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Nitrites in Urine: What a Positive or Negative Result Means

Nitrites in urine usually point to bacteria in the urinary tract, but the result only makes sense next to leukocyte esterase, white blood cells, bacteria and epithelial cells on the same report. Learn what a positive or negative nitrite means, when it is not a UTI, and what happens next.

Published

October 27, 2026

Read time

10 min read

Medically reviewed by

Rhonda Collins, FNP-C

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Nitrites in urine usually mean bacteria are present in the urinary tract, and with urinary symptoms a positive nitrite strongly suggests a urinary tract infection (UTI). Nitrite forms when bacteria convert nitrate, a chemical normally present in urine, into nitrite, so it is not normally found in urine ^[1][2][3]. A positive result is a fairly reliable sign of bacteria. A negative result does not rule out an infection ^[1][3].

The nitrite line also does not stand alone. It is read next to leukocyte esterase, the microscopic white blood cell count, bacteria and epithelial cells on the same urinalysis, and next to whether you have symptoms ^[1][4]. When bacteria are in the urine without symptoms, guidelines advise against treating them in most people, with pregnancy and certain urologic procedures as the main exceptions ^[5][6]. A urine culture confirms which bacteria are growing ^[7].

What the urine nitrite test detects

The nitrite test is a pad on a urine dipstick, read as positive or negative as part of a routine urinalysis ^[1][4]. It does not detect bacteria directly. It detects nitrite, which many bacteria produce from urinary nitrate ^[1][3].

Many gram-negative bacteria and some gram-positive bacteria can make this conversion ^[3]. A positive dipstick nitrite indicates these organisms are present in significant numbers, more than 10,000 per mL ^[3]. On a Mito report this result appears as urine nitrite.

Two features of how nitrite forms explain most confusing results:

• It takes time. Bacteria need about four hours in the bladder to produce nitrites ^[4]. Urine that has not sat in the bladder long enough can read negative even when bacteria are present ^[4].
• Not every bacterium makes it. Some bacteria, such as Enterococcus, do not produce nitrite ^[4].

What a positive nitrite result means

A positive nitrite in someone with urinary symptoms strongly suggests a UTI ^[4]. Nitrite is more specific for a UTI than leukocyte esterase ^[4]. In a summary of studies, mostly of adult women seen in emergency departments, a positive nitrite had a positive likelihood ratio of 13 for a UTI, the highest of any single urinalysis finding ^[4]. An earlier review reported a nitrite specificity of 92 to 100% against culture-confirmed UTI ^[3].

Common UTI symptoms include pain or burning when urinating, a strong need to urinate often, cloudy or strong-smelling urine, and pressure or cramping in the lower abdomen ^[8].

A positive nitrite is still a screening result. A meta-analysis of dipstick studies concluded that positive dipstick results need to be confirmed, and that the dipstick alone is doubtful for ruling an infection in ^[9]. The usual confirmation is a urine culture, which grows bacteria from the sample and identifies them, usually within 24 to 48 hours ^[7].

Reading nitrite with the rest of the urinalysis

A urinalysis has several lines that relate to infection. Each answers a different question, and together they tell you more than nitrite alone.

Some combinations you may see:

• Positive nitrite, positive leukocyte esterase, white cells present, with symptoms. This is the classic UTI pattern ^[4]. A culture identifies the bacteria ^[1][7].
• Positive nitrite, many squamous epithelial cells. The sample may be contaminated with bacteria from the skin ^[4]. A repeat clean-catch sample helps. Even with contamination, white cells or blood in the urine still suggest a UTI ^[4].
• Positive nitrite, no leukocyte esterase, no white cells, no symptoms. This can be bacteria in the urine without infection (see below), contamination or a false positive ^[3][4][6].
• Negative nitrite, negative leukocyte esterase. When both are negative, a UTI is much less likely. In the review above, this combination had a negative likelihood ratio of 0.2 ^[4]. The meta-analysis found that both tests being negative was useful to exclude infection in most groups ^[9].

Negative nitrite with leukocytes in urine

A negative nitrite with positive leukocyte esterase can still be a UTI. Nitrite is specific but not very sensitive, so a negative result does not rule out infection ^[3]. The earlier review reported nitrite sensitivity of only 19 to 48% for culture-confirmed UTI ^[3]. Three reasons explain most of the misses:

• Bacteria that do not make nitrite. Enterococcus is one example ^[4].
• Short time in the bladder. Bacteria need about four hours in the bladder to make nitrite, so frequent urination often gives a false negative ^[4].
• Dilute urine or interference. High urine specific gravity and vitamin C can cause a false-negative nitrite ^[3][4]. In a study of culture-confirmed Enterobacterales infections that tested nitrite negative, the authors named dilute urine and vitamin C among the likely causes, and concluded that a standard urine culture is needed to rule out a UTI ^[10].

