacat) 40 reports · 1.0% of its reports
Fever after Insulin 34 reports · 0.9% of its reports

All reported side effects of Methimazole in cats · Medicines most reported with fever