Nitrite in urine: what a positive nitrite means, and nitrite negative but leukocytes positive
Nitrite in urine · Urinalysis (dipstick) · reported in Reported as negative or positive (qualitative); some analyzers add trace
Nitrite in urine is a chemical made by certain bacteria, and a urine dipstick tests for it as a quick sign of a bacterial urinary tract infection. The normal result is negative: healthy urine contains nitrate from the diet but no nitrite. The most common reason the pad turns pink is an infection with E. coli or a related bacterium that converts nitrate to nitrite while the urine sits in the bladder. A positive nitrite is one of the most specific findings on a urinalysis, correct about 95 percent of the time.
The catch is sensitivity. The test picks up only around half of true infections, because the bacteria need about four hours in the bladder to make enough nitrite, because some common organisms (enterococci, staphylococci, pseudomonas, group B strep) do not make it at all, and because dilute urine, frequent urination and vitamin C all mask it. So a negative nitrite does not rule out a UTI. This is why the result is read together with the leukocyte esterase pad and the white-cell count: nitrite negative but leukocytes positive is still very often an infection.
A positive nitrite in someone with burning, urgency and frequency is usually enough to start treatment while a culture confirms the organism. A positive nitrite with no symptoms is more complicated: it may be asymptomatic bacteriuria, which is common in older adults and people with catheters and is deliberately not treated outside pregnancy, or it may be an old sample in which bacteria multiplied in the cup.
Nitrite in urine at a glance
- What it is: a dipstick test for nitrite, produced when nitrate-reducing bacteria (E. coli, Klebsiella, Proteus and relatives) grow in urine; a marker of bacterial UTI.
- Normal: negative. There is no numeric range; the pad is either negative or positive (a few analyzers report trace).
- Positive nitrite is about 95 percent specific for a bacterial UTI, and with symptoms and a positive leukocyte esterase the probability is above 90 percent.
- Negative nitrite misses about half of infections: urine held less than 4 hours, organisms that do not make nitrite, dilute urine and vitamin C all cause false negatives.
- Nitrite negative but leukocytes positive: still commonly a UTI (especially enterococcus or staphylococcus), or an STI, a stone or contamination; the culture decides.
- Next step: a urine culture if you have symptoms; a first-morning clean-catch repeat if the result is unexpected or you have no symptoms.
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What Nitrite in urine measures
Nitrate from vegetables and processed meats passes through the kidneys into urine. Many gram-negative bacteria, particularly the Enterobacteriaceae family (E. coli, which causes 75 to 90 percent of uncomplicated UTIs, plus Klebsiella, Proteus, Enterobacter and Citrobacter), carry an enzyme called nitrate reductase that converts nitrate to nitrite. The dipstick pad uses the Griess reaction: nitrite reacts with an aromatic amine to form a diazonium compound, which couples with a second reagent to make a pink dye within 60 seconds. The pad detects about 0.05 to 0.1 mg/dL of nitrite, roughly the amount produced by 100,000 bacteria per millilitre after a few hours.
Three things are needed for a positive result: a nitrate-reducing organism, nitrate in the urine, and time. Bacteria in urine that has been in the bladder for under four hours have not made enough nitrite, so the first urine of the morning is the best sample and a sample passed an hour after the previous one is the worst. People eating little nitrate (some restrictive diets, tube feeding) or on long courses of antibiotics may also test negative despite infection. Across studies the sensitivity is about 45 to 60 percent and the specificity 85 to 98 percent.
False positives are less common but real. A sample left at room temperature for hours lets contaminating bacteria grow and make nitrite in the cup. Phenazopyridine (the orange urinary painkiller), beetroot and other pigments can discolour the pad. Dipsticks exposed to air or stored past their date can turn pink on their own. Vitamin C in the urine, by contrast, blocks the reaction and gives a false negative, which matters for people taking large supplements.
Normal range for Nitrite in urine
Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.
| Group | Typical range (Reported as negative or positive (qualitative); some analyzers add trace) | Notes |
|---|---|---|
| Negative | Normal | No detectable nitrite. Does not exclude infection: about half of culture-proven UTIs test nitrite negative. |
| Trace (some analyzers) | Borderline | A faint reaction; often early infection, a short bladder dwell time or dilute urine. Repeat on a first-morning sample and read with leukocyte esterase. |
| Positive | Abnormal | Nitrate-reducing bacteria are present at roughly 100,000 per mL or more. With symptoms, a UTI is very likely; a culture identifies the organism. |
| Nitrite positive and leukocyte esterase positive | Strongly suggests bacterial UTI | In a woman with typical symptoms the positive predictive value is above 90 percent; treatment is usually started while the culture is pending. |
| Nitrite positive, leukocyte esterase negative | Possible UTI or an old sample | White cells may have broken down in old or dilute urine, or bacteria grew in the cup. Check symptoms, collection time and repeat if unsure. |
| Nitrite negative, leukocyte esterase positive | Possible UTI or other inflammation | Common with enterococcus, staphylococcus, pseudomonas and group B strep, with short dwell time, or with STI, stone, interstitial cystitis and contamination. Culture decides. |
| Both negative | UTI unlikely in low-risk adults | Both negative lowers the probability of infection to roughly 5 to 10 percent in a symptomatic woman; a culture is still sent if symptoms are strong, or in pregnancy, men and children. |
Positive nitrite in urine
A positive nitrite means bacteria capable of reducing nitrate were growing in your urine, almost always at the concentration of a true infection. In a woman with burning, urgency and frequency and no fever, a positive nitrite points to uncomplicated cystitis, most often E. coli, and most clinicians treat on that basis, sending a culture to confirm the organism and its sensitivities. In men, children, pregnant women, people with diabetes or a catheter and anyone with fever or flank pain, the culture matters more because the infection is more likely to be complicated or to involve the kidney.
