Diarrhea after Levothyroxine in dogs

The FDA has received 331 reports of diarrhea in dogs after Levothyroxine. That is 11% of all reports for this medicine, compared with 8.4% across reports for all dog medicines.

331Reports

55%Marked serious

40%Recovered

12%Died or euthanised

33 daysTypical onset

How soon it started

Same day

24 12%

1–2 days

22 11%

3–7 days

18 8.7%

1–4 weeks

39 19%

Over a month

104 50%

How the animals did

Recovered

122 37%

Recovered with lasting effects

11 3.3%

Still unwell when reported

86 26%

Died

12 3.6%

Euthanised

27 8.2%

Not known

73 22%

Problems reported at the same time

156 47%

118 36%

75 23%

54 16%

38 11%

37 11%

33 10.0%

33 10.0%

Age of the animals

Under 1 year

1–3 years

4–7 years

8–11 years

140

12+ years

120

About this medicine

Levothyroxine treats an underactive thyroid.

Questions owners ask

Can Levothyroxine cause diarrhea in dogs?: 331 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 33 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).

Diarrhea with similar medicines

Diarrhea after Trilostane (Vetoryl) 1,649 reports · 14% of its reports
Diarrhea after Insulin 393 reports · 5.3% of its reports
Diarrhea after Phenylpropanolamine (Proin) 383 reports · 9.3% of its reports
Diarrhea after Velagliflozin (Senvelgo) 20 reports · 28% of its reports

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