Excessive urination after Levothyroxine in dogs

The FDA has received 132 reports of excessive urination in dogs after Levothyroxine. That is 4.4% of all reports for this medicine, compared with 1.0% across reports for all dog medicines, so it is reported unusually often with this medicine.

132Reports

61%Marked serious

17%Recovered

13%Died or euthanised

22 daysTypical onset

How soon it started

Same day

14 16%

1–2 days

6 7.1%

3–7 days

11 13%

1–4 weeks

18 21%

Over a month

36 42%

How the animals did

Recovered

17 13%

Recovered with lasting effects

6 4.5%

Still unwell when reported

56 42%

Died

3 2.3%

Euthanised

14 11%

Not known

36 27%

Problems reported at the same time

120 91%

36 27%

31 23%

28 21%

27 20%

23 17%

20 15%

19 14%

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 urination in dogs?: 132 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 22 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 urination with similar medicines

Excessive urination after Trilostane (Vetoryl) 772 reports · 6.5% of its reports
Excessive urination after Insulin 473 reports · 6.4% of its reports
Excessive urination after Phenylpropanolamine (Proin) 81 reports · 2.0% of its reports

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