Cat urinalysis — step-by-step interpretation for owners

Cat urinalysis — step-by-step interpretation for owners

Wondering what a full interpretation looks like? See a sample report →

The Three Layers of a Cat Urinalysis

A urinalysis is not one test but three examinations stacked on top of each other, and reading the report well means knowing which layer each line belongs to. The first layer is physical: the colour and clarity of the urine and, most importantly, how concentrated it is. The second is chemical, the familiar dipstick that flags protein, glucose, ketones, blood, bilirubin and pH. The third is the sediment – what is actually floating in the urine once it is spun down and placed under a microscope, from red and white cells to crystals, casts and bacteria. A finding only earns its meaning when it is set against the other two layers, which is why a result that looks alarming in isolation can be reassuring in context, and why a quiet-looking strip can still hide a problem the microscope reveals.

Why Urine Concentration Outranks Almost Everything Else

If there is a single number a veterinarian reaches for first in a cat, it is the specific gravity – the measure of how concentrated the urine is. Healthy feline kidneys are remarkably good at conserving water, so a cat that is even mildly short of fluid should be producing strongly concentrated urine. When the urine stays dilute in a cat that ought to be conserving water, that mismatch is one of the earliest and most easily overlooked signals that the kidneys are losing their concentrating ability. This is exactly why urine and blood are read as a pair: a rise in the kidney markers means something quite different depending on whether the urine is concentrated or dilute. The detail is woven through the way veterinarians interpret kidney markers such as creatinine, BUN and SDMA, and it sits at the heart of how creatinine is staged in feline chronic kidney disease. A urine concentration that fails to rise alongside a climbing SDMA is far more telling than either result on its own.

Where the Normal Lines Sit

Reference intervals shift between laboratories because they depend on the analyser and method used, so the range printed on your own cat’s report is always the final word. As an evidence-based guide, the verified feline values for the quantitative parts of a urinalysis and its closely linked blood markers are set out below. Specific gravity is reported by the lab’s refractometer scale; the urine protein-to-creatinine ratio is the standard way protein loss is quantified once the sediment is quiet.

See the full reference intervals for the cat — every value cited to the laboratory document or paper it came from.

Note that urine dipstick pads for protein, glucose, blood and pH are reported as semi-quantitative grades, not fixed numbers; those grades are assay-specific, and the lab’s own scale governs how each is read.

Reading the Dipstick – and Where It Misleads

The chemistry strip is fast and useful, but each pad answers a narrow question and several are easy to over-read in a cat. A positive protein pad is meaningless until it is weighed against the urine concentration and the sediment, because concentrated urine and an active sediment can both light up the protein pad without any true kidney leak. Glucose on the strip points toward checking blood sugar but is never a diagnosis on its own. And the blood pad is famously unspecific: it reacts to intact red cells, to free hemoglobin and to muscle pigment alike, so the microscope is what tells them apart. The table below pairs each common dipstick line with the question it really answers.

What the Sediment Adds Under the Microscope

The sediment is where a urinalysis turns from a list of grades into an actual picture. Spinning the urine down concentrates the cells, crystals and casts that the dipstick can only hint at, and it is here that ambiguous strip results are resolved. White cells together with bacteria point toward an infection or inflammation of the lower urinary tract; red cells confirm that a positive blood pad really means bleeding rather than pigment; casts, which are moulds of the kidney tubules, suggest the trouble reaches up into the kidney itself rather than just the bladder. Crystals are the most over-interpreted finding of all – many form simply because the sample sat before it was examined, so a few crystals in a comfortable cat with no signs are often left alone, while the same crystals in a straining cat passing blood become part of a stone work-up. Whether bacteria seen on the slide truly represent infection also depends heavily on how the sample was collected, which is taken further in the dedicated guide to working up bacteriuria in cats.

How the Urinalysis Talks to the Blood Panel

A urinalysis is at its most powerful when it is read beside a blood panel, because the two together let a veterinarian separate look-alike problems. Dilute urine alongside rising kidney markers points toward genuine kidney disease and shapes how chronic kidney disease is monitored over time; the same blood markers with appropriately concentrated urine lean instead toward dehydration. Glucose in the urine sends the question back to the blood, where a raised reading might reflect true diabetes or merely a stress spike, and a fructosamine helps settle which. Protein loss in the urine takes on a different weight depending on the blood albumin and globulin picture. And in an older cat, a urinalysis that does not quite fit the blood findings can be the nudge to check whether hyperthyroidism is masking the true state of the kidneys. For a fuller map of how these threads connect, the complete cat blood panel reading guide is the natural companion to this page.

Why Sample Collection Quietly Shapes Every Result

How the urine was obtained changes how confidently each finding can be read, and it is the part of a urinalysis owners hear least about. A sample drawn straight from the bladder with a fine needle is the cleanest for judging infection, because it bypasses everything the urine would otherwise pick up on its way out. A free-catch sample is more convenient but can gather contaminants and a few cells from the lower tract, while urine scooped from a litter tray is the least reliable of all. Time matters just as much as method: urine that has sat for hours can grow bacteria and throw down crystals that were never there in the living cat, so a sample examined while fresh avoids a whole category of false alarms. None of this changes the underlying biology, but it changes the confidence with which a veterinarian reads the protein, the sediment and the bacterial findings – which is why the collection note on the report is part of the interpretation, not a footnote.

Putting the Layers Back Together

Reading a cat’s urinalysis well is less about any one value than about how the three layers agree or disagree. Concentrated urine with a clean strip and a quiet sediment is the picture of a kidney doing its job. Dilute urine with rising blood markers tells a kidney story that the protein and sediment then help to stage. A lit-up blood pad means one thing with red cells under the microscope and quite another without them. Because no single line settles a question, the natural next step after an abnormal result is rarely treatment aimed at the urinalysis itself – it is confirming the pattern, often by repeating the test on a fresh, well-collected sample, adding a UPC, or pairing it with a full blood-test interpretation and, where appropriate, imaging. Tracked over time, a urinalysis becomes one of the most informative low-cost windows onto a cat’s kidneys, bladder and metabolism – provided each layer is read for what it can, and cannot, say.

How a Urinalysis Is Read Beside the Blood Panel

Urine and blood answer different halves of the same question, and neither is complete alone. The clearest example is the kidney: a rise in the blood markers means littl