Understanding the Uses, Dosage, and Side Effects of This Diuretic

dog drinking water

Jason Donnelly


  1. On this page

    • What is furosemide?

    • Uses

    • Dosage

    • Side effects

    • Overdose

    • Precautions and Warnings

If your vet has prescribed furosemide for you, you’ve probably been dealing with a pretty serious health issue with your dog. We feel you. Any health condition can be scary, but when you hear your vet say something like “fluid in chest” or “heart failure” you are bound to be concerned.

Fortunately, furosemide for dogs can help treat a handful of conditions when closely monitored by a veterinarian. Here’s what you need to know.

What is furosemide?

Furosemide is a diuretic commonly used in veterinary medicine. It is often prescribed to treat heart disease and other conditions that cause the body to retain fluids. Common brand names for furosemide include Lasix and Salix, but generic forms are also available by prescription from your veterinarian.

Furosemide and similar diuretics can reduce various forms of edema (accumulation of fluid in the tissues) and relieve many associated symptoms. The drug works in the kidneys, a set of two complex organs responsible for maintaining hydration, electrolyte balance, and blood pressure through filtration and excretion systems. Loop diuretics such as furosemide work by passing more fluids, minerals and electrolytes through the kidneys, thus producing more urine. This draws fluid that has accumulated in the body into the bloodstream, replacing fluid that has passed through the kidneys.

What is furosemide used for in dogs?

Furosemide is used to remove any excess fluid from the body by helping your dog to urinate more frequently. The fast-acting medication typically increases your dog’s urination within an hour or two, a sign that the medication is working to expel excess fluid.

Furosemide can be beneficial, even life-saving, for dogs with several health conditions, including:

Congestive heart failure

Congestive heart failure is a form of heart disease that often causes fluid buildup or congestion in the chest, abdominal cavities, or lung tissue (a condition called pulmonary edema). This fluid buildup can prevent the dog from breathing properly.

Since furosemide helps the kidneys expel fluid from the bloodstream, it may allow excess fluid in the tissues to enter the bloodstream and leave the body through urine.


Edema is swelling caused by excess fluid in the tissues of the body. Furosemide can help remove fluid from body cavities or other tissues even if the cause is not heart failure.


In addition to its diuretic properties, furosemide may also act as an airway dilator to reduce coughing in dogs. Dogs with chronic bronchitis may benefit from furosemide, but it is not usually used alone to treat this condition.

kidney disease

Kidney disease causes uremia, a buildup of waste products in the blood that are normally eliminated by the kidneys. Furosemide helps the kidneys produce more urine to filter out these wastes. Also, furosemide can be used in combination with other medicines to stimulate the production of urine if the kidneys do not produce enough.


Calcium is one of the minerals that passes through the kidneys, and furosemide encourages the organs to evacuate more of it. Thus, furosemide can reduce blood calcium levels if they become dangerously high (a condition called hypercalcemia). Other drugs, such as prednisone, can be used with furosemide to promote calcium excretion.


Furosemide may also be useful in reducing high potassium blood levels (hyperkalaemia). This condition is often linked to kidney disease.

Furosemide Dosage for Dogs

Furosemide is available in oral and injectable form. Injections are usually given in the hospital, but your veterinarian may prescribe tablets or liquid to give at home.

The tablets are available in multiple strengths so your veterinarian can prescribe an accurate dose. The liquid form is useful for small dogs or those who don’t take pills well. And while furosemide is available in both veterinary and human formulations, both are OK to give Fido.

Your veterinarian calculates your dog’s furosemide dose based on his weight and the specific condition being treated. This is usually between 1 and 4 milligrams per kilogram of body mass every 8 to 12 hours. Accurate dosing is important to prevent adverse effects, so do not adjust your dog’s dose without first talking to your veterinarian.

If you miss a dose of furosemide, give it immediately unless the next dose is almost due. Then resume the recommended program. Do not double the doses.

Wash your hands after handling furosemide so that you don’t absorb this medicine into your skin. If you are allergic to sulfonamides (sulfonamides), wear gloves when handling.

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Side Effects of Furosemide for Dogs

Furosemide can cause several side effects in dogs, some worse than others. Make sure your dog drinks enough water while taking furosemide to reduce the likelihood of some of these effects. The most common side effects of furosemide in dogs include:

  • Increased urination (this is normal, but contact your vet if it’s extreme)

  • Increased thirst

  • Dehydration

  • Electrolyte imbalances (especially low sodium)

  • Mineral deficiencies (low in calcium, magnesium or potassium)

  • Diarrhea

  • Constipation

The following side effects are less common in dogs but can be serious:

  • Anemia (low number of red blood cells)

  • Leukopenia (low white blood cell count)

  • Lethargy

  • Weakness

  • Hustle

  • rapid heartbeat

  • Hypoglycemia (low blood sugar)

  • Hearing loss (at very high doses)

Contact your veterinarian if you notice these or any other unusual signs in your dog while taking furosemide. It is important that your veterinarian monitors your dog regularly during treatment. Your dog will need follow-up exams and lab work periodically to prevent serious side effects.

Can dogs overdose on furosemide?

It is possible for dogs to overdose on furosemide, especially if they get all the way through the bottle. always keep everything medications away from your dog to prevent toxicity.

An overdose of furosemide can lead to serious problems with hydration and electrolyte balance, as well as central nervous system problems (such as seizures and even coma) and heart failure. Contact a veterinarian immediately if your dog accidentally receives too much furosemide. You can call your local veterinarian, animal emergency service, or pet poison control service like ASPCA Animal Poison Control at (888) 426-4435 or the pet poison helpline at (855) 764-7661 for professional advice.

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Precautions and Warnings

Furosemide should not be used in dogs with anuria, a condition in which the kidneys can no longer produce urine. Dogs with kidney disease should be closely monitored during treatment. Furosemide should be used with caution in dogs with a history of diabetes mellitus, liver disease, and electrolyte imbalance.

Several drug interactions have been reported or are theoretically possible in dogs on furosemide. Be sure to tell your veterinarian about all medications and supplements you give your puppy. The following drugs may interact with furosemide:

  • ACE inhibitors like enalapril and benazepril can cause high blood pressure.

  • Aminoglycosides like gentamicin and amikacin can increase the risk of hearing loss.

  • Amphotericin B may increase the risk of hyperkalemia and kidney damage.

  • Corticosteroids like prednisone can increase the risk of gastrointestinal ulcers and hyperkalemia.

  • Digoxin, also used for heart disease, may increase the risk of toxicity when used in combination with furosemide.

  • Some muscle relaxants may work differently when taken with furosemide.

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