Ketosis after Methimazole in cats

The FDA has received 33 reports of ketosis in cats after Methimazole. That is 1.9% of all reports for this medicine, compared with 2.2% across reports for all cat medicines.

33Reports

30%Marked serious

0.0%Recovered

12%Died or euthanised

37 daysTypical onset

How soon it started

Same day

2 7.4%

1–2 days

2 7.4%

3–7 days

5 19%

1–4 weeks

3 11%

Over a month

15 56%

How the animals did

Still unwell when reported

12 36%

Euthanised

4 12%

Not known

17 52%

Problems reported at the same time

12 36%

9 27%

8 24%

7 21%

Didn't work as expected

6 18%

Diarrhea

6 18%

Death

4 12%

Lethargy

4 12%

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 ketosis in cats?: 33 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 37 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).

Ketosis with similar medicines

Ketosis after Velagliflozin (Senvelgo) 1,741 reports · 36% of its reports
Ketosis after Bexagliflozin (Bexacat) 1,483 reports · 37% of its reports
Ketosis after Insulin 85 reports · 2.3% of its reports

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