My cat is struggling to breathe or breathing with its mouth open: what to do now
Dogs pant to cool down; cats almost never do. A cat breathing with its mouth open, moving its belly a lot as it breathes or taking more than forty breaths a minute at rest needs a vet without delay. This guide helps you recognise it, do the right thing in the first few minutes and understand what will happen at the clinic.
Why it is always serious in cats
Cats are experts at hiding illness, and the respiratory system is no exception: they compensate for days until they can no longer cope. By the time an owner notices their cat breathing oddly, the problem has usually been going on for a while. A cat short of breath also has very little reserve: the stress of travelling, being restrained or a rough examination can be enough to tip it over the edge. That is why feline vets insist on two things: do not wait to see if it passes, and handle the cat as little as possible. The only reasonable exception is brief panting after a very energetic game or a stressful journey in a young cat, which should stop within a few minutes of rest.
How to count its breaths
It is the most useful tool you have, and it costs nothing. With the cat asleep or lying quietly, count how many times its side rises and falls in thirty seconds and multiply by two. A healthy cat at rest is usually below about thirty breaths a minute, and many are around twenty. More than forty at rest, consistently, is a reason to see the vet that same day. If your cat has a diagnosed heart condition, the vet will ask you to count often at home and give you a number above which to call: it is the best way to catch a decompensation in time. You can note it on your phone, or use one of the apps designed for it.
Warning signs
Open-mouth breathing at rest. Exaggerated belly movements with every breath, as if pushing the air out. Sitting or lying on its chest with elbows out and neck stretched, refusing to lie on its side. Bluish, grey or very pale gums or tongue. Noises when breathing, such as whistling, new snoring or gurgling. Restlessness, not being able to get comfortable or, conversely, being very still and hidden. Any one of these signs on its own justifies a trip to the emergency vet. If the cat also has one or both hind legs cold and is not moving them, it may be an arterial thromboembolism, a complication of heart disease that is a serious emergency.
What to do in the first few minutes
Call your clinic or an emergency veterinary hospital to say you are on your way: that way they can have oxygen ready. Put the cat in the carrier with as little handling as possible, ideally one that opens at the top or comes apart, so it does not have to be dragged out at the clinic. If it struggles a lot, you can cover it with a towel and put it in with the towel. Keep the car cool, without strong heating, and do not take it out of the carrier during the journey. Do not force water or food on it, do not try to open its mouth or give it any medicine, and do not waste time searching online. If you know its breathing rate, tell the vet when you arrive.
Causes: the heart and fluid in the chest
Heart failure is one of the most common causes in adult and older cats, almost always due to a cardiomyopathy, often the hypertrophic form. When the heart cannot keep up, fluid builds up in the lungs (pulmonary oedema) or around them (pleural effusion), and the cat breathes faster and faster. Many of these cats had no previous symptoms, and sometimes the trigger is stress, an anaesthetic, intravenous fluids or a course of corticosteroids. Pleural effusion can also be due to a chest infection (pyothorax, often after a bite), tumours such as mediastinal lymphoma, or the wet form of feline infectious peritonitis.
Causes: airways, trauma and others
An asthma attack can cause acute breathing difficulty in a cat that had been coughing now and then for months. Trauma, especially a fall from a balcony or being hit by a car, can cause pneumothorax, lung contusion or a diaphragmatic hernia, sometimes without visible external wounds. Upper airway obstructions (polyps, foreign bodies, tumours in the nose or larynx) cause loud breathing noises. And some causes are not in the lungs at all: severe pain, serious anaemia, acidosis from uncontrolled diabetes or heatstroke also speed up breathing. Flat-faced breeds breathe less well to begin with, and in them any heat or exertion shows sooner.
What the vet will do
The first step is to stabilise, not to diagnose. With a cat in respiratory distress, the team usually starts with oxygen in an oxygen cage or box, sometimes with a mild sedative to reduce stress, and a very brief examination. Many clinics then do a quick chest ultrasound, which with the cat barely restrained shows whether there is fluid in the chest or the heart is enlarged. If there is pleural effusion, draining it with a needle (thoracocentesis) relieves the cat within minutes and also allows the fluid to be analysed. X-rays, a full echocardiogram and blood tests are done once the cat is stable enough to tolerate them. Not doing everything at once is good medicine, not slowness.
What it costs in Spain in 2026
As a guide, emergency care with oxygen and initial stabilisation can cost around €150 to €400, and somewhat more out of hours. A thoracocentesis with fluid analysis, €100 to €250. Chest X-rays, €60 to €150. An echocardiogram with a cardiologist, €150 to €300. Hospitalisation in oxygen with monitoring, €150 to €400 a day at a hospital with a 24-hour service. An episode of heart failure with two or three days in hospital can easily exceed €1,000, followed by long-term treatment of €30 to €80 a month plus check-ups. If your cat belongs to a breed predisposed to heart disease, it is worth checking what your insurance covers.
After the scare: living with the cause
The outlook depends entirely on the cause. A well-treated asthmatic cat can live for many years with an excellent quality of life. A cat with heart failure will need lifelong medication, check-ups and daily monitoring of its breathing at home, and its prognosis is more guarded, although some cats live well for a long time. A pneumothorax from a fall usually resolves if treated in time. What nearly all these cases have in common is that home monitoring makes the difference: counting breaths, not skipping medication, avoiding stress and heat, and calling as soon as the number goes up.
Prevention and early detection
Many of these emergencies can be anticipated. In breeds predisposed to cardiomyopathy (Maine Coon, Ragdoll, Sphynx, British Shorthair, Bengal, among others), or in any cat found to have a murmur or an abnormal rhythm at a check-up, an echocardiogram can detect the problem before it shows itself. Before an anaesthetic in an older cat or one with a murmur, it is wise to assess the heart. Netting on windows and balconies prevents trauma from falls. No smoke or aerosols at home. And the habit of knowing your cat’s resting breathing rate, even when it is healthy, lets you react within hours rather than days.
A cat breathing with its mouth open, moving its belly a lot or taking more than about forty breaths a minute at rest needs emergency care. Call the clinic, put it in the carrier with minimal handling and give it nothing. The most common causes are the heart, fluid in the chest, asthma and trauma.
Educational content from Michipedia, translated from the Spanish original. It does not replace the advice of a vet or a feline behaviour specialist. Every cat is an individual.