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Blood Test Tracker

Urine Nitrite (Dipstick)

Checks for nitrite, a chemical some urinary bacteria make. A positive result can be an early clue to a urinary tract infection.

AI-verified against cited sources. Awaiting expert reviewAlso called NIT, UA NitriteLOINC 5802-4

What it is

Urine normally has no nitrite. Some bacteria that infect the bladder change nitrate, a chemical that comes from food and your body, into nitrite. A test strip dipped in your urine changes color when nitrite is there. The result is printed as negative or positive. It is one line of a urinalysis and is read together with the white blood cell (leukocyte esterase) result and your symptoms.

Why it matters

A positive result can be an early clue that bacteria are growing in the urinary tract. It helps your clinician decide whether to look further, for example with a urine culture. A negative result tells you less. Many bacteria do not make nitrite, and the test can miss an infection if the urine has not been in the bladder long enough. Your symptoms and the rest of the urinalysis matter as much as this one line.

If it’s high

A positive result means the strip found nitrite in your sample. This often happens when bacteria that can cause a urinary tract infection (UTI) are present. It can also come from a sample that picked up germs from the skin or sat too long, or from a strip that was exposed to air. Your clinician will read it along with your symptoms and the other urinalysis results.

Common causes

  • A urinary tract infection (UTI) caused by bacteria that turn nitrate into nitrite, such as E. coli
  • Bacteria in the urine that are not causing symptoms (asymptomatic bacteriuria)
  • Germs from the skin or genital area getting into the sample
  • A sample that sat for hours before it was tested
  • A test strip that was left open to the air
  • Phenazopyridine, a urinary pain-relief medicine that colors the urine

What can help

  • Talk with your clinician soon, especially if you have symptoms such as burning when you urinate or needing to go often
  • Ask whether a urine culture would help confirm the result
  • If you need to give another sample, ask how to collect a clean-catch midstream sample

What can affect your result

  • Time in the bladder: bacteria need about 4 hours to make nitrite, so frequent urination can cause a false-negative result
  • Diet: the test needs nitrate from food, so a low-nitrate diet can cause a false-negative result
  • Type of bacteria: Enterococcus, other streptococci and Candida do not make nitrite
  • Vitamin C (ascorbic acid) can cause a false-negative result
  • Very concentrated urine can cause a false-negative result
  • Sample collection and storage: contamination or delay can cause a false-positive result
  • Strip handling: exposure to air can make a strip turn positive on its own
  • High vitamin C (ascorbic acid) intake can make the result falsely negative.
  • Phenazopyridine, a urinary pain-relief medicine, colors the urine and can make the result falsely positive.
  • A test strip left open to the air can turn positive on its own.
  • Germs from the skin or genital area getting into the sample can make the result falsely positive. A clean-catch midstream sample helps.
  • Urine that sits for hours before testing can give unreliable results. Samples should be tested promptly or refrigerated.
  • Very concentrated urine, a low-nitrate diet, or very frequent urination (less than about 4 hours in the bladder) can make the result falsely negative.
  • Some bacteria, such as Enterococcus, do not make nitrite, so an infection with them can give a negative result.

A first-morning sample is often used, because bacteria need about 4 hours in the bladder to make nitrite. A clean-catch midstream sample lowers the chance of contamination. The result reflects only the sample you gave. It can change from one sample to the next.

When to talk to a clinician

Contact a clinician soon if you have signs of a urinary tract infection. These include burning when you urinate, needing to go often, cloudy or bad-smelling urine, and pain low in your belly. A fever can mean the infection has reached the kidneys, so call promptly if you have a fever. Confusion or unusual weakness also needs prompt attention, especially in older adults. If you are pregnant, tell your clinician about any positive nitrite result, even if you feel fine. For babies and young children, a positive result from a collection bag is usually checked again with a cleaner sample.

Questions you could ask

  • Could any of my supplements, such as vitamin C, change this test?
  • If my symptoms continue even though nitrite is negative, what should we check next?
  • Should we send a urine culture to confirm this result?
  • Could my sample have picked up germs from the skin, and should I give another clean-catch sample?
  • Which symptoms should make me contact you sooner?

Questions people ask

My nitrite is negative but I have UTI symptoms. Could I still have an infection?

Yes. Many bacteria do not make nitrite, and the strip can miss an infection if your urine was not in your bladder for about 4 hours or if you eat little nitrate. A negative result does not rule out a UTI, so tell your clinician about your symptoms.

My nitrite is positive but I feel fine. What could that mean?

Sometimes bacteria are present in the urine without causing symptoms. A sample that picked up skin germs or sat too long can also test positive. Your clinician may ask for a clean-catch sample or a urine culture, and will look at the whole urinalysis rather than one line.

Does vitamin C change this test?

Yes. High vitamin C intake can make a nitrite test read falsely negative. Tell your clinician or the lab about any vitamin C you take.

Are at-home UTI strips reliable?

They check for nitrites and white blood cells, but they do not always give accurate results and can say you do not have a UTI when you do. If you have symptoms, ask your clinician which test is right for you.

Show the science and sources

For clinicians and researchers

Strips use a Griess-type color reaction: nitrite in the urine turns the pad pink. Nitrite appears only when bacterial nitrate reductase converts urinary nitrate, which needs enough dietary nitrate and roughly 4 hours of bladder dwell time. Enterobacteriaceae and most non-fermenters reduce nitrate. Enterococcus, other streptococci and Candida do not (Mambatta 2015). One report puts the Griess test's detection limit at about 0.1 ug/mL. Against culture, specificity is high and sensitivity is low and varies by setting. A meta-analysis of 70 publications found sensitivity of 45-60% in most situations and specificity of 85-98% (Deville 2004). AFP 2005 gives sensitivity of 19-48% and specificity of 92-100%. AFP 2022 gives a positive likelihood ratio of 13 for UTI, and 0.2 when leukocyte esterase and nitrite are both negative. A positive result is therefore useful and a negative result does not rule out UTI. False negatives come from high specific gravity, short bladder incubation, vitamin C, a low-nitrate diet and non-nitrate-reducing organisms; AFP 2005 also lists urine pH below 6.0 and elevated urobilinogen. False positives come from contamination, phenazopyridine and strips exposed to air (about one third of strips after one week, per AFP 2005). Strips are read visually or by a reflectance meter and give a presence call only. They do not identify the organism or its antibiotic susceptibility, which need culture. In infants, a positive nitrite or leukocyte esterase on a bag specimen should be followed by catheter or suprapubic collection (AFP 2022).

LOINC 5802-4 (primary), 50558-6, 32710-6. Specimen: urine.

Sources

  1. Nitrites in Urine, MedlinePlus (U.S. National Library of Medicine)
  2. Office-Based Urinalysis: A Comprehensive Review, American Family Physician 2022;106(1):27-35B (2022)
  3. Urinalysis: A Comprehensive Review, American Family Physician 2005;71(6):1153-1162 (2005)
  4. The urine dipstick test useful to rule out infections. A meta-analysis of the accuracy, BMC Urology 2004;4:4 (2004)
  5. Reliability of dipstick assay in predicting urinary tract infection, Journal of Family Medicine and Primary Care 2015;4(2):265-268 (2015)
  6. Urinalysis, Complete With Microscopic Examination (test 003772), Labcorp
  7. Urinalysis, Complete (test 003772) sample patient report with reference intervals, Labcorp (2026)
  8. LOINC codes verified with the NLM Clinical Tables LOINC search (e.g. 5802-4), U.S. National Library of Medicine

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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