Hypertension

Quick Summary: High blood pressure (hypertension) affects at least one in three cats with chronic kidney disease, and possibly as many as two in three. Damaged kidneys lose their ability to regulate blood pressure, which then rises and causes further damage to the kidneys, eyes, brain and heart. Treatment with amlodipine is usually straightforward, effective and can even reverse blindness if started quickly enough. Every cat with CKD should have its blood pressure checked regularly, regardless of disease stage.

Hypertension simply means the pressure inside the arteries is too high. The heart has to work harder to push blood through constricted vessels, and over time those vessels suffer damage. Because one of the kidney’s jobs is to help regulate blood pressure, cats whose kidneys are already compromised by CKD are particularly vulnerable.

The relationship runs in both directions. Damaged kidneys cause blood pressure to rise, and high blood pressure in turn damages the kidneys further, accelerating the progression of CKD. Treating hypertension is therefore not just about protecting the heart and eyes; it is one of the most important steps you can take to slow your cat’s kidney decline.

In cats, only systolic blood pressure (the pressure when the heart beats) is routinely measured. A reading is expressed as a single number in millimetres of mercury (mmHg).

Studies suggest hypertension is present in at least one third of cats with CKD at the time of diagnosis, and that the proportion rises as kidney disease progresses. Some studies have found rates as high as 65 percent. Age increases the risk independently of CKD, as do elevated kidney values. Cats with hyperthyroidism alongside CKD face particularly high risk, with one study finding that 87 percent of hyperthyroid cats also had hypertension.

Cats receiving erythropoiesis-stimulating agents (ESAs) for anaemia, or corticosteroids, should also be monitored closely, as both can raise blood pressure.

The renin-angiotensin-aldosterone system (RAAS) plays a central role in blood pressure regulation. When blood flow to the kidneys drops, the kidneys release hormones that cause blood vessels throughout the body to constrict, raising blood pressure as a compensatory response. In cats with CKD, this system can become chronically overactivated, contributing to sustained hypertension.

Understanding the RAAS matters because some blood pressure medications specifically target this pathway, while others work differently. The interaction between treatments and the RAAS is one reason that cats on certain medications need careful monitoring.

 

The treatment goal for CKD cats is systolic blood pressure below 160 mmHg, with an ideal target below 150 mmHg. Pushing below 120 mmHg should be avoided, as low blood pressure can reduce blood flow to already-damaged kidneys and worsen their function.

Hypertension is often called the silent killer because most cats show no obvious signs until serious damage has occurred. The symptoms below are worth knowing, but the only reliable way to detect hypertension is to measure blood pressure.

Emergency Symptoms (Act Immediately)

These indicate target organ damage and require same-day or emergency veterinary attention.

Sudden blindness. Hypertension can cause the retinas to detach, resulting in sudden vision loss. You may notice dilated or uneven pupils, or your cat may walk into objects or stop jumping. If treatment with amlodipine is started within a few days of detachment, there is roughly a 50 percent chance of partial or full vision recovery. Even delays of several weeks have not always been fatal to vision.

Stroke. Signs include inability to walk, weakness on one side, head tilt, circling and collapse. A stroke caused by hypertension is a medical emergency. Treatment within six hours gives the best chance of recovery, but improvement can still occur with later intervention.

Seizures. These may look like classic convulsions or may be subtler, such as episodes of apparent absence or confusion. Seizures caused by hypertension are reversible with blood pressure treatment in the great majority of cases; one study found neurological signs resolved or partly resolved in 92 percent of cats.

Howling, especially at night. This is a frequently overlooked but well-documented symptom of hypertension in cats. If your CKD cat develops unexplained vocalisation, blood pressure should be checked promptly.

Neurological signs. These include head pressing, twitching, facial nerve paralysis, pacing, confusion and lethargy.

Other Symptoms Worth Investigating

These do not require emergency care but should be assessed within a few days.

• Worsening kidney values in bloodwork
• Nosebleeds
• Red or hot ears
• Blood in urine
• Loss of appetite
• Restlessness

Blood pressure is measured using a cuff placed around the cat’s tail or a foreleg, connected to either a Doppler ultrasound device or a high-definition oscillometric (HDO) monitor. Doppler equipment remains the most widely used and trusted method in conscious cats.

Several measurements are taken in a quiet room, with the first discarded, and five to seven consistent readings averaged. The cat should be allowed to settle for five to ten minutes before testing begins, and the owner should remain present if possible, as cats are less stressed with a familiar person nearby.

Because many cats show higher readings at the vet than they would at home (sometimes called situational or white-coat hypertension), home monitoring is increasingly recommended. Studies suggest vet-measured readings can be up to 28 mmHg higher than at-home readings, and around 40 percent of cats show situational hypertension to some degree. Home monitoring removes this variable and allows trends to be tracked over time.

Affordable oscillometric monitors designed for home use (such as the Contec08A-VET, available for around 60 to 75 US dollars) have been found reasonably accurate by many owners when compared against veterinary equipment.

Hypertension can exist at any stage of CKD. A normal creatinine or SDMA value is not reassurance that blood pressure is fine.

