Swelling after Levothyroxine in dogs

The FDA has received 82 reports of swelling in dogs after Levothyroxine. That is 2.7% of all reports for this medicine, compared with 2.8% across reports for all dog medicines.

82Reports

61%Marked serious

26%Recovered

21%Died or euthanised

8 daysTypical onset

How soon it started

Same day

15 24%

1–2 days

8 13%

3–7 days

6 9.7%

1–4 weeks

11 18%

Over a month

22 35%

How the animals did

Recovered

20 24%

Recovered with lasting effects

1 1.2%

Still unwell when reported

29 35%

Died

5 6.1%

Euthanised

12 15%

Not known

15 18%

Problems reported at the same time

18 22%

18 22%

17 21%

15 18%

15 18%

15 18%

13 16%

12 15%

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 swelling in dogs?: 82 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 8 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).

Swelling with similar medicines

Swelling after Trilostane (Vetoryl) 149 reports · 1.2% of its reports
Swelling after Insulin 107 reports · 1.5% of its reports
Swelling after Phenylpropanolamine (Proin) 71 reports · 1.7% of its reports

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