A positive nitrite without symptoms needs context. Bacteria living in the bladder without causing illness (asymptomatic bacteriuria) affect 1 to 5 percent of young women, up to 20 percent of women over 80, a quarter to half of residents of care homes and essentially everyone with a long-term catheter. These people often test nitrite positive, and the Infectious Diseases Society of America recommends not treating them except in pregnancy and before urologic procedures, because antibiotics do not reduce symptoms, kidney infections or deaths and do increase resistance. The other explanation for an unexpected positive is a sample that sat out for hours or a contaminated collection.
What a positive nitrite does not tell you is which organism or how far the infection has spread. Enterococci and staphylococci never trigger it, so a negative result with white cells can still be a bacterial UTI, and a positive result with fever, back pain or vomiting means the kidney is probably involved regardless of how pink the pad is.
Common causes
Bladder infection with E. coli
E. coli causes most UTIs and reliably reduces nitrate, so it is the usual reason for a positive pad. Leukocyte esterase, white cells and bacteria on microscopy are typically present with it.
Infection with Klebsiella, Proteus, Enterobacter or Citrobacter
These related gram-negative bacteria also make nitrite. Proteus additionally makes urine alkaline (pH above 8) and is associated with struvite stones.
Kidney infection (pyelonephritis)
The same organisms that cause cystitis climb to the kidney; nitrite is positive with heavy pyuria, white-cell casts, fever and flank pain.
Asymptomatic bacteriuria
Bacteria colonising the bladder without illness, common in older women, people with diabetes and care-home residents. Nitrite positive but no symptoms; not treated outside pregnancy and urologic surgery.
Urinary catheter
Long-term catheters are always colonised, usually by nitrate-reducing organisms. A positive nitrite from a catheter sample does not mean infection unless there is fever, pain or other systemic signs.
Old or improperly stored sample
Urine left at room temperature for more than two to four hours lets skin or genital bacteria multiply and produce nitrite in the cup, a false positive that disappears on a fresh, refrigerated sample.
Phenazopyridine and urine pigments
The orange-red color of phenazopyridine, and occasionally beetroot or other dyes, can discolour the nitrite pad so it reads positive. Tell the lab if you are taking it.
Contaminated collection
Bacteria from the vagina, foreskin or skin can enter a poorly collected sample; with many squamous epithelial cells and no white cells, a clean-catch repeat is more useful than antibiotics.
Expired or air-exposed dipsticks
Strips exposed to air or humidity, or past their expiry date, can turn pink spontaneously, which matters for home-testing kits stored in a bathroom.
Symptoms that can go with it
- Burning or stinging when passing urine
- Urgency, frequency and passing small amounts
- Pressure or ache low in the belly
- Cloudy, foul-smelling or blood-tinged urine
- Fever, chills, nausea, vomiting or flank pain (suggests kidney infection)
- In older adults: new confusion, drowsiness or falls, sometimes with no urinary symptoms
- No symptoms at all (asymptomatic bacteriuria, catheter colonisation or an old sample)
Read it alongside
- Leukocyte esterase — the dipstick test for white cells; both positive makes a bacterial UTI very likely, and leukocyte esterase positive with nitrite negative is the most common pattern in true infections the nitrite misses.
- Leukocytes (white blood cells) in urine — the microscopic count; more than 10 per high-power field confirms inflammation and raises the chance that a negative nitrite is a false negative.
- Bacteria on microscopy and urine culture — the culture is the reference test; it reports the organism, the count (usually 100,000 colony-forming units per mL, or lower in symptomatic people) and antibiotic sensitivities.
- Urine pH — a pH above 8 with positive nitrite suggests Proteus or another urea-splitting organism and a possible struvite stone.
- Blood in urine — common with cystitis; blood that persists after treatment needs its own evaluation.
- Squamous epithelial cells — many squamous cells mean contamination, which can produce a false-positive nitrite in an old sample.
- Urine specific gravity — very dilute urine (below 1.005) lowers nitrite concentration and makes a false negative more likely.
- Neutrophils, CRP and creatinine in blood — checked when fever or flank pain suggests the infection has reached the kidney.
What usually happens next
- If you have typical bladder symptoms and a positive nitrite, most clinicians will start treatment and send a culture, which takes 24 to 72 hours; the antibiotic may be changed when the sensitivities come back.
- If nitrite is negative but you have symptoms and white cells, the culture still decides; many clinicians treat a symptomatic woman with pyuria while waiting, since enterococcus and staphylococcus do not make nitrite.
