Understanding Feline Hypertension
High blood pressure, or hypertension, is one of the most underdiagnosed conditions in older cats. Unlike dogs, cats rarely show obvious outward signs until the damage is already done. By the time a cat owner notices something is wrong, organs including the eyes, kidneys, heart, and brain may have been under pressure for months or even years. Regular blood pressure monitoring from around age seven is not an overreaction — it is simply good preventive medicine.
Normal systolic blood pressure in cats sits below 140 mmHg. Readings between 140 and 159 mmHg are considered mildly elevated, 160 to 179 mmHg moderately elevated, and anything above 180 mmHg is classified as severe hypertension requiring urgent intervention. These thresholds are not arbitrary; they are tied to the likelihood of target organ damage at each level.
Why Cats Develop High Blood Pressure
Hypertension in cats almost always arises secondary to another condition. Chronic kidney disease is the most common underlying cause, accounting for roughly 20 to 65 per cent of hypertensive cats depending on the study. The relationship runs in both directions — damaged kidneys raise blood pressure, and raised blood pressure accelerates kidney damage, creating a damaging cycle that is difficult to interrupt once established.
Hyperthyroidism is the second major culprit, particularly in cats over ten years old. An overactive thyroid increases cardiac output and peripheral vascular resistance, both of which push blood pressure upward. Interestingly, treating hyperthyroidism without monitoring blood pressure can sometimes unmask worsening kidney disease, so the two conditions must be managed together carefully.
Less commonly, diabetes mellitus, hyperaldosteronism, and phaeochromocytoma can drive hypertension. Primary hypertension without an underlying cause does exist in cats but is far rarer than in humans.
Recognising the Signs
The nickname "silent killer" exists for a reason. Many cats with hypertension show no symptoms until a crisis occurs. When signs do appear, they tend to reflect the organ systems under greatest stress.
Ocular Signs
The eyes are often the first place a vet notices hypertensive damage. Sudden blindness, dilated and unresponsive pupils, or visible bleeding within the eye are all possible. Retinal detachment secondary to hypertension can happen extremely rapidly — sometimes within hours of a significant pressure spike. Any cat that suddenly walks into walls, seems disoriented in familiar spaces, or has visibly changed pupils needs same-day veterinary assessment.
Neurological Signs
High blood pressure can cause small haemorrhages in the brain, leading to head tilting, circling, wobbling, or sudden-onset seizures. These episodes are frequently mistaken for strokes or inner ear problems, and while the distinction matters for long-term management, the immediate response should always be urgent veterinary care.
Cardiac and Renal Signs
A heart murmur detected for the first time in a senior cat may have a hypertensive component. Cats may also drink and urinate more than usual, reflecting the interplay between blood pressure and kidney function. Nosebleeds, though uncommon in cats generally, can occasionally signal severe hypertension.
Diagnosis and Monitoring
Blood pressure measurement in cats is typically done using a Doppler device or an oscillometric monitor designed for small patients. The process requires the cat to be as calm as possible, which means most veterinary practices allow a settling period before taking readings. A single elevated reading is not sufficient for diagnosis — guidelines recommend five or more readings taken in a quiet environment, with the highest and lowest discarded before averaging the remainder.
Because white coat hypertension exists in cats just as it does in humans, some vets use home monitoring devices or make house calls for particularly anxious patients. Context matters enormously when interpreting results.
Alongside blood pressure measurement, a diagnostic workup should include a full blood panel, urinalysis with urine protein to creatinine ratio, thyroid hormone levels in cats over seven, and ideally an echocardiogram to assess cardiac changes.
Treatment Options
Amlodipine, a calcium channel blocker, is the first-line treatment for feline hypertension and has a strong evidence base supporting its use. It is effective, generally well tolerated, and available in formulations that can be compounded into transdermal gels for cats resistant to oral medication. Most cats show a meaningful reduction in blood pressure within one to two weeks of starting treatment.
If amlodipine alone does not achieve adequate control, telmisartan — an angiotensin receptor blocker — is commonly added. Telmisartan also has the advantage of reducing protein loss through damaged kidneys, making it particularly useful in cats with concurrent chronic kidney disease.
Treating the underlying condition matters as much as addressing the blood pressure directly. Hyperthyroid cats on appropriate medication often see their blood pressure improve substantially, sometimes to the point where antihypertensive drugs can be reduced or stopped.
Long-Term Management and Prognosis
Once started on antihypertensive therapy, most cats require lifelong treatment and regular monitoring. Blood pressure checks every one to three months are typical during the initial stabilisation period, with checks every three to six months once readings are consistently within a safe range.
Dietary sodium restriction is sometimes recommended, though the evidence base in cats is less robust than in dogs or humans. More important is ensuring the cat continues eating well — appetite and weight maintenance matter significantly in senior cats regardless of their blood pressure status.
Prognosis depends heavily on how much target organ damage has occurred before treatment begins and how well the underlying condition can be controlled. Cats whose hypertension is caught incidentally during routine screening generally fare far better than those presenting in hypertensive crisis. This is the strongest argument for routinely checking blood pressure in every cat from middle age onward, even when they appear outwardly well.