Why Is My Dog Or Cat's Urine Nitrite Positive ?













Ron Hines DVM PhD

To see what normal blood and urine values are, go here

For an explanation of causes of most abnormal blood and urine tests, go here

To see how tests are grouped, go here

Nitrite In Your Pet’s Urine - An Indication Of Urinary Tract Infection

Veterinarians usually screen dog and cat urine sample using a paper strip impregnated at different points with chemicals that change color when particular compounds are present in your pet’s urine.

One of those compounds the test looks for is nitrite. Nitrite is produced by certain bacteria. When the test is done correctly and your pet’s urine contains any nitrite, it is quite likely that it has a bacterial urinary tract infection (UTI) - even when no bacteria are seen.




Urine that sits too long at room temperature can give a false-positive due to bacterial contamination and growth while it sat. All urine samples that are obtained during urination are contaminated with bacteria. Given time at room temperature, they will alter several of the test strip results. Out-of-date test strips or those left with the bottle cap off can give false negative or false positive results.

Just because your pet’s urine tested negative for nitrite does not mean that it does not have a urinary tract infection. Not all bacteria produce nitrite and some infections are too low grade to activate the test strip. If the leukocyte esterase (LE) portion of the strip was positive, if too many white blood cells were seen or if your pet is showing the typical signs of a urinary tract infection, it is a good idea to obtain a new clean sample (by catheter or needle) and culture the urine for bacteria - even if the nitrite portion of the test strip was negative.

Complementary Tests :

Microscopic urine sediment examination, examination of the dipstick for a positive leukocyte esterase reaction, bacterial culture of the pet’s urine