Is Furosemide (Lasix) Safe for Cats?
Why it’s a problem
Cats are small, so a human tablet delivers a large relative dose of this potent diuretic. The resulting fluid and potassium loss can leave a cat weak and, in cats with kidney or heart disease, genuinely sick. Vets prescribe furosemide for heart conditions, but with feline-specific dosing and monitoring.
How to keep your pet safe
Keep furosemide in a closed cabinet and pick up any dropped tablet at once. Do not dose a cat from your own prescription, even if the cat has a heart condition. Ask your vet how to handle missed or doubled doses of any prescribed diuretic.
Warning signs to watch for
Large amounts of urine, excessive drinking, vomiting, lethargy, hiding, weakness, wobbly gait, dehydration.
When to call the vet
Call your veterinarian or a pet poison hotline and report the dose and timing. Most cats need observation and possibly electrolyte bloodwork, which only a clinic can do. Never try to rehydrate a sick cat by squirting water into its mouth.
Common questions
Is Lasix toxic to cats?
It is more depleting than deadly — the main danger is fluid and potassium loss that can seriously weaken a small cat. Any accidental dose deserves a call to your vet or a pet poison hotline.
My cat is on furosemide and skipped a dose — can I double the next one?
Never double up without asking your vet. Extra diuretic can cause dehydration and electrolyte crashes even in a cat that needs the drug.
More medications hazards for cats
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).