Cats do not show high blood pressure the way people do. There is no headache to report and no nosebleed that anyone connects to it. What gets a cat diagnosed is a clinic that measures pressure routinely, plus an owner who notices the cat walking with its head low and bumping into doorframes.
Sudden blindness, a pupil that stays wide in bright light, a seizure, or bleeding from the nose means same-day assessment. Retinal detachment from pressure above roughly 180 mmHg can sometimes be reversed if treated within 24 to 72 hours, and rarely after that.
When it counts as an emergency
Go now if the cat is suddenly bumping into furniture, if the pupils are wide and do not narrow when you shine a light, if the eyes look cloudy or filled with blood, if there is a seizure, or if a nosebleed lasts more than a few minutes. Acute blindness in an older cat is the single most common way hypertension is found. Add lethargy, confusion, walking in circles or pressing the head into a wall and the brain is involved, which carries a much worse prognosis.
Why it is so easy to miss
Between 6 and 10 percent of cats over 10 have hypertension, and almost all of them have a second disease driving it. Chronic kidney disease and hyperthyroidism account for the majority; hyperaldosteronism, diabetes and obesity are smaller contributors. The pressure itself causes no pain and no behaviour change until a target organ gives way, so a cat can sit at 200 mmHg for months looking normal. The first sign is often the owner reporting that the cat no longer jumps onto the bed, which gets filed as arthritis.
Who should be measured
Any cat over 10 at every annual visit, and any cat with kidney disease or an untreated thyroid at every 3 to 6 months. Also measure in cats with a heart murmur, protein in the urine, sudden blindness, or unexplained weight loss. Breeds are not exempt: the same rules apply to a 4 kg domestic shorthair and a 7 kg Maine Coon. Ask for the number in writing, because a note that says “BP normal” tells you nothing at the next visit.
How to get a number you can trust
Doppler is the reference method in cats; oscillometric machines are convenient but read higher and are less reliable at the low end. Pressure is taken with the cat calm, in a quiet room, cuff about 40 percent of the circumference of the limb or tail, and 5 to 7 readings are collected with the first 1 or 2 discarded. The median of the rest is the result. A single high reading in an anxious cat proves nothing: white-coat effect alone can add 20 mmHg.
The thresholds most vets work to: under 150 is normal, 150 to 160 is borderline and gets a recheck, 160 to 180 needs confirmation over 2 to 4 visits and a search for organ damage, above 180 with any organ damage means treatment starts today. A cat consistently over 180 without damage still usually gets treated.
What high pressure damages
The eye is the most sensitive target: retinal hemorrhage, then detachment, then irreversible blindness within days. The kidney loses protein and declines faster, which is why every hypertensive cat gets a urine protein to creatinine ratio. The heart thickens its left ventricle and may develop a murmur or arrhythmia. The brain produces seizures, ataxia and personality change. All four are silent until they are not, which is the whole argument for measuring pressure rather than waiting for a symptom.
Amlodipine and the starting dose
Amlodipine is first-line: 0.625 mg once daily for a cat under about 5 kg, 1.25 mg once daily for a larger cat, given at the same time each day. Recheck pressure in 7 to 14 days, and if it is still above 160, increase by 0.625 mg steps every 2 weeks up to a usual maximum of 2.5 mg daily. Most cats respond within a few days, and the drug is generally well tolerated. Do not split a 5 mg human tablet by eye — the difference between 0.6 and 1.2 mg matters, and a compounding pharmacy gets it exact.
If protein in the urine is significant, telmisartan at 1 to 2 mg per kg daily is often added or used instead, because it lowers pressure and reduces protein loss. ACE inhibitors are weaker at lowering pressure in cats and are not a substitute for amlodipine.
What to monitor, and when
Recheck blood pressure at 7 to 14 days after any change, then every 3 months once stable. Check creatinine, SDMA and potassium at baseline, at 2 weeks, and every 3 to 6 months. Amlodipine can drop pressure too far and cause lethargy, weakness or a refusal to eat — a cat that becomes quiet on treatment needs a pressure check, not a dose increase. If the cat also has kidney disease, expect the creatinine to rise slightly as pressure falls; that is acceptable, a crashing cat is not.
Reading the numbers
| Systolic value | What it means | Next step |
|---|---|---|
| Under 150 | Normal | Recheck in 6 to 12 months |
| 150 to 160 | Borderline | Repeat in 2 to 4 weeks |
| 160 to 180, no damage | Hypertension | Confirm, then treat |
| Above 180 with damage | Severe | Treat today, recheck in 7 days |
| Above 200 | Crisis risk | Treat now, eye exam same day |
Five steps for this month
- If the cat is over 10, book a blood pressure reading with the annual bloodwork, and ask for the number.
- Have the eyes examined with a fundoscope at the same visit; the retina shows damage before the cat goes blind.
- Run a urine protein to creatinine ratio at baseline.
- If amlodipine is started, set a reminder for day 10 and recheck.
- Watch for the quiet-cat sign after any dose change and call rather than wait for the next appointment.
Most hypertensive cats are kidney cats first, so the staging in kidney disease early signs is the other half of the picture. Older cats need a different baseline for everything from weight to hydration, covered in senior cat care. If the pressure spike brings a seizure, treat it as a seizure emergency first and investigate after.
Frequently asked
My cat went blind overnight. Can the sight come back?
Sometimes, if the cause is a retinal detachment from high pressure and treatment starts within 24 to 72 hours. Amlodipine lowers the pressure and some retinas reattach over days to weeks, but recovery is partial in most cats and permanent blindness is common. This is why an acute blindness in an older cat is treated as an emergency rather than an eye problem to check next week.
The vet got 175 on one reading. Does my cat need medication?
Not from a single reading. White-coat stress alone can add 20 mmHg, so the standard is 5 to 7 readings with the first one or two discarded, taking the median. A value of 160 to 180 is usually confirmed over 2 to 4 visits along with a search for organ damage, and treatment starts when it holds above 160 with damage or above 180 without.
Can I control this with diet instead of amlodipine?
Diet helps the underlying disease, not the pressure itself. A renal diet slows kidney progression and low sodium is sensible, but no diet reliably brings 190 mmHg down to 150. Amlodipine at 0.625 mg daily is cheap, well tolerated and effective within days, so it is the standard first step alongside treating the kidney or thyroid problem that caused the hypertension.