Leukocytes without nitrites can also have a cause other than a bladder infection. Leukocyte esterase is present with inflammation and infection more generally, including sexually transmitted infections ^[4]. White cells in the urine can come from kidney stones ^[4]. Other causes of white cells with a negative culture include urethritis, viral infections, bladder tumors, exercise and glomerulonephritis ^[3]. Contamination of the sample can also turn the leukocyte esterase pad positive ^[3][4].

So with leukocytes but no nitrites, symptoms matter most. With urinary symptoms, a urine culture is the next step ^[4]. Without symptoms, a repeat clean-catch sample is a reasonable way to check whether the finding persists.

Nitrites in urine but no UTI

Bacteria in the urine do not always mean an infection. Asymptomatic bacteriuria means bacteria are growing in the urine but there are no urinary symptoms ^[6]. The Infectious Diseases Society of America (IDSA) defines it in a voided sample as 100,000 or more colony-forming units per mL on culture, whether or not white cells are also present ^[5].

It is a common finding in many groups, including healthy women ^[5]. A positive nitrite, which reflects bacteria, can therefore appear in someone with no infection to treat.

The 2019 IDSA guideline recommends against screening for or treating asymptomatic bacteriuria in ^[5]:

• healthy premenopausal, nonpregnant women and healthy postmenopausal women;
• people with diabetes;
• older adults living in the community who are functionally impaired, and older adults in long-term care.

The guideline recommends screening and treatment in two main situations: pregnancy, and before endoscopic urologic procedures that injure the lining of the urinary tract ^[5]. MedlinePlus lists a few other situations, such as a recent kidney transplant ^[6]. The reason for restraint is that treating bacteria that cause no harm adds to unnecessary antibiotic use, which promotes antibiotic resistance ^[5], and can make later infections harder to treat ^[6].

Bacteria in the urine is not the only explanation for a positive nitrite without symptoms. The pad can also turn positive from a contaminated sample, a dipstick exposed to air, or phenazopyridine ^[3][4]. Strips left exposed to air give false positives often: after one week of exposure, about one third of strips read positive, and after two weeks about three quarters ^[3].

Whether a positive nitrite without symptoms needs follow-up depends on your situation, which is a question for your doctor. Pregnancy and a planned urologic procedure are the clearest reasons to follow it up even without symptoms ^[5][6].

Nitrites in urine during pregnancy

Pregnancy is the main exception to leaving symptom-free bacteria alone. The IDSA guideline strongly recommends screening for and treating asymptomatic bacteriuria in pregnant women ^[5]. To diagnose it, a urine sample is sent for culture ^[6].

In a meta-analysis of dipstick accuracy, the nitrite test was highly accurate in studies of pregnant women ^[9]. It is still a screen, and the culture is what confirms bacteriuria and guides any treatment ^[6][7]. A positive nitrite in pregnancy should go to your prenatal clinician, who decides on culture and treatment. Pregnant people with a UTI and a fever, or who feel ill, may need hospital care ^[8].

False positives and false negatives

Dipstick results can be wrong in both directions ^[3][4]:

Handling matters too. Delays of more than two hours between collection and examination often make urinalysis results unreliable, so urine that cannot be examined promptly should be refrigerated ^[3].

What happens next after a nitrite result

1. Match the result to your symptoms. A positive nitrite with urinary symptoms points to a UTI ^[4]. Without symptoms, bacteria may be present without infection ^[5][6].
2. Read the other infection lines. Look at leukocyte esterase, the microscopic white cell count, bacteria and squamous epithelial cells, as in the table above ^[4].
3. Repeat a clean sample when the result is unclear. For UTI testing, a midstream clean-catch sample is the standard ^[4]. If many squamous cells suggest contamination, a repeat clean-catch sample gives a more reliable reading ^[4].
4. Get a urine culture when an infection is suspected. A culture is recommended when UTI symptoms are present ^[4]. It identifies the bacteria and helps decide which treatment, if any, is needed ^[1][7]. Results take 24 to 48 hours ^[7].

