Anxiety after Levothyroxine in dogs

57 reports to the FDA describe anxiety in dogs given Levothyroxine. That is 1.9% of all reports for this medicine, compared with 0.5% across reports for all dog medicines, so it is reported unusually often with this medicine.

57Reports

58%Marked serious

46%Recovered

11%Died or euthanised

42 daysTypical onset

How soon it started

Same day

4 11%

1–2 days

1 2.8%

3–7 days

5 14%

1–4 weeks

7 19%

Over a month

19 53%

How the animals did

Recovered

25 44%

Recovered with lasting effects

1 1.8%

Still unwell when reported

12 21%

Died

1 1.8%

Euthanised

5 8.8%

Not known

13 23%

Problems reported at the same time

Breathing problems

15 26%

Restlessness or agitation

15 26%

Overdose

14 25%

Didn't work as expected

11 19%

11 19%

10 18%

9 16%

9 16%

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 anxiety in dogs?: 57 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 42 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).

Anxiety with similar medicines

Anxiety after Trilostane (Vetoryl) 204 reports · 1.7% of its reports
Anxiety after Insulin 43 reports · 0.6% of its reports
Anxiety after Phenylpropanolamine (Proin) 101 reports · 2.4% of its reports

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