Liver problems after Levothyroxine in dogs

319 reports to the FDA describe liver problems in dogs given Levothyroxine. That is 11% of all reports for this medicine, compared with 4.6% across reports for all dog medicines, so it is reported unusually often with this medicine.

319Reports

68%Marked serious

14%Recovered

22%Died or euthanised

47 daysTypical onset

How soon it started

Same day

18 9.7%

1–2 days

11 5.9%

3–7 days

12 6.5%

1–4 weeks

37 20%

Over a month

108 58%

How the animals did

Recovered

27 8.5%

Recovered with lasting effects

19 6.0%

Still unwell when reported

117 37%

Died

19 6.0%

Euthanised

50 16%

Not known

87 27%

Problems reported at the same time

112 35%

97 30%

97 30%

82 26%

68 21%

64 20%

54 17%

Abnormal ultrasound finding

51 16%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

143

12+ years

128

About this medicine

Levothyroxine treats an underactive thyroid.

Questions owners ask

Can Levothyroxine cause liver problems in dogs?: 319 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 47 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).

Liver problems with similar medicines

Liver problems after Trilostane (Vetoryl) 2,663 reports · 22% of its reports
Liver problems after Insulin 417 reports · 5.7% of its reports
Liver problems after Phenylpropanolamine (Proin) 289 reports · 7.0% of its reports

All reported side effects of Levothyroxine in dogs · Medicines most reported with liver problems