CONDITION
Systemic Hypertension in Cats
Systemic hypertension describes sustained high pressure within the blood vessels that circulate throughout the body. In cats, this is most often a consequence of other conditions, particularly chronic kidney disease and hyperthyroidism, rather than a standalone problem. The elevation in pressure can be present for months without producing visible changes, or it can lead to sudden signs when delicate structures, especially in the eyes or brain, are affected. Many owners first become aware of the possibility when a cat's eyes change abruptly, with pupils that stay wide, blood visible inside the eye, or sudden blindness, or when routine blood tests prompt a blood pressure check. Some cats show no outward signs at all, and raised pressure is identified only during monitoring for another condition. This page explores what elevated blood pressure looks like in practice, how it is measured and interpreted, the organs most often affected, and the ways it can be managed alongside the conditions that tend to drive it.
Why this matters now
Systemic hypertension typically develops in older cats, often in association with other conditions. It may be present for some time before obvious signs appear, as cats do not typically show symptoms until target organ damage has occurred. Blood pressure monitoring can identify hypertension before complications develop. International feline guidelines suggest measurement at least every 12 months in healthy cats aged 7 to 10 years, every 6 to 12 months from 11 years, and every 3 to 6 months in cats with kidney disease, hyperthyroidism or other risk factors.
Untreated hypertension can lead to progressive damage to vulnerable organs, particularly the eyes, kidneys, and heart. The damage may accumulate gradually, as thickening of the heart muscle and possibly worsening kidney function, or appear suddenly, as blindness from retinal detachment or as seizures and disorientation. The risk rises with pressure: a systolic reading of 160 to 179 mmHg carries a moderate risk of this damage, and 180 mmHg or above a high risk. Once the retina has detached, sight returns in only a minority of cats, whereas eye changes found before vision is affected respond to treatment much more readily.
Signals & patterns
Early signals
Changes in behaviour or activity level
Some cats become more restless, vocalise more or seem withdrawn, though these changes are nonspecific, and many hypertensive cats show no outward sign at all until an organ is damaged.
Later signals
Sudden blindness
Vision can be lost suddenly when the retina detaches or bleeds under very high pressure. Owners often notice pupils that stay wide in bright light, bumping into furniture, or hesitation before jumping.
Visible bleeding in the eyes
Blood inside the eye can be visible as a red or dark tinge behind the clear surface, and bleeding within the retina is seen during examination. Both indicate that pressure is actively damaging blood vessels.
Neurological signs
Seizures, disorientation, dullness, wobbliness, head tilt or flickering eye movements can reflect hypertensive damage to the brain, reported in between 15% and 46% of hypertensive cats. Together with sudden blindness, these signs mark the form of the disease in which feline guidelines describe lowering blood pressure in hospital over a matter of hours, with close monitoring, rather than over weeks.
Wide pupils or a change in how the eyes reflect light
Pupils that stay wide in bright light, or eyes that look unusually reflective, usually mean that the retina has already detached or bled, and sight may already be affected before the cat is seen bumping into things. This is a sign of established eye damage rather than an early sign of raised pressure; it also appears under sudden blindness above.
New disorientation in an older cat
Episodes of confusion about surroundings cannot be put down to ageing without a blood pressure reading. Where high blood pressure is the cause, pressure is already affecting the brain, so this is not an early sign of raised pressure; it also appears among the neurological signs above.
Click to read about the biological mechanisms
How this is usually investigated
Blood pressure measurement in cats requires technique adapted to their temperament. Underlying conditions that commonly cause secondary hypertension are often evaluated concurrently.
Blood pressure measurement
Fundic examination
Blood chemistry and thyroid testing
Urinalysis
Options & trade-offs
Management focuses on reducing blood pressure to protect target organs, while addressing any underlying conditions contributing to hypertension.
Anti-hypertensive medication
Medications that lower blood pressure through various mechanisms.
