What Is Feline Hypertension?
Hypertension — persistently elevated blood pressure — is one of the most commonly diagnosed conditions in middle-aged and older cats. A systolic blood pressure reading above 160 mmHg is considered hypertensive in cats, and readings above 180 mmHg are classified as severely hypertensive. Left untreated, high blood pressure causes progressive and sometimes irreversible damage to several vital organs, including the eyes, kidneys, heart, and brain.
Unlike in people, primary hypertension (high blood pressure with no underlying cause) is rare in cats. The vast majority of feline hypertension cases are secondary, meaning they arise as a consequence of another disease. This distinction matters because managing the underlying condition is just as important as lowering the blood pressure itself.
The Most Common Underlying Causes
Hyperthyroidism
An overactive thyroid gland is one of the leading causes of secondary hypertension in cats. Hyperthyroidism increases heart rate and cardiac output, which in turn drives blood pressure upward. Many cats with newly diagnosed hyperthyroidism are already hypertensive by the time they are seen by a vet. Importantly, treating the thyroid disease does not always resolve the hypertension, so blood pressure must be monitored independently even after successful thyroid treatment.
Chronic Kidney Disease
Chronic kidney disease (CKD) is the other predominant cause. Damaged kidneys struggle to regulate fluid balance and the renin-angiotensin-aldosterone system, leading to fluid retention and vascular resistance — both of which push blood pressure up. Cats with CKD should be screened for hypertension at every veterinary visit, as the two conditions accelerate each other's progression.
Other Causes
Less common causes include hyperaldosteronism (Conn's syndrome), diabetes mellitus, polycythaemia (an excess of red blood cells), and certain medications such as corticosteroids or erythropoietin.
Target Organ Damage: What High Blood Pressure Does to the Body
The Eyes
Ocular damage is often the most dramatic and visible consequence of feline hypertension. High pressure within the blood vessels of the retina causes them to haemorrhage or rupture, leading to retinal detachment. Owners may notice that their cat suddenly walks into furniture, appears startled in dim lighting, or has visibly enlarged, dilated pupils that do not respond normally to light. This sudden onset of blindness is a veterinary emergency. If treatment is started within 24 to 48 hours, there is a reasonable chance of partial vision recovery. Beyond that window, blindness is usually permanent.
The Brain and Nervous System
Hypertension can damage small blood vessels in the brain, causing neurological signs such as disorientation, seizures, head pressing, circling, or sudden changes in personality and behaviour. These episodes can easily be mistaken for other neurological conditions, making blood pressure measurement an essential part of any neurological work-up in an older cat.
The Heart
Sustained high blood pressure forces the heart to work harder with every beat, causing the left ventricular wall to thicken — a condition known as hypertensive cardiomyopathy. This can eventually lead to heart failure if left unmanaged.
The Kidneys
High blood pressure accelerates the destruction of kidney tissue, creating a damaging cycle in cats with existing CKD. Glomerular hypertension — elevated pressure within the tiny filtering units of the kidney — causes progressive scarring and loss of function.
Diagnosing Hypertension: The Importance of a Calm Environment
Blood pressure in cats is typically measured using a Doppler or oscillometric device, with a small inflatable cuff placed around the leg or tail. The procedure is non-invasive and generally well tolerated, but accuracy depends heavily on the environment and the cat's stress level at the time of measurement.
Cats are highly prone to what is known as white coat hypertension — a temporary spike in blood pressure triggered by the stress of being in a veterinary clinic. A nervous or agitated cat can produce falsely elevated readings that do not reflect its true resting blood pressure. To account for this, vets will typically take multiple readings over a period of several minutes, discard the first few measurements, and allow the cat to settle in a quiet room before beginning. Ideally, the cat should be on the examination table without being restrained, and the room should be free from sudden noises and unfamiliar smells. In some cases, a vet may ask the owner to take blood pressure readings at home using a validated portable device.
A diagnosis of hypertension is generally not made on a single reading. Most clinicians require consistently elevated readings on at least two separate visits before committing to treatment, unless there is already clear evidence of target organ damage.
Treatment
Amlodipine: First-Line Medication
Amlodipine besylate, a calcium channel blocker, is the drug of choice for managing hypertension in cats. It works by relaxing the smooth muscle in arterial walls, reducing vascular resistance and lowering blood pressure effectively. Amlodipine is given orally once daily, usually as a small tablet or a compounded liquid or transdermal gel. Most cats respond well, and blood pressure often begins to fall within days of starting treatment.
The dose is adjusted based on follow-up readings, and regular monitoring is essential — typically every two to four weeks initially, then every three to six months once the blood pressure is stable.
Addressing the Underlying Disease
In cats with hyperthyroidism, treatment with radioactive iodine, anti-thyroid medications (such as methimazole), or surgical thyroidectomy is also required. In cats with CKD, dietary management, hydration support, and phosphate binders may all form part of the broader treatment plan.
ACE Inhibitors
Drugs such as benazepril or trandolapril are sometimes used alongside amlodipine, particularly in cats with significant proteinuria or CKD. They help reduce protein loss in the urine and provide additional kidney protection, though they are less effective than amlodipine at reducing blood pressure on their own in cats.
Monitoring and Long-Term Management
Feline hypertension is a lifelong condition in most cats. Once medication is started, it should not be stopped without veterinary guidance, even if the cat appears well. Regular check-ups are essential to ensure the blood pressure remains well controlled and to adjust treatment as the underlying disease progresses.
Owners can play an important role by learning to recognise early warning signs — particularly any sudden change in vision or behaviour — and seeking urgent veterinary attention if these occur. With appropriate management, many hypertensive cats live comfortably for years after diagnosis.