My dog ate thyroid medication (levothyroxine) — what should I do?
GREEN — Usually watch at home
What to do now
- Usually not dangerous in small amounts. Watch for the symptoms below for the next 24 hours.
- Call your vet if symptoms appear, the amount was large, or your dog is very small, old, or ill.
- Remove any remaining material and keep packaging/labels — the vet will want product names and amounts.
- Do not induce vomiting unless a vet or poison-control expert tells you to.
- Note the time it was eaten, roughly how much, and your dog's weight.
Why it's a problem
Dogs tolerate high doses of thyroid hormone; acute overdose rarely causes more than mild signs.
Symptoms to watch for
Restlessness, panting, vomiting (large doses).
When: Hours
⚠️ Very large ingestions or dogs with heart disease -> call your vet.
Frequently asked questions
Is thyroid medication (levothyroxine) dangerous for dogs?
Usually not seriously. Dogs tolerate high doses of thyroid hormone; acute overdose rarely causes more than mild signs. Monitor and call your vet if symptoms appear.
What are the symptoms if my dog ate thyroid medication (levothyroxine)?
Restlessness, panting, vomiting (large doses).
How soon do symptoms appear after a dog eats thyroid medication (levothyroxine)?
Hours
Is there anything else to know about thyroid medication (levothyroxine)?
Very large ingestions or dogs with heart disease -> call your vet.
What should I do if my dog ate thyroid medication (levothyroxine)?
Usually not dangerous in small amounts. Watch for the symptoms below for the next 24 hours. Call your vet if symptoms appear, the amount was large, or your dog is very small, old, or ill.
Who can I call for help?
ASPCA Animal Poison Control (888) 426-4435 or Pet Poison Helpline (855) 764-7661, both 24/7 (fees may apply), or your nearest emergency vet.
Dose guidance
No reliable dog-specific threshold is published for home use, so any amount should be discussed with your vet or a poison hotline.
Sources
Last verified against these sources: 2026-10-13. Where sources disagree, PawPanic uses the more conservative guidance.
Also known as: synthroid, levothyroxine · Category: Medication · Last reviewed 2026-10-14