IRIS (International Renal Interest Society) guidelines include blood pressure as a substage alongside kidney function markers. Every CKD cat should be substaged for blood pressure at each reassessment, just as it is substaged for proteinuria.

Cats with CKD are presumed to have target organ damage (TOD) even when it is not clinically visible, and should be treated accordingly once blood pressure reaches 160 mmHg or above.

When to Start

Treatment should begin when systolic blood pressure is consistently 160 mmHg or above on two or more separate occasions. Cats showing clear signs of target organ damage (blindness, stroke, seizures, worsening kidneys) should be treated immediately, without waiting for multiple readings to confirm persistent hypertension.

Amlodipine: First Choice

Amlodipine is a calcium channel blocker and the preferred first-line treatment for hypertension in cats. It is effective in 60 to 100 percent of cats, typically reduces systolic blood pressure by 30 to 40 mmHg or more, takes effect within a week, and is generally safe and well tolerated. It is also the only medication with evidence for reversing blindness caused by retinal detachment.

The usual starting dose is 0.625 mg once daily. Cats over 4 kg, those with severe hypertension (above 200 mmHg), or those who do not respond adequately may be increased to 1.25 mg daily. Changes should be made gradually.

Blood pressure should be rechecked 7 to 10 days after starting or adjusting amlodipine.

Amlodipine is available generically and inexpensively. It is sometimes found in pharmacy low-cost drug programs in the United States.

Possible side effects include mild initial lethargy (usually temporary), and rarely constipation, loss of appetite, limb swelling or gingival hyperplasia (gum enlargement). Amlodipine can activate the RAAS over time, which is one reason a second medication is sometimes added.

Interactions to be aware of: maropitant (Cerenia) may enhance the effect of amlodipine; if both are used, giving them 12 hours apart is a reasonable precaution. Cimetidine (Tagamet) may also increase amlodipine’s effect; famotidine (Pepcid) is a safer alternative for stomach acid control. Cyproheptadine has calcium-channel-blocking properties and combination with amlodipine warrants caution.

Telmisartan: An Alternative or Addition

Telmisartan (Semintra) is an angiotensin receptor blocker (ARB). It was approved in the United States in 2018 for treating hypertension in cats and has also been used for several years in Europe and elsewhere to manage proteinuria.

Telmisartan is an appropriate first choice, particularly in proteinuric cats, and studies show it reduces systolic blood pressure by around 20 to 24 mmHg. This is a smaller reduction than amlodipine typically achieves, and it has not been studied in cats with blood pressure above 200 mmHg. It has not been shown to reverse blindness or assist with strokes.

Telmisartan is often used in combination with amlodipine when amlodipine alone does not adequately control blood pressure. The combination appears safe, with no clinically significant hypotension reported at recommended doses. When combined with amlodipine, the telmisartan dose is typically 1 mg/kg per day.

The standard dose as sole therapy is 2 mg/kg once daily (after an initial two-week twice-daily loading phase for hypertension).

ACE Inhibitors: Supporting Role Only

ACE inhibitors such as benazepril (Fortekor) and enalapril are sometimes prescribed for hypertension, but they are not recommended as sole antihypertensive therapy in cats. Studies consistently show they are insufficient to bring blood pressure below 170 mmHg in the majority of cats with hypertension.

ACE inhibitors are used to manage proteinuria and may be added to amlodipine to counteract RAAS activation or provide additional blood pressure reduction. When adding an ACE inhibitor to amlodipine, kidney values should be rechecked 7 to 10 days later, as a modest rise in creatinine is possible.

ACE inhibitors should not be started in a dehydrated or unstable cat, and are used with particular caution in cats with severe CKD.

Beta Blockers

Atenolol is occasionally used alongside other medications when blood pressure remains difficult to control, or when tachycardia is present. It is not effective as sole antihypertensive therapy in most cats.

Your vet may suggest reducing dietary sodium. Current IRIS guidelines note there is no strong evidence that sodium restriction helps cats with hypertension specifically, and that if it is pursued it should be gradual and in addition to medication, not instead of it. Abrupt sodium reduction can itself activate the RAAS. Palatability and your cat’s overall nutritional needs should take priority over sodium content.

Once treatment begins, blood pressure should be measured:

• 7 to 10 days after starting or adjusting medication
• Every 1 to 3 months once stable, depending on your vet’s recommendation
• Any time kidney values worsen unexpectedly
• At every CKD reassessment appointment

Potassium levels should also be monitored, as amlodipine can contribute to low potassium (hypokalemia) in some cats.

If blood pressure remains difficult to control despite appropriate doses of amlodipine, rare conditions such as hyperaldosteronism should be considered.

Cats whose hypertension is detected and treated have a substantially better outlook than those in whom it goes unmanaged. Because CKD and hypertension form a self-reinforcing cycle, bringing blood pressure under control is one of the most meaningful interventions available. Many cats on amlodipine remain stable for months to years, and some show improvement in kidney values once hypertension is resolved.

Blindness caused by retinal detachment is often partially or fully reversible with prompt treatment. Neurological symptoms caused by hypertensive encephalopathy resolve in the great majority of cats once blood pressure is brought under control.

