Blood problems after Methimazole in cats

The FDA has received 99 reports of blood problems in cats after Methimazole. That is 5.6% of all reports for this medicine, compared with 1.9% across reports for all cat medicines, so it is reported unusually often with this medicine.

99Reports

75%Marked serious

7.1%Recovered

30%Died or euthanised

27 daysTypical onset

How soon it started

Same day

6 8.6%

1–2 days

3 4.3%

3–7 days

0 0.0%

1–4 weeks

30 43%

Over a month

31 44%

How the animals did

Recovered

7 7.1%

Still unwell when reported

28 28%

Died

16 16%

Euthanised

14 14%

Not known

34 34%

Problems reported at the same time

47 47%

35 35%

31 31%

28 28%

26 26%

24 24%

21 21%

17 17%

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 blood problems in cats?: 99 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 27 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).

Blood problems with similar medicines

Blood problems after Velagliflozin (Senvelgo) 44 reports · 0.9% of its reports
Blood problems after Bexagliflozin (Bexacat) 68 reports · 1.7% of its reports
Blood problems after Insulin 56 reports · 1.5% of its reports

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