Excessive thirst after Levothyroxine in dogs

179 reports to the FDA describe excessive thirst in dogs given Levothyroxine. That is 5.9% of all reports for this medicine, compared with 1.4% across reports for all dog medicines, so it is reported unusually often with this medicine.

179Reports

64%Marked serious

18%Recovered

12%Died or euthanised

25 daysTypical onset

How soon it started

Same day

17 15%

1–2 days

11 9.6%

3–7 days

14 12%

1–4 weeks

21 18%

Over a month

52 45%

How the animals did

Recovered

26 15%

Recovered with lasting effects

7 3.9%

Still unwell when reported

66 37%

Died

6 3.4%

Euthanised

15 8.4%

Not known

59 33%

Problems reported at the same time

120 67%

43 24%

43 24%

41 23%

39 22%

36 20%

27 15%

Didn't work as expected

23 13%

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 excessive thirst in dogs?: 179 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 25 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).

Excessive thirst with similar medicines

Excessive thirst after Trilostane (Vetoryl) 873 reports · 7.3% of its reports
Excessive thirst after Insulin 526 reports · 7.1% of its reports
Excessive thirst after Phenylpropanolamine (Proin) 180 reports · 4.3% of its reports

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