A single reading of 170 mmHg in a nervous cat means very little. Feline hypertension is diagnosed above 160 mmHg only when the number repeats across several visits and there is evidence of damage to an organ that pressure can hurt. Amlodipine is prescription-only and starts at 0.625 mg per cat per day; the eye exam, not the cuff, tells you whether treatment came in time.
Why 160 mmHg, and Why One Reading Is Not Enough
The cutoffs most labs and cardiologists use are 150 mmHg as the upper end of normal, 150 to 159 as borderline, 160 to 179 as hypertension, and 180 or above as severe. The reason for the gap between 150 and 160 is measurement noise: a cat that hates the clinic can read 20 to 40 mmHg high, and a cat that purrs through the cuff can read falsely low.
So the rule is repetition. Take 5 to 7 readings in one sitting, throw out the first, and average the rest. Confirm on at least 3 separate visits 1 to 2 weeks apart, or on 2 visits plus home or 24-hour ambulatory readings. Doppler and oscillometric devices disagree by 5 to 15 mmHg, so stay with one device and one clinic for the trend.
The Four Organs You Are Actually Protecting
Eyes: retinal hemorrhage, detachment and sudden blindness. Kidneys: protein in urine and a rising creatinine, though kidney disease also causes hypertension, which makes the direction hard to prove. Heart: a thickened left ventricle and a murmur. Brain: seizures, disorientation, sudden wobbly gait. A cat with a systolic of 180 mmHg and a normal fundic exam still needs treatment, but a cat at 165 mmHg with a clean eye exam, clean urine and a normal echo may be watched for 2 to 4 weeks first.
Reading the Numbers
| Systolic (mmHg) | Meaning | Next step | Recheck |
|---|---|---|---|
| Below 150 | Normal | Routine screening yearly after age 7 | 12 months |
| 150 to 159 | Borderline | Repeat, check urine protein and eyes | 2 to 4 weeks |
| 160 to 179 | Hypertensive | Start amlodipine, target organ panel | 7 to 14 days |
| 180 and above | Severe | Treat today, eye exam same week | 3 to 7 days |
Amlodipine: 0.625 mg per Cat, Then Titrate
The starting dose is 0.625 mg per cat once daily, which is one quarter of a 2.5 mg tablet, regardless of whether the cat weighs 3 kg or 6 kg. A 0.625 mg tablet exists in some markets, which beats splitting a scored quarter by hand. Recheck systolic pressure 7 to 14 days later. If it is still above 160 mmHg, most vets raise to 1.25 mg daily, then to 1.875 mg, with a practical ceiling around 2.5 mg per cat per day. Weight-based dosing at 0.2 mg/kg lands in the same place for a 4 kg cat and is used by some internists.
The failure mode is not the drug, it is the tablet. A quarter of a 2.5 mg tablet crumbles, owners under-dose for weeks, and the recheck shows no change. Ask for the 0.625 mg size, or have the pharmacy compound a liquid. Do not add a second drug before confirming the cat actually swallows the first.
Eyes: Blindness Is Sometimes Reversible
Hypertensive retinopathy is the most treatable cause of sudden blindness in an older cat. If the retina is detached but the vessels are intact, vision can return in 1 to 3 weeks once pressure drops below 160 mmHg, and some cats recover in 5 to 10 days. If the retina has been detached for weeks, or there is a large hemorrhage, the change is usually permanent. That asymmetry is the argument for an eye exam within 48 hours of a high reading, not next month.
When the Kidney Is the Cause
Roughly 2 in 3 cats with hypertension also carry chronic kidney disease (CKD), and the direction of cause is often unclear: pressure damages the kidney, and a failing kidney raises pressure through renin and sodium retention. The practical consequences are simple. Measure pressure in every cat with a creatinine above 2.0 mg/dL or an SDMA above 18, and check urine protein in every cat started on amlodipine. Expect a creatinine rise of 0.3 mg/dL or more in the first 30 days; a small rise with stable pressure is normal, while a large rise with lethargy means the dose needs review, not that the drug was wrong.
The First 30 Days
- Day 0: 5 to 7 readings, fundic exam, urine protein:creatinine, chemistry with SDMA, thyroid T4.
- Day 7 to 14: repeat pressure; expect a fall of 20 to 40 mmHg, not to normal on day 3.
- Day 14: check for lethargy or inappetence, the common early amlodipine side effects.
- Day 30: repeat chemistry, since a creatinine rise of 0.3 mg/dL or more means the kidney was depending on high pressure.
- Month 3 onward: pressure and chemistry every 3 to 6 months, plus a blood pressure check before any anesthesia.
What Owners Get Wrong
Two habits cost cats their sight. The first is treating a single high reading, which produces a cat on amlodipine for years with normal pressure and no diagnosis. The second is skipping the eye exam because the cat seems fine, which is how a detached retina is found at week 6 instead of week 1. A cat over 10 years old should have pressure measured at every annual visit, the same way a dog gets its teeth checked. Pair this with the socialization checklist idea of low-stress handling, since a calm cat gives a truer number, and with the meeting room checklist if you are about to bring a second cat into a household with a hypertensive senior. The cat age tool converts years to a human equivalent and makes the case for starting screening at 7.
Frequently asked
My cat read 175 mmHg once at the vet. Does it need medication?
Not from one reading. Clinic stress alone can push a cat 20 to 40 mmHg high, so the number has to repeat on 2 or 3 visits 1 to 2 weeks apart, or be confirmed with home or 24-hour ambulatory measurement. Treatment usually starts when pressure stays above 160 mmHg and there is target organ evidence, such as retinal changes, protein in the urine, or a thickened left ventricle. A calm cat, the same device, and the same clinic make the trend readable.
What is the amlodipine dose for a cat?
The standard start is 0.625 mg per cat once daily, which is a quarter of a 2.5 mg tablet and does not scale with body weight. Pressure is rechecked in 7 to 14 days, and most vets step up to 1.25 mg and then 1.875 mg if the reading stays above 160 mmHg, with a practical ceiling near 2.5 mg per cat per day. Amlodipine is prescription-only, so the dose and the steps are your vet's call.
The cat went blind. Can vision come back?
Sometimes, and the timing decides it. If the retina is detached but the vessels are intact and pressure falls below 160 mmHg quickly, vision can return within 1 to 3 weeks, and a few cats improve in 5 to 10 days. If detachment has lasted weeks or there is heavy hemorrhage, the loss is usually permanent. That is why an eye exam within 48 hours of a high reading matters more than a repeat pressure check next month.