Hyperkalaemia after Levothyroxine in dogs

The FDA has received 56 reports of hyperkalaemia in dogs after Levothyroxine. That is 1.9% of all reports for this medicine, compared with 0.3% across reports for all dog medicines, so it is reported unusually often with this medicine.

56Reports

54%Marked serious

7.1%Recovered

16%Died or euthanised

127 daysTypical onset

How soon it started

Same day

0 0.0%

1–2 days

0 0.0%

3–7 days

1 3.2%

1–4 weeks

2 6.5%

Over a month

28 90%

How the animals did

Recovered

2 3.6%

Recovered with lasting effects

2 3.6%

Still unwell when reported

14 25%

Died

2 3.6%

Euthanised

7 13%

Not known

29 52%

Problems reported at the same time

Liver problems

24 43%

Kidney problems

23 41%

Low sodium-potassium ratio (na:k ratio)

22 39%

16 29%

15 27%

13 23%

12 21%

11 20%

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 hyperkalaemia in dogs?: 56 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 127 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).

Hyperkalaemia with similar medicines

Hyperkalaemia after Trilostane (Vetoryl) 1,751 reports · 15% of its reports
Hyperkalaemia after Insulin 142 reports · 1.9% of its reports
Hyperkalaemia after Phenylpropanolamine (Proin) 23 reports · 0.6% of its reports

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