Nitrites in urine (dipstick) in cats and dogs
Many urine dipsticks have a nitrite pad, so this line can appear on a pet’s urinalysis. In people it is a quick hint of a bladder infection, but in cats and dogs it is not considered valid, and vets do not use it to decide whether bacteria are present. Bacteria are looked for under the microscope and confirmed by urine culture.
What it shows
Many urine dipsticks carry a nitrite pad. Dipsticks were designed mainly for human medicine, and there the nitrite pad serves as an indirect sign of bacteria in urine. So the line can appear on a pet’s urinalysis simply because it is printed on the strip.
In cats and dogs this pad is regarded as not valid, together with the white blood cell (leukocyte) and specific gravity pads of the same strip, and veterinary guides advise not to use it. These pads are not used for veterinary patients. A nitrite result on the form is therefore not read as proof of an infection, nor as proof that there is none.
Higher than reference — what it may be a sign of
A positive nitrite pad in a cat or dog is not a diagnosis of a urinary tract infection. At most it is a reason to look carefully at the rest of the urinalysis. What really points to bacteria:
- Bacteria in the sediment — seen under the microscope; rods are easier to recognise than small round cocci, which can be confused with tiny crystals, cell debris and fat droplets.
- White blood cells in the sediment — a sign of inflammation in the urinary tract.
- Bacteria grown on urine culture — the test that confirms that bacteria are alive and shows which ones they are.
Lower than reference
A negative nitrite pad does not exclude a urinary tract infection in a cat or dog. In one study of dog and cat urine samples, positive nitrite results were so few that agreement between readers could not even be assessed. More broadly, a urinalysis on its own is not reliable for excluding an infection; if the vet suspects one, the answer comes from culture.
Look at together with
- Bacteria in urine (sediment and culture) — the main way to find and confirm bacteria.
- Cells in the urine sediment — white and red blood cells; the strip’s leukocyte pad is not reliable in animals either.
- Urine specific gravity — measured with a refractometer, because the strip’s specific gravity pad is not valid in animals.
- Urine pH, protein and blood — pads of the same strip that vets do use.
Units and conversion
The nitrite pad has no unit and no grades: the result is printed as “negative” or “positive” (sometimes shortened to “neg” and “pos”). There is nothing to convert. In the app the result is kept exactly as written on the form, and it is not placed on a chart.
Reference range
The reference range is on your lab’s form; it is usually “negative”. In cats and dogs this expected value does not carry the meaning it has in people: a negative result does not show that urine is free of bacteria, and a positive result does not prove an infection. Whether bacteria are present is decided by the sediment and, above all, by urine culture — best from urine collected with a needle straight from the bladder (cystocentesis). Bacteria seen under the microscope in such a sample matter regardless of their number, because urine in the bladder is normally sterile.
Cats and dogs
In cats the nitrite field of the dipstick is described as unreliable, and the leukocyte field is often falsely positive. A reliable diagnosis of a urinary tract infection in a cat needs a positive urine culture. The other pads of the strip and the sediment are read as usual.
The same applies to dogs: the nitrite pad is not valid and is not used for decisions. Positive nitrite results are rare in canine samples, which makes the pad even harder to judge. Bacteria in a dog’s urine are looked for in the sediment and confirmed by culture.
Add a lab form — Pet Tracker Space recognises the lines, keeps the form’s units and draws each indicator over time with your lab’s reference band.
Sources
- Whitbread TJ. Urinalysis. Merck Veterinary Manual
- Rizzi TE. Urinalysis in companion animals, part 2: evaluation of urine chemistry & sediment. Today’s Veterinary Practice, 2014
- Cervone M et al. Inter-observer agreement among experienced and inexperienced observers and an automated device for dipstick urinalysis in dogs and cats. J Vet Diagn Invest, 2023 (PMC)
- Dorsch R, Teichmann-Knorrn S, Sjetne Lund H. Urinary tract infection and subclinical bacteriuria in cats: a clinical update. J Feline Med Surg, 2019
- eClinPath (Cornell University) — Urinalysis: infectious agents
- Merck Veterinary Manual — The urinary system in animals
This page explains what a lab value means. It is not a diagnosis and not a substitute for your veterinarian — only they can interpret results for your pet.