High Blood Pressure (Hypertension) in Cats

What Is Hypertension in Cats?

Hypertension in cats describes high blood pressure that is present throughout the entire body.

When a cat’s heart contracts, it pushes blood throughout the body and creates pressure on the walls of the arteries. This pressure is called systolic blood pressure (SBP). When the heart relaxes and fills with blood, the pressure on the artery walls is called diastolic blood pressure (DBP). So blood pressure is a measurement of the amount of pressure on the artery walls.

A cat’s blood pressure is measured in the same way as a human’s, with the systolic number over the diastolic number, measured in millimeters of mercury, or mmHg. A human’s normal blood pressure is 120/80 mmHg.

In cats, the diastolic blood pressure measurement, or the bottom number, is less reliable and considered a less important component of hypertension. So hypertension in cats is typically diagnosed on the basis of an elevated systolic blood pressure, or top number.¹

Feline hypertension is generally diagnosed when the SBP is greater than 160 mm Hg or if the SBP is greater than 150 mmHg and there is clear evidence of organ damage due to hypertension.

Symptoms of High Blood Pressure in Cats

Early signs of high blood pressure in cats are often not noticeable to pet parents and may only be detected by routine blood pressure measurement.

Unfortunately, if cats are not routinely screened for high blood pressure or common diseases that cause high blood pressure, they will only show noticeable symptoms once significant damage has already been done to their organs. The organs that are damaged by hypertension in cats are the eyes, brain, nervous system, kidneys, and heart.

Usually, a pet parent will first notice something wrong with their cat’s eyes, and this is what will prompt them to seek veterinary attention. Symptoms include:

• Fixed, dilated pupils

• Blood in the globe (clear chamber) of the eye

• Bumping into objects

• Sudden blindness

Blindness and dilation of the pupils are often due to retinal detachment. Unless hypertension in cats is treated very promptly and aggressively, vision loss is often permanent.

Symptoms of brain damage due to feline hypertension include:

• Abnormal behavior

• Disorientation

• Depression

• Seizures

Signs of kidney damage that may be worsened with hypertension include:

• Decreased appetite

• Vomiting

• Weight loss

• Lethargy

• Increased water intake

• Frequent urination

Signs of heart disease due to hypertension include:

• Abnormal heart sounds or murmurs found during a veterinary examination

• Less likely: Rapid, shallow breathing, paralysis, or sudden death due to congestive heart failure

Causes of High Blood Pressure in Cats

In 80% of cases, high blood pressure in cats is due to or associated with an underlying disease. This is called secondary hypertension. These are the two most common underlying conditions:

• Chronic kidney disease (CKD) is the most common disease associated with hypertension in cats and is found in up to 74% of cats with hypertension. ¹

• Hyperthyroidism, a disease caused by a tumor on the thyroid gland (usually benign), is also commonly present in cats with hypertension.

Uncommon diseases that are linked to a higher risk of feline hypertension include hyperaldosteronism, hyperadrenocorticism (Cushing’s disease), diabetes mellitus, and pheochromocytoma. These diseases are diagnosed most frequently in senior and geriatric cats. Certain medications such as steroids and phenylpropanolamine may also lead to high blood pressure in cats.

About 20% of cats have idiopathic hypertension, meaning that an underlying cause is unable to be found. A portion of these cats are likely in the very early stages of chronic kidney disease, before laboratory abnormalities can be detected. ¹  

How Vets Diagnose Hypertension in Cats

Veterinary teams measure blood pressure in cats in a way that’s similar to measuring a human’s blood pressure. A cuff is placed around your cat’s front leg, back leg, or tail, and then it’s inflated. The vet will use either a doppler or oscillometric blood pressure device to take the readings.

Cats can easily become scared at the vet’s office and experience “white coat syndrome,” which can lead to stress-related hypertension. To avoid getting a false diagnosis of hypertension due to stress, your veterinarian will likely take your cat’s blood pressure reading in a quiet area and will try to allow your cat to relax prior to taking the measurements.

Typically, at least five readings will be taken during the visit and averaged together. In addition, unless it is obvious that your cat is hypertensive—for example, there are signs consistent with hypertension, such as retinal detachment—your veterinarian will repeat blood pressure measurements on at least two separate occasions before diagnosing hypertension.

Treatment for High Blood Pressure in Cats

As in humans, high blood pressure in cats is treated with oral medications. Amlodipine, a calcium channel blocker, is the drug of choice used to treat feline hypertension. It comes in a pill form and is given orally once daily.

If you have a hard time giving pills to your cat, your veterinarian may have the medication compounded into a liquid. The goal of treatment is to minimize the symptoms associated with organ damage due to high blood pressure and to reduce your cat’s blood pressure to less than 150 mmHg.

In some cases, additional medications, such as ACE inhibitors or telmisartan may be necessary.

Aside from using medications to help lower your cat’s blood pressure, your veterinarian will need to run laboratory tests to detect any underlying diseases that contribute to hypertension.

This typically includes a complete blood cell count, chemistry panel, thyroid hormone levels, and urine testing. As stated previously, about 80% of cats with hypertension have an underlying disease, and treating the underlying disease is an important component of managing hypertension and increasing your cat’s life span.

Pet parents do typically notice an improvement in their cat’s demeanor and energy levels after starting therapy for hypertension. However, if your cat had vision loss at the time of diagnosis, it may be a permanent consequence of hypertension.

Since hypertension is often unnoticeable until it has been present long enough to cause significant organ damage, the International Society of Feline Medicine (ISFM) recommends routine blood pressure screening for cats as follows:¹

• Healthy senior cats (7-10 years of age): every 12 months

• Healthy geriatric cats (11+ years of age): every 6-12 months

• Cats with CKD, hypertension, or other diseases that increase the risk of hypertension, as well as those with signs of hypertensive organ damage: At time of diagnosis, and then every 3-6 months