Trade-offs: May require dose adjustments and regular monitoring to find effective levels.
Treatment of underlying conditions
Managing hyperthyroidism or kidney disease may help control secondary hypertension.
Trade-offs: Addressing the root cause can be beneficial but may not fully resolve hypertension.
Regular monitoring
Ongoing blood pressure checks to assess treatment response and detect changes.
Trade-offs: Requires periodic visits but guides dose adjustments and shows whether target organs are being protected.
Reducing stress around blood pressure checks
Calm handling and a quiet room during measurement, so that readings reflect the cat's usual pressure rather than a stress response.
Trade-offs: Improves the accuracy of readings; it does not treat sustained high blood pressure.
Common misconceptions
"Cats show obvious signs of high blood pressure"
Many hypertensive cats appear normal until target organ damage occurs, making routine screening valuable in at-risk cats.
"Blindness from hypertension is always permanent"
Some vision can return if blood pressure is brought down quickly, but this happens in only a minority of cats with retinal detachment. Eye changes found before sight is affected respond to treatment much more readily.
"Blood pressure medication has severe side effects"
Most cats tolerate anti-hypertensive medications well, though monitoring helps detect any issues early.
Related conditions
Chronic Kidney Disease in Cats
Chronic kidney disease is one of the two most common underlying causes of systemic hypertension in cats. The kidneys play a central role in regulating blood pressure, and kidney disease often raises it through changes in fluid balance, hormone production and vessel tone, although whether pressure rises, and how high, does not appear to follow how advanced the kidney disease is.
Hyperthyroidism in Cats
Hyperthyroidism is the other major condition that drives systemic hypertension in cats. Excess thyroid hormone increases heart rate and the force of contraction, and alters blood vessel behaviour, which can elevate pressure throughout the circulation.
Hypertrophic Cardiomyopathy in Cats
Sustained high blood pressure can thicken the heart muscle in a pattern that may be indistinguishable from hypertrophic cardiomyopathy on echocardiography, so the two can be confused. High blood pressure also increases the workload on the heart, and some cats have both conditions independently, which makes it difficult to tell which came first.
Uveitis
Uveitis can develop as a consequence of systemic hypertension when elevated pressure damages blood vessels inside the eye, causing bleeding or leakage into the uveal tissues. This inflammation may appear alongside or shortly after other ocular signs such as retinal detachment or visible blood in the eye.
Diabetes Mellitus in Cats
Diabetes mellitus and systemic hypertension can occur in the same cat, most often when a diabetic cat also develops chronic kidney disease; the evidence that diabetes itself raises blood pressure in cats is limited.
Hyperaldosteronism in Cats
Primary hyperaldosteronism, in which the adrenal glands overproduce aldosterone, is a recognised cause of systemic hypertension in cats, with high blood pressure reported in 50% to 100% of affected cats in a veterinary consensus statement.
The page on this condition is being checked again and is offline for now.
Retinal Detachment
Exudative retinal detachment is the most commonly observed eye lesion in hypertensive cats and a cause of sudden blindness.
Hyphaema
High blood pressure damages blood vessels inside the eye and is a recognised cause of bleeding into the front chamber in older cats; visible blood in the eye can be the first sign an owner notices.
High blood pressure cannot be detected by looking at or handling a cat, and the signs that do appear are usually signs of damage already under way. Sudden blindness, pupils that stay wide in bright light, blood visible inside the eye, or new seizures, disorientation or unsteadiness in an older cat are presentations in which feline guidelines describe starting to bring blood pressure down within hours under monitoring, and in which sight, once lost, returns in only a minority of cats. For cats with chronic kidney disease, or with hyperthyroidism whether or not it has been treated, repeated measurement is how the quieter form is found. Understanding what blood pressure monitoring involves, including several calm readings to allow for the effect of stress, may help reduce any concerns about the process.
Last reviewed: 9 October 2026 · Dr Alastair Greenway MRCVS