Cyanosis in Cats

Brittany Kleszynski, DVM
By Brittany Kleszynski, DVM on Feb. 22, 2024
A cat's mouth is examined by their vet.

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In This Article


What Is Cyanosis in Cats?

Cyanosis is relatively common in cats and causes discomfort. Cyanosis refers to the lack of oxygen in blood, which causes blue discoloration to the mucous membranes and skin.

Hemoglobin is the part of the blood that normally carries oxygen to the tissues throughout the body. In cats with cyanosis, hemoglobin traveling through blood vessels is deprived of oxygen. Oxygenated blood is red in color and deoxygenated blood is blue, which is why cyanosis causes blue discoloration.

Cyanosis is always a symptom of another underlying health issue, most commonly lung or heart disease, but a variety of health conditions can cause it. Certain congenital (present at birth) heart defects make the condition more likely, since blood can bypass the lungs where it would have received oxygen before it is sent elsewhere in the body.

Toxins, blood clots, and low body temperature (hypothermia) are also possible causes of cyanosis in cats.

Cyanosis in cats is a medical emergency that, if left untreated, is fatal.

Cats experiencing cyanosis need immediate veterinary intervention to improve oxygenation of their blood and prevent serious damage to their organs. This condition typically has a poor prognosis, especially if the underlying cause is heart or lung disease.

Symptoms of Cyanosis in Cats

Symptoms of cyanosis in cats can result in several concerning symptoms, including:

Causes of Cyanosis in Cats

Any disease or condition that decreases oxygen in the blood has the potential to lead to cyanosis in cats. Some of the most common causes include:

  • Congenital heart defect—Heart defects may not allow the body to receive enough oxygen. Examples of heart defects that may cause cyanosis in cats include patent ductus arteriosus, ventricular septal defects, and atrial septal defects. Cyanosis due to congenital heart defects is most common in young cats.

  • Toxin ingestion—When certain toxins are ingested, hemoglobin loses its ability to carry oxygen throughout the body, resulting in cyanosis. Acetaminophen (Tylenol®) is an example of a medication that is toxic to cats and can lead to cyanosis.

  • Electrical shock—If a cat chews on an electrical cord, electrical shock may occur, leading to fluid buildup in the lungs and difficulty breathing.  

  • Trauma or inflammation—Anything that causes trauma or inflammation to the brain, lungs, or chest cavity can result in cyanosis due to the body’s inability to oxygenate the blood appropriately.

  • Brachycephalic obstructive airway syndrome—Cats with a flat face have structural differences in their upper airways, such as a narrow trachea, which causes them to have poor oxygenation compared to other cats. Burmese, Persian, and Himalayan cats are predisposed to this condition.

  • Saddle thrombus—When a blood clot gets trapped in a major blood vessel it can cut off circulation to the hind legs, resulting in bluish discoloration to the paw pads.

  • Hypothermia—When a cat’s body temperature reaches dangerously low levels, blood vessels in the limbs constrict to allow more blood to reach vital organs, such as the heart and brain. As a result, the cat’s skin can turn blue in various areas, such as the lips and limbs.

How Veterinarians Diagnose Cyanosis in Cats

To diagnose cyanosis in cats, a veterinarian will conduct a physical exam, paying special attention to the color of the mucous membranes and skin, as well as assessing the heart and lungs.

Pet parents should provide a detailed history, including when symptoms started, any pre-existing medical conditions, and a list of any medications the cat is taking.

To measure the amount of oxygen in a cat’s blood, a veterinarian may complete the following tests:

  • Pulse oximetry—This is a simple, noninvasive test where a special device is placed onto a cat’s ear or in between their paw pads to measure the oxygen in the blood. This number is normally at 100%. Cats with cyanosis have levels less than 90%.

  • Arterial blood gas analysis—A sample of blood is taken from the cat’s artery and a machine identifies how much oxygen is present within the blood.

Additional tests, such as imaging and bloodwork, can be done to diagnose the underlying cause of the cyanosis.

Treatment of Cyanosis in Cats

Since cyanosis in cats results from another underlying condition, treatment focuses on management of the underlying condition first. Treatment varies greatly because of this.

The most important treatment is oxygen therapy, which is administered at the veterinary hospital to improve oxygenation of the blood and alleviate any respiratory symptoms that may be present.

Other treatments may include the following:

  • Thoracentesis—If trauma has occurred, fluid may need to be removed from the chest cavity to allow the cat to breathe more effectively.

  • Surgery—If the cat is diagnosed with a heart defect or a blood clot, surgery may be able to correct the problem and improve oxygenation within the blood.

  • Toxin antidote—If toxin ingestion is suspected, specific medications can be given to counteract its effects. For example, n-acetylcysteine is used for treating acetaminophen toxicity in cats.

  • Diuretics—Medications such as furosemide can be given to remove excess fluid from a cat’s lungs to allow for better oxygenation.

  • Supplemental heat—Cats who have dangerously low body temperatures can be safely warmed at the veterinary hospital using warm blankets and intravenous fluids.

Additional treatments may be recommended as deemed appropriate by the veterinarian. Most cats with cyanosis are hospitalized for supportive care.

Recovery and Management of Cyanosis in Cats

Recovery from cyanosis in cats depends on the underlying cause.

For example, if severe heart or lung disease is present, the prognosis is poor and most cats succumb to cyanosis quickly. However, if a cat has ingested acetaminophen, early diagnosis and treatment with antidotes can provide a good prognosis in otherwise healthy cats.

Cats who are sent home after being diagnosed and treated for cyanosis should be monitored closely. Pet parents should follow the veterinarian’s instructions for follow-up care and prescription medications carefully during recovery.

Prevention of Cyanosis in Cats

Many causes of cyanosis in cats are not preventable. Certain conditions, such as congenital heart defects, can only be managed with medications or surgery depending on the severity.

However, certain causes of cyanosis can be prevented. Keeping potential toxins safely out of reach and not allowing cats access to extension cords that can be chewed are important preventative measures.

Overall, regular preventive veterinary care is most important for the  health and well-being of cats. These checkups allow veterinarians to catch any health problems early on so that appropriate treatment can be started before they worsen in severity.

Brittany Kleszynski, DVM


Brittany Kleszynski, DVM


Dr. Brittany Kleszynski is a veterinarian and freelance medical writer who specializes in creating meaningful content that engages readers...

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