Is Furosemide (Lasix) Safe for Dogs?
Why it’s a problem
Furosemide is a powerful loop diuretic that flushes water and electrolytes out of the body. Vets do prescribe it for heart disease, but an unsupervised dose can push a dog toward dehydration, low potassium, and kidney strain, especially in small or senior dogs. A single large accidental dose is rarely fatal but can make a dog seriously ill.
How to keep your pet safe
Store the bottle high and closed, and keep pill organizers out of reach. Never share your prescription with a dog, even an older one with a cough or heart murmur. If your dog has prescribed furosemide, ask the vet before changing the schedule.
Warning signs to watch for
Excessive urination, intense thirst, vomiting, diarrhea, lethargy, weakness or wobbliness, loss of appetite; severe cases show dehydration and stumbling.
When to call the vet
Call your vet or a pet poison hotline for guidance with the tablet strength and your dog’s weight. Keep fresh water available, but do not force large volumes. Expect monitoring for a day, since diuretic effects can last many hours.
Common questions
My dog ate one of my Lasix pills — is that serious?
It can be, especially for small or older dogs, because the drug drains fluid and electrolytes. Call your vet or a pet poison hotline with the dose and timing rather than waiting.
My dog is peeing constantly after eating furosemide — will it stop?
The diuretic effect can last several hours. Keep water available and call your vet, since prolonged loss of fluid and potassium may need bloodwork and supportive care.
More medications hazards for dogs
This page is general educational information, not a substitute for professional veterinary advice. Every pet is different — if your animal ate or touched something concerning, contact your veterinarian or a pet poison hotline right away. In the US: Pet Poison Helpline (855) 764-7661, ASPCA Animal Poison Control (888) 426-4435 (fees may apply).