Dehydration after Levothyroxine in dogs

32 reports to the FDA describe dehydration in dogs given Levothyroxine. That is 1.1% of all reports for this medicine, compared with 0.7% across reports for all dog medicines, so it is reported unusually often with this medicine.

32Reports

88%Marked serious

22%Recovered

41%Died or euthanised

75 daysTypical onset

How soon it started

Same day

3 15%

1–2 days

1 5.0%

3–7 days

1 5.0%

1–4 weeks

4 20%

Over a month

11 55%

How the animals did

Recovered

5 16%

Recovered with lasting effects

2 6.3%

Still unwell when reported

9 28%

Died

3 9.4%

Euthanised

10 31%

Not known

3 9.4%

Problems reported at the same time

24 75%

19 59%

17 53%

16 50%

13 41%

13 41%

12 38%

11 34%

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 dehydration in dogs?: 32 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 75 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).

Dehydration with similar medicines

Dehydration after Trilostane (Vetoryl) 195 reports · 1.6% of its reports
Dehydration after Insulin 106 reports · 1.4% of its reports
Dehydration after Phenylpropanolamine (Proin) 54 reports · 1.3% of its reports

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