- If nitrite is positive but you have no symptoms, expect a question about when the sample was collected and whether it was a clean catch; a repeat first-morning sample often settles it, and treatment is usually not needed outside pregnancy.
- In pregnancy, a positive nitrite is followed by a culture and treated if confirmed, because untreated bacteria in pregnancy raise the risk of kidney infection and preterm birth; screening in pregnancy uses the culture rather than the dipstick because the dipstick misses too many.
- Recurrent positive results (three or more infections a year) lead to a discussion of prevention: fluids, post-menopausal vaginal estrogen, cranberry, and in some cases prophylactic antibiotics or methenamine.
- Ask: how long had the urine been in my bladder, was this a clean catch, was leukocyte esterase positive, is a culture pending, and am I taking vitamin C or phenazopyridine?
Diet, lifestyle and natural levers with evidence
What can move Nitrite in urine once the cause is known. Nothing here replaces finding the cause.
Test the first urine of the morning
Strong evidenceThis changes the result more than any supplement. Nitrite needs about four hours of bladder dwell time to accumulate, so a first-morning sample roughly doubles the sensitivity compared with a random sample passed shortly after the previous void. Studies of dipstick accuracy report sensitivities as low as 20 to 30 percent in random daytime samples and 50 to 70 percent in first-morning or 4-hour-held samples. Test within two hours of collection or refrigerate.
Drink more water to prevent recurrent infections
Moderate evidenceIn a randomised trial of 140 premenopausal women with recurrent cystitis who drank little, adding 1.5 liters of water a day halved infections over a year (1.7 versus 3.2 episodes) and antibiotic use. Frequent voiding flushes bacteria before they multiply to the counts that produce nitrite.
Do not load fluids just before a test; dilute urine and short dwell time cause false negatives. People with heart or kidney failure should check before increasing intake.
Cranberry products for recurrent UTI
Moderate evidenceA 2023 Cochrane review of 50 trials found cranberry juice or capsules reduced symptomatic culture-confirmed UTIs by about a quarter in women with recurrent infections and by about half in children, with no clear benefit in older people in care homes or people with catheters. Proanthocyanidins prevent E. coli, the main nitrite producer, from binding to the bladder lining; about 36 mg a day was used.
Prevention only. Sweetened juice is high in sugar, and cranberry can increase the effect of warfarin.
Stop high-dose vitamin C before testing
Moderate evidenceAscorbic acid in urine interferes with the Griess reaction and with the blood, glucose and leukocyte esterase pads, producing false-negative nitrite results at urine concentrations reached with supplements of 500 mg or more a day. In laboratory studies, 25 mg/dL of ascorbic acid in urine abolished the nitrite reaction on several brands of strip. Pause supplements for 24 hours before a urine test if practical, or tell the lab.
Vitamin C does not prevent or treat UTIs; trials of ascorbic acid for UTI prevention have been small and inconsistent.
D-mannose
Preliminary evidenceAn early 6-month trial of 308 women found 2 g of D-mannose daily reduced recurrent UTI from 60 to 15 percent, but a larger 2024 placebo-controlled trial of 598 women in general practice found no significant benefit (51 versus 56 percent had a further infection). It is thought to block E. coli adhesion, but the evidence is mixed.
Loose stools at higher doses; it is a sugar and may slightly affect glucose readings in diabetes.
When to see a clinician promptly
- Positive nitrite with fever above 100.4°F (38°C), shaking chills, flank or back pain, vomiting or confusion: possible kidney infection or sepsis, needs same-day assessment and emergency care if you feel faint, are breathing fast or cannot keep fluids down.
- Positive nitrite or urinary symptoms in pregnancy, in a man, in a child, or in anyone with diabetes, a kidney transplant, a single kidney, kidney stones or a weakened immune system.
- Symptoms that are not improving after 48 hours of antibiotics, or that return within two weeks of finishing a course.
- Blood in the urine with a positive nitrite, especially if it persists after the infection is treated or you are over 40.
- Severe one-sided pain spreading to the groin with a positive nitrite, or inability to pass urine: a possible obstructed, infected kidney is an emergency.
- Three or more infections in a year, to discuss investigation and prevention.
Frequently asked questions
What does nitrite in urine mean?
It means bacteria that convert nitrate to nitrite, most often E. coli, were growing in your urine, which usually indicates a urinary tract infection. The normal result is negative. A positive result is about 95 percent specific, so with symptoms such as burning and frequency it is strong evidence of a bacterial infection. Without symptoms it may be harmless bacteria colonising the bladder, or a sample that sat too long before testing.
Can you have a UTI with negative nitrite?
Yes, frequently. The nitrite test misses about half of culture-proven infections. Enterococcus, Staphylococcus saprophyticus, pseudomonas and group B strep do not produce nitrite at all; urine that has been in the bladder for under four hours has not accumulated enough; and dilute urine, vitamin C and low dietary nitrate all mask it. If you have symptoms and white cells in the urine, a negative nitrite does not rule out infection and a culture is the next step.
What does nitrite negative but leukocytes positive mean?
It is the most common pattern in real infections that the nitrite test misses, so