Levothyroxine side effects in dogs
3,012 reports sent to the FDA between 1998 and 2026 involve Levothyroxine in dogs. The most reported problems were vomiting, loss of appetite, lethargy. 44% were marked serious, and where it was recorded, signs eased after stopping the medicine in 93% of cases.
3,012Reports
44%Marked serious
18%Only medicine involved
35%Recovered
8.4%Died or euthanised
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About this medicine
Levothyroxine treats an underactive thyroid.
Most reported side effects
Share = percentage of this medicine's reports that mention the problem. One report can list several problems.
Reports that it didn't work
Some reports are about the medicine not working (for example a dog still getting fleas or heartworm), not about a side effect.
How soon problems started
Time from the first dose to the first sign, where both dates were reported (1,803 reports).
How the animals did
Breeds named most often
Popular breeds appear more often because there are more of them.
- Labrador Retriever 300 reports
- Golden Retriever 227 reports
- Beagle 92 reports
- Boxer (german Boxer) 83 reports
- Chihuahua 53 reports
- German Pomeranian Spitz 52 reports
- German Shepherd Dog 47 reports
- Cocker American Spaniel 44 reports
- Yorkshire Terrier 43 reports
- Doberman Pinscher 42 reports