Senior Cat Normal Lab Values & Vital Signs
Reference ranges for senior cat bloodwork (BUN, creatinine, SDMA, phosphorus, T4) and vital signs (temperature, heart rate, respiratory rate, blood pressure).
Quick answer: For most senior cats, normal values are roughly BUN 16 to 36 mg/dL, creatinine 0.8 to 2.4 mg/dL, SDMA 14 ug/dL or less, phosphorus 3.1 to 7.5 mg/dL, and total T4 0.8 to 4.0 ug/dL. Normal vital signs are temperature 100.5 to 102.5 F, heart rate 140 to 220 bpm, and a resting respiratory rate under 30 breaths per minute.
These are general reference ranges to help you understand a senior cat's lab report and home vitals. Ranges vary by laboratory and equipment, and a single value outside the range is not always a problem. Always interpret results with your veterinarian, who looks at trends over time and the full picture, not one number alone.
Senior Cat Bloodwork Reference Ranges
| Test | Typical Normal Range | What It Reflects |
|---|---|---|
| BUN (blood urea nitrogen) | 16 to 36 mg/dL | Kidney function and hydration |
| Creatinine | 0.8 to 2.4 mg/dL | Kidney filtration |
| SDMA | 0 to 14 ug/dL | Early kidney marker, rises before creatinine |
| Phosphorus | 3.1 to 7.5 mg/dL | Kidney health and mineral balance |
| ALT (liver enzyme) | 20 to 100 U/L | Liver cell health |
| Glucose | 70 to 150 mg/dL | Blood sugar (stress can raise it in cats) |
| Total T4 (thyroid) | 0.8 to 4.0 ug/dL | Thyroid hormone, screens for hyperthyroidism |
| USG (urine specific gravity) | 1.035 to 1.060 | Urine concentration, kidney ability |
| PCV (packed cell volume) | 30 to 45 percent | Red blood cell level, screens for anemia |
These ranges reflect values commonly published by veterinary diagnostic laboratories and referenced in AAFP and IRIS (International Renal Interest Society) guidance. In senior cats, trends matter as much as single values. A creatinine climbing within the normal range across visits, paired with dilute urine, can point to early chronic kidney disease. A rising T4 supports a diagnosis of hyperthyroidism, and a persistently high glucose with weight changes can indicate diabetes.
Senior Cat Vital Signs
| Vital Sign | Normal Range | Notes |
|---|---|---|
| Body temperature | 100.5 to 102.5 F (38.1 to 39.2 C) | Below 100 F or above 103.5 F needs a vet |
| Heart rate | 140 to 220 bpm | Lower at home when relaxed, often 120 to 180 |
| Resting respiratory rate | Under 30 breaths per minute | Count while sleeping or resting calmly |
| Blood pressure (systolic) | Under 140 mmHg | 160 mmHg and above suggests hypertension |
| Body weight | About 8 to 12 lb (3.6 to 5.4 kg) | Varies by breed; ideal body condition is 5 of 9 |
The resting respiratory rate is the single most useful number you can track at home. Count the breaths (one rise and fall of the chest) for 30 seconds and double it while your cat sleeps. A calm resting rate under 30 is reassuring. A sustained rate above 30, or labored effort, can be an early sign of heart or lung disease and is reason for a same-day vet call. Sudden high blood pressure links closely to feline hypertension, which often accompanies kidney and thyroid disease.
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How to Use These Numbers
Keep a copy of your cat's lab reports and note the trend, not just the latest value. Ask your vet for the actual numbers at each senior visit so you can watch kidney, thyroid, and glucose markers over time. To see where your cat sits by age, check the cat years to human years chart, and plan portions with the senior cat food calculator.
This page is educational and complements, but does not replace, your veterinarian. Always discuss your cat's specific results with a professional who knows their history.
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Frequently Asked Questions
What are normal kidney values for a senior cat?
Common reference ranges are BUN about 16 to 36 mg/dL, creatinine about 0.8 to 2.4 mg/dL, SDMA at or below 14 ug/dL, and phosphorus about 3.1 to 7.5 mg/dL. Values trending up across visits, or urine that is no longer concentrated, can signal early kidney disease even when each number still looks borderline normal.
What is a normal resting respiratory rate for a cat?
A healthy cat at rest or asleep breathes fewer than 30 breaths per minute, often 16 to 30. Count the rise and fall of the chest for 30 seconds and double it while your cat is calm. A sustained resting rate above 30, or visible effort, can indicate heart or lung disease and warrants a same-day vet call.
What is a normal body temperature for a cat?
Normal feline body temperature is about 100.5 to 102.5 F (38.1 to 39.2 C). Below 100 F or above 103.5 F is abnormal and needs veterinary attention. A digital pet thermometer used rectally gives the most accurate reading. Ear thermometers are easier but less precise, so use them only as a rough guide.
What is a normal heart rate for a senior cat?
A cat heart rate is typically 140 to 220 beats per minute, often higher at the clinic due to stress. At home and relaxed, many cats settle to 120 to 180. Persistently high rates, very low rates, or an irregular rhythm should be checked, since heart disease and hyperthyroidism are common in older cats.
What blood pressure is too high for a cat?
A systolic blood pressure under about 140 mmHg is considered normal. Readings of 160 mmHg and above suggest hypertension and risk to the eyes, kidneys, heart, and brain. Hypertension is common alongside kidney disease and hyperthyroidism, so vets often check blood pressure as part of senior screening.
Why does my senior cat need a T4 thyroid test?
Total T4 measures thyroid hormone, with a typical range of about 0.8 to 4.0 ug/dL. Hyperthyroidism, an overactive thyroid, is one of the most common diseases in cats over 10 and raises T4. It causes weight loss despite a good appetite, increased thirst, and a fast heart rate, so T4 is a key senior screening value.
Are these lab ranges the same at every clinic?
No. Reference ranges vary by laboratory, equipment, and the units used, and a single result outside the range is not always a problem. Always interpret values with your veterinarian, who considers your cat trends over time, symptoms, and the full panel together rather than any one number in isolation.
How often should a senior cat have bloodwork?
Most vets recommend bloodwork, urine testing, and blood pressure at least once a year from age 7 to 10, and twice a year from about 11 onward or sooner if a cat has a chronic condition. Regular testing builds a baseline so subtle trends, the earliest sign of kidney or thyroid disease, are easy to spot.
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