Weight loss after Methimazole in cats

247 reports to the FDA describe weight loss in cats given Methimazole. That is 14% of all reports for this medicine, compared with 4.6% across reports for all cat medicines, so it is reported unusually often with this medicine.

247Reports

57%Marked serious

12%Recovered

18%Died or euthanised

27 daysTypical onset

How soon it started

Same day

24 14%

1–2 days

8 4.5%

3–7 days

16 9.1%

1–4 weeks

50 28%

Over a month

78 44%

How the animals did

Recovered

29 12%

Recovered with lasting effects

1 0.4%

Still unwell when reported

60 24%

Died

20 8.1%

Euthanised

24 9.7%

Not known

113 46%

Problems reported at the same time

122 49%

76 31%

64 26%

48 19%

43 17%

40 16%

Didn't work as expected

40 16%

Dehydration

34 14%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

202

About this medicine

Methimazole treats an overactive thyroid in cats.

Questions owners ask

Can Methimazole cause weight loss in cats?: 247 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).

Weight loss with similar medicines

Weight loss after Velagliflozin (Senvelgo) 1,169 reports · 24% of its reports
Weight loss after Bexagliflozin (Bexacat) 1,090 reports · 27% of its reports
Weight loss after Insulin 196 reports · 5.2% of its reports

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