Urine tells you what the blood cannot: whether the kidney can still concentrate, whether the pH favors one crystal over another, whether protein is leaking, and what is living in the sediment. The 4 numbers that carry most of the information are a specific gravity of 1.035 or higher, a pH between 6.0 and 6.5, a protein-to-creatinine ratio under 0.2, and a sediment with fewer than 5 white cells per high-power field. Everything else on the strip is context for those 4.
Collect it properly or the numbers lie
A sample that sat in a litter box for an hour, or in a fridge for a day, has already changed. Cells lyse, casts dissolve, crystals precipitate, and bacteria multiply. Aim for 5 to 10 mL, read the strip within 30 minutes, and refrigerate at 2 to 6 °C for no more than 6 hours if the lab is off site; bring it back to room temperature before reading specific gravity. Cystocentesis gives the cleanest sample and is the only acceptable one for culture. A free-catch sample is fine for specific gravity and chemistry but a few bacteria in it mean nothing, while the same few bacteria in a cystocentesis sample mean a urinary tract infection.
Specific gravity: 1.035 is the line
Feline urine ranges from roughly 1.001 to 1.065, and the middle of that range is where the useful distinctions sit. A value of 1.035 or higher says the kidney still concentrates well. Between 1.013 and 1.034 the urine is poorly concentrated; between 1.008 and 1.012 it is isosthenemic, meaning it matches the kidney's own filtrate; below 1.008 it is dilute. Read specific gravity with a refractometer, not with the reagent strip, which reads protein and pH rather than density and is unreliable in cats. The clinical payoff is in pairs: an azotemic cat with a specific gravity of 1.040 or higher is likely prerenal or dehydrated, while an azotemic cat sitting at 1.020 is losing concentrating ability.
pH: the 6.0 to 6.5 band
Cats on a meat-based diet usually run 6.0 to 6.5, with a normal spread of 5.5 to 7.0. Below 6.0 the urine favors calcium oxalate crystals, which form in acidic urine and are the commonest feline urolith in many regions. Above 6.6 to 7.0 struvite (magnesium ammonium phosphate) becomes insoluble. The number is also the least stable item on the strip: a sample left at room temperature for 2 to 4 hours drifts upward as bacteria split urea, and a cat eating within 3 hours of collection can read 0.3 to 0.6 units higher than its baseline. Measure pH on fresh urine only, and treat one reading as a snapshot rather than a diagnosis.
Protein: the strip overstates, the ratio decides
The reagent pad detects albumin well and globulin poorly, and it reads false positives in alkaline urine above pH 8.0 and in very concentrated samples. That is why a 1+ reading on a strip is not proteinuria. The urine protein-to-creatinine ratio (UPC) is the quantitative test: under 0.2 is non-proteinuric, 0.2 to 0.4 is borderline, and above 0.4 is proteinuric. Because day-to-day variation is real, most clinicians confirm with 2 of 3 samples collected over 2 to 4 weeks before labeling a cat proteinuric. A cat with a UPC of 0.6 and a specific gravity of 1.045 may simply be concentrated; a cat with 0.6 and 1.018 is a different case.
Sediment: 4 buckets, counted per field
Read the sediment at 100x to find what is there, then at 400x to count it. The 4 buckets are cells, casts, crystals, and microorganisms. Cells: more than 5 red cells per high-power field is abnormal, and more than 5 white cells per field suggests inflammation; both need a context, since a free-catch sample from a cat in heat or with cystitis looks the same. Casts: 0 to 2 hyaline casts per low-power field is normal, while granular casts point to tubular injury and broad waxy casts to chronic damage. Crystals: struvite and oxalate are common and only matter alongside pH and stone history. Microorganisms: bacteria, yeast, or an occasional parasite egg, best confirmed by culture.
Three extras worth reading
Glucose appears in urine once blood glucose passes the renal threshold, usually near 250 mg/dL, so glucosuria with a normal blood glucose points to a tubular problem rather than diabetes. Ketones at 1+ or higher in an anorexic cat mean fat is being burned faster than it is cleared. Bilirubin is different from dogs: cats conjugate and excrete it readily, so any bilirubin on the pad usually deserves a look rather than a shrug. Normal water intake is 20 to 45 mL/kg per day, and urine output of 1 to 2 mL/kg per hour is the expected range; a cat producing more than 50 mL/kg per day is polyuric whatever the strip says.
The numbers at a glance
| Item | Reference | Cut point 1 | Cut point 2 | Repeat window |
|---|---|---|---|---|
| Specific gravity | 1.035 to 1.060 | 1.013 to 1.034 poorly concentrated | below 1.008 dilute | every visit, 6 months |
| pH | 6.0 to 6.5 | below 6.0 favors oxalate | above 6.6 favors struvite | fresh sample only, 30 minutes |
| UPC | below 0.2 | 0.2 to 0.4 borderline | above 0.4 proteinuric | 2 of 3 samples in 2 to 4 weeks |
| White cells | below 5 per hpf | 5 to 10 per hpf equivocal | above 10 per hpf inflammatory | culture in 24 to 48 hours |
| Urine output | 1 to 2 mL/kg/hour | above 50 mL/kg/day polyuric | below 1 mL/kg/hour oliguric | log 3 days before visit |
Five things to do with the report
- Ask for specific gravity by refractometer, and write it next to the creatinine value.
- Request UPC whenever the strip shows 1+ protein or higher, and confirm before calling it proteinuria.
- Keep every urinalysis tied to the collection method: cystocentesis, free catch, or manual expression.
- Photograph the sediment report; crystal type and cast type rarely come back identical twice.
- Repeat any abnormal value once in 2 to 4 weeks before changing the cat's routine.
Stop reading reports and call the clinic if the cat strains for more than 10 minutes without producing urine, cries while urinating, has blood in the urine with a blocked posture, or has not urinated in 12 hours. A urethral obstruction in a male cat is fatal within 24 to 48 hours untreated. For how urine findings fit with the rest of the panel, see white cell counts and feline vision, and the breed quiz for breed-linked urinary risk.
Terms mentioned in this article
Frequently asked
Is a urine specific gravity of 1.035 good or bad?
It depends on the bloodwork. At 1.035 or higher the kidney still concentrates well, which is a good sign in a healthy cat and also a sign of dehydration or prerenal azotemia in a sick one. The worrying pairing is azotemia with a specific gravity of 1.020, because that means concentrating ability is being lost.
Does 1+ protein on the strip mean proteinuria?
Not on its own. The reagent pad reads albumin well and globulin poorly, and it turns false positive in urine above pH 8.0 or in very concentrated samples. Confirm with a urine protein-to-creatinine ratio: under 0.2 is normal, 0.2 to 0.4 is borderline, and above 0.4 is proteinuric, ideally on 2 of 3 samples collected over 2 to 4 weeks.
How fast does a urine sample have to be read?
Within 30 minutes for cells, casts, and pH. If the laboratory is off site, refrigerate at 2 to 6 °C for no more than 6 hours and warm the sample back to room temperature before measuring specific gravity with a refractometer. Bacteria multiply and crystals precipitate quickly, so an old sample can invent findings that were never there.