Hypertension can be present at any IRIS stage. It should be checked at diagnosis and monitored throughout your cat’s life with CKD.

How often should my CKD cat’s blood pressure be checked? At minimum, at every CKD reassessment appointment. Most vets check blood pressure every one to three months once a cat is stable on treatment, and every three to six months in cats not yet requiring medication. If kidney values worsen unexpectedly, blood pressure should be checked regardless of when it was last measured.

My cat’s blood pressure was high at the vet but normal at home. Which reading should I trust? Home readings are generally more reliable because they are taken in a stress-free environment. A difference of up to 28 mmHg between clinic and home readings has been documented. If your cat shows signs of target organ damage despite normal clinic readings, discuss home monitoring with your vet or treat based on symptoms.

Can hypertension cause blindness? Yes. High blood pressure is one of the most common causes of sudden blindness in cats. If your cat loses vision abruptly, it should be treated as an emergency. Starting amlodipine within a few days of retinal detachment gives the best chance of vision recovery, but improvement has been documented even with delays of several weeks.

Is amlodipine safe for cats with CKD? Yes. Amlodipine is generally considered safe and is unlikely to lower blood pressure excessively. Rare side effects include lethargy in the early days, mild digestive changes and gum changes. It does not typically cause the sharp creatinine increases sometimes seen with ACE inhibitors.

What if my vet says my cat’s blood pressure is fine but it is showing neurological signs? Hypertension can spike intermittently, appearing normal during a clinic visit. If your cat is showing neurological signs or has gone blind, treatment with amlodipine is reasonable even without a confirmed elevated reading. The presence of target organ damage justifies treatment after a single measurement session under ACVIM guidelines.

Will my cat need blood pressure medication for life? In most cases, yes. Once hypertension is established in a CKD cat, the underlying cause (damaged kidneys) does not resolve. If your cat’s blood pressure is caused partly by hyperthyroidism, treating the thyroid condition may reduce or eliminate the need for blood pressure medication.

My cat’s blood pressure is 158 mmHg. Does it need treatment? Not necessarily, unless signs of target organ damage are present. Readings in the 140 to 159 mmHg range are in the prehypertension zone. Recheck in three to six months, and begin treatment if readings reach 160 mmHg or above on two occasions, or sooner if any ocular or neurological signs appear.

ACVIM consensus statement: guidelines for the identification, evaluation and management of hypertension in dogs and cats (2018). Acierno MJ et al. Journal of Veterinary Internal Medicine 32(6) pp1803-1822.

Bijsmans ES et al. (2015). Changes in systolic blood pressure over time in healthy cats and cats with chronic kidney disease. Journal of Veterinary Internal Medicine 29(3) pp855-861.

Bijsmans ES et al. (2016). Factors influencing the relationship between the dose of amlodipine required for blood pressure control and change in blood pressure in hypertensive cats. Journal of Veterinary Internal Medicine 30(5) pp1630-1636.

Brown SA & Roura X (2022). Systemic hypertension. International Renal Interest Society.

Coleman AE & Elliott J (2022). Inhibition of the renin-angiotensin-aldosterone system in cats and dogs: the emerging role of angiotensin II receptor blockers. International Renal Interest Society.

Coleman AE et al. (2019). Safety and efficacy of orally administered telmisartan for the treatment of systemic hypertension in cats. Journal of Veterinary Internal Medicine 33(2) pp478-488.

Elliott J (2025). Fibroblast growth factor 23 — a review with particular reference to the physiology and pathophysiology of phosphate homeostasis in the cat. Veterinary Journal 309.

Glaus TM et al. (2019). Efficacy of long-term oral telmisartan treatment in cats with hypertension. Journal of Veterinary Internal Medicine 33(2) pp413-422.

Huang JHC, Lourenço BN & Coleman AE (2025). The renin-angiotensin-aldosterone system in kidney diseases of cats and dogs. The Veterinary Journal 309 106287.

IRIS Treatment Recommendations for CKD in Cats (2023). International Renal Interest Society.

ISFM consensus guidelines on the diagnosis and management of hypertension in cats (2017). Taylor SS et al. Journal of Feline Medicine and Surgery 19 pp288-303.

Koo ST & Carr AP (2022). Comparison of home blood pressure and office blood pressure measurement in dogs and cats. Canadian Journal of Veterinary Research 86(3) pp203-208.

Lawson JS & Jepson RE (2021). Feline comorbidities: the intermingled relationship between chronic kidney disease and hypertension. Journal of Feline Medicine and Surgery 23(9) pp812-822.

Moretto L et al. (2023). Manifestations of hypertensive encephalopathy in cats. Journal of Feline Medicine and Surgery 25(2).

Syme HM et al. (2002). Prevalence of systolic hypertension in cats with chronic renal failure at initial evaluation. Journal of the American Veterinary Medical Association 220 pp1799-1804.

Young WM et al. (2019). Visual outcome in cats with hypertensive chorioretinopathy. Veterinary Ophthalmology 22(2) pp161-167.