From about age 7 a cat's body hides problems well, and the physical exam stops being enough. The schedule most vets use is one full panel a year from 7, and every 6 months from 10, because that is how often kidney disease, hyperthyroidism, and diabetes become detectable in blood before the cat looks sick. A senior panel is not a vague full checkup: it is a defined set of tests, each answering a specific question.
The schedule: why 7 and why 10
Cats are senior at 7 and geriatric at 10 to 12. Kidney function, thyroid output, and glucose tolerance all drift in that window, while the cat compensates so smoothly that owners notice nothing until 60 to 75 percent of kidney function is gone. A 6-month gap catches drift that a 12-month gap hides. Add a visit any time weight changes by more than 5 percent.
Complete blood count: anemia, infection, platelets
The CBC answers three questions at once. Red cell count and hematocrit show anemia, which in an older cat usually points to chronic kidney disease, blood loss from an ulcer or tumor, or immune-mediated destruction. White cells separate bacterial infection from inflammation and stress. Platelets flag bleeding risk before a dental extraction. Two patterns matter: a mildly anemic cat with high BUN and creatinine is a kidney cat until proven otherwise, and a high white count with a fever that will not clear on 5 to 7 days of antibiotics needs imaging, not a second antibiotic.
Chemistry panel: liver, kidney, glucose, electrolytes
Most diagnoses come out of the biochemistry panel. It reports BUN and creatinine for filtration, ALT and ALKP for liver injury and bile flow, glucose, total protein and albumin, calcium, phosphorus, potassium, and often pancreatic lipase. In cats ALT is the more liver-specific enzyme; ALKP can rise from liver, bone, or simply from 2 days of not eating.
Phosphorus deserves its own line: it climbs as filtration falls, and controlling it with a renal diet is one of the few interventions with a clear effect on comfort and survival time. Potassium falls in many kidney cats and in hyperthyroid cats after treatment, producing hind-leg weakness owners describe as "suddenly wobbly".
SDMA versus creatinine
Creatinine is a muscle byproduct cleared by the kidney, and it rises only after roughly 75 percent of function is lost. It also tracks muscle mass, so a thin old cat can look better than it is. SDMA rises at about 40 percent loss, so it flags kidney disease 1 to 4 years earlier, and muscle wasting does not pull it down.
An SDMA of 18 or above with normal creatinine is early kidney disease. The response is not a drug but a recheck in 2 to 4 weeks with a urinalysis and blood pressure, then a renal diet. High SDMA with concentrated urine is worth repeating before acting.
T4, and the thyroid-kidney see-saw
Total T4 belongs in every panel for a cat over 8, because early hyperthyroidism hides inside the reference range. Values fluctuate, so a borderline high T4 in a cat losing weight on a good appetite justifies free T4 by dialysis or a recheck in 2 to 4 weeks.
The reverse trap matters more. Thyroid hormone inflates kidney filtration, so roughly 3 in 10 hyperthyroid cats have kidney disease masked by it. Treating the thyroid drops filtration to its real level and creatinine climbs within 2 to 4 weeks. That is unmasking, not drug damage, and it is why creatinine, SDMA, and urine specific gravity are measured before treatment starts.
Urinalysis: concentration and protein
Specific gravity shows whether the kidney can still concentrate. Above 1.035 is a well-concentrated cat and 1.030 to 1.035 is adequate, but a persistent 1.012 to 1.025 in a cat that is not drinking heavily or on fluids is a warning even with normal creatinine.
The urine protein-to-creatinine ratio (UPC) quantifies protein loss: under 0.2 is normal, 0.2 to 0.4 borderline, above 0.4 proteinuria that usually calls for an ACE inhibitor or telmisartan. A culture belongs here too, since about 1 in 5 kidney cats has a urinary infection without typical signs.
Blood pressure and imaging
Systolic pressure is taken with a cuff, ideally 3 to 5 readings averaged. Under 150 mmHg is normal, 150 to 159 borderline, and 160 or above is hypertension that damages kidneys, heart, and retina. Retinal detachment can blind a cat within days, so a suddenly dilated pupil or bumping into furniture is an emergency.
Imaging is targeted. Chest X-rays for a cough, abdominal ultrasound when the chemistry suggests pancreatic or biliary disease, and echocardiography for a murmur or before anesthesia. A murmur at 12 is common and often benign, but an echo before a dental tells you whether the cat can be safely anesthetized.
How to read an IRIS stage
The International Renal Interest Society stages on fasting creatinine, with SDMA as support, and it is the language vets use to compare visits.
| Stage | Creatinine (mg/dL) | What it means |
|---|---|---|
| 1 | below 1.6 | No azotemia; SDMA 18 or higher or poor concentration is the clue |
| 2 | 1.6 to 2.8 | Mild azotemia; most cats still eat normally |
| 3 | 2.9 to 5.0 | Moderate; appetite, weight, and phosphorus need management |
| 4 | above 5.0 | Severe; uremic signs, needs close monitoring |
Stage is not the whole picture. IRIS substages by UPC and by blood pressure, because a stage 2 cat with heavy proteinuria and high pressure declines faster than a stage 3 cat with neither. Cats are staged on at least 2 fasting, well-hydrated samples, never one number from a stressful visit.
Five things to do before the appointment
- Write down what the cat eats in 3 days, treats included.
- Measure 24-hour water intake; above 45 ml per kg per day is polydipsia.
- Weigh the cat at home, or ask for a scale weight every visit and keep the list.
- Ask for a fasting sample and for blood pressure before any stressful procedure.
- Keep results in one folder and compare trends. Daily care for this age is in senior cat care, and owner-visible signs are in kidney disease early signs.
None of this replaces an exam, but it sharpens one: a vet who knows the cat lost 400 g in 6 months and SDMA went from 12 to 22 orders the right next test instead of guessing. The rest of the screening map is on the health section index.
Frequently asked
Is a yearly blood panel really necessary for an indoor cat?
From age 7 it is the cheapest way to catch kidney disease, hyperthyroidism, and diabetes while they are still manageable. Cats hide illness until 60 to 75 percent of kidney function is gone, and a physical exam cannot detect a rising SDMA or a borderline T4. One panel a year from 7 and every 6 months from 10 is the usual compromise between cost and early detection.
My cat's SDMA is high but creatinine is normal. What now?
That combination usually means early kidney disease, since SDMA rises at roughly 40 percent function loss while creatinine waits for about 75 percent. The usual response is not medication but a recheck in 2 to 4 weeks with a urinalysis and blood pressure, then a renal diet if the trend holds. Repeat before acting if the urine is well concentrated.
Why measure blood pressure at a senior checkup?
Hypertension is common in older cats and damages the kidneys, heart, and retina without obvious signs. Retinal detachment can blind a cat within days, and a systolic reading of 160 mmHg or higher usually needs treatment. Measuring it takes a few minutes with a cuff and is far easier than managing sudden blindness later.