Malaise after Levothyroxine in dogs

29 reports to the FDA describe malaise in dogs given Levothyroxine. That is 1.0% of all reports for this medicine, compared with 0.4% across reports for all dog medicines, so it is reported unusually often with this medicine.

29Reports

83%Marked serious

21%Recovered

34%Died or euthanised

151 daysTypical onset

How soon it started

Same day

0 0.0%

1–2 days

0 0.0%

3–7 days

1 6.7%

1–4 weeks

1 6.7%

Over a month

13 87%

How the animals did

Recovered

5 17%

Recovered with lasting effects

1 3.4%

Still unwell when reported

7 24%

Died

3 10%

Euthanised

7 24%

Not known

6 21%

Problems reported at the same time

14 48%

10 34%

8 28%

8 28%

8 28%

7 24%

5 17%

5 17%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

12+ years

About this medicine

Levothyroxine treats an underactive thyroid.

Questions owners ask

Can Levothyroxine cause malaise in dogs?: 29 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 151 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).

Malaise with similar medicines

Malaise after Trilostane (Vetoryl) 283 reports · 2.4% of its reports
Malaise after Insulin 73 reports · 1.0% of its reports
Malaise after Phenylpropanolamine (Proin) 24 reports · 0.6% of its reports

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