The Urinalysis, Routine Test includes the nitrite and leukocyte esterase dipstick pads and a microscopic exam for white cells, bacteria and epithelial cells, so one sample covers every line in the table above. When the culture step is likely to be needed, the Urinalysis, Complete Test with Reflex to Urine Culture runs a urine culture automatically if the urinalysis shows signs of a possible infection.

For other findings on the same report, see what blood in urine test results mean, what foamy urine can mean, what mucus in urine means, bilirubin in urine and urobilinogen in urine.

When to get prompt care

Contact your doctor if you have symptoms of a UTI ^[8]. Contact them right away if you have signs that an infection may have reached the kidneys ^[8]:

• back or side pain;
• fever or chills;
• vomiting.

Also get in touch if UTI symptoms come back shortly after treatment ^[8]. In older people, confusion or other mental changes can be the only sign of a UTI ^[8]. If you are pregnant, contact your prenatal clinician about any positive nitrite or urinary symptoms, and seek care promptly for fever or feeling ill ^[5][8].

References

1. MedlinePlus. Nitrites in urine. National Library of Medicine. Last updated November 5, 2024.
2. MedlinePlus. Urinalysis. National Library of Medicine. Reviewed January 1, 2025.
3. Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. Am Fam Physician. 2005;71(6):1153-1162.
4. Hitzeman N, Greer D, Carpio E. Office-based urinalysis: a comprehensive review. Am Fam Physician. 2022;106(1):27-35B.
5. Nicolle LE, Gupta K, Bradley SF, et al. Clinical practice guideline for the management of asymptomatic bacteriuria: 2019 update by the Infectious Diseases Society of America. Clin Infect Dis. 2019;68(10):e83-e110. PMID: 30895288
6. MedlinePlus. Asymptomatic bacteriuria. National Library of Medicine. Reviewed July 23, 2024.
7. MedlinePlus. Urine culture. National Library of Medicine. Reviewed October 9, 2024.
8. MedlinePlus. Urinary tract infection: adults. National Library of Medicine. Reviewed July 23, 2024.
9. Devillé WL, Yzermans JC, van Duijn NP, et al. The urine dipstick test useful to rule out infections. A meta-analysis of the accuracy. BMC Urol. 2004;4:4. PMID: 15175113
10. Lopes Araújo-Filho CE, Santos Galvão V, Fernandes do Espírito Santo R, et al. Nitrite-negative results in urinary tract infection by Enterobacterales: does the nitrite dipstick test have low sensitivity? J Med Microbiol. 2023;72(2). PMID: 36762527

Frequently asked questions

What causes positive nitrites in urine?

Nitrites form when bacteria in the urine convert nitrate, a chemical normally found in urine, into nitrite. Many of the bacteria that cause urinary tract infections can do this, so a positive nitrite usually means bacteria are present in significant numbers. A positive result can also come from a contaminated sample, a test strip that was left exposed to air, or the medicine phenazopyridine. A urine culture confirms whether bacteria are really growing and which ones.

Can you have nitrites in urine but no UTI?

Yes. Some people have bacteria in their urine without any urinary symptoms, which is called asymptomatic bacteriuria. It is a common finding, including in healthy women. The Infectious Diseases Society of America advises against screening for or treating it in most people, with pregnancy and certain urologic procedures as the main exceptions. A positive nitrite can also come from a contaminated sample or a strip exposed to air.

What kills nitrites in urine?

Nitrite is not a germ. It is a chemical that bacteria make in the bladder, so it disappears from urine when the bacteria making it are gone. A later negative nitrite is not proof that an infection has cleared, though: frequent urination, dilute urine, vitamin C and bacteria that do not make nitrite can all give a negative result while bacteria are still present. When it matters, a urine culture after treatment is the test that checks whether the bacteria are gone.

What does leukocytes but no nitrites in urine mean?

Leukocyte esterase is a sign of white blood cells. With a negative nitrite it can still be a urinary tract infection, because some bacteria, such as Enterococcus, do not make nitrite and because nitrite needs about four hours in the bladder to form. It can also come from a contaminated sample, a sexually transmitted infection, kidney stones or other inflammation. Symptoms, the microscopic white cell count and a urine culture decide which.

Are nitrites in urine during pregnancy serious?

Nitrites in pregnancy should always be followed up with your prenatal clinician, even without symptoms. Pregnancy is one of the few situations where guidelines recommend screening for and treating bacteria in the urine when there are no symptoms, because the risks of an untreated infection are higher. A urine culture confirms the result before any decision about treatment.