Furosemide side effects in cats

Updated November 21, 2016

Furosemide is a medication used in cats for a variety of health issues including heart failure, high blood pressure and pulmonary oedema. This medication is a diuretic drug, meaning that it aids in preventing excessive fluid build-up in the body. Furosemide can also go by the brand names of Lasix and Diuride. In some parts of the world it goes by the name of frusemide. Like any medication, furosemide has several potential side effects in felines. If any of these signs occur, veterinary care should be sought immediately.

Allergic Reactions

Allergic reactions to furosemide may be found in some cats. Symptoms of an allergic reaction include difficultly breathing, hives and swelling of the face, tongue, lips or throat.


Cats who are taking furosemide may become anaemic. Anemia is a term describing a decrease of red blood cells. Cats who are suffering from anaemia may display symptoms such as weakness, loss of appetite, vomiting and weight loss.

Gastrointestinal Problems

Furosemide can have several gastrointestinal side effects for cats including vomiting, nausea, stomach pain, constipation or diarrhoea.

Hearing Loss

Some cats may suffer from hearing loss after being given high dosages of this medication. The owner may notice that their cat is not responding to his name or does not react to being approached from behind, both of which can indicate hearing loss.


Jaundice is a severe side effect which indicates the liver is failing and waste is building up within the body. Jaundice is characterised by yellowing of the skin, eyes and mucus membranes of the cat.

Skin Lesions

Lesions, often described as being similar in appearance to a bull's-eye, may begin to appear in some cats taking furosemide.


Furosemide can cause the cat's skin to become more sensitive to direct sunlight and lead to sunburn in some cats.


Cats taking furosemide may experience a change in the colour of their urine; the urine will be darker than normal. Some cats may experience an increase in urination, although this is to be expected as furosemide is a diuretic.

Weakness and Pain

Weakness can occur in some cats who are taking furosemide. These cats may also suffer from muscle pain.

Overdose Symptoms

Cats who have too much furosemide in their system may suffer from weakness, dizziness, fainting, loss of appetite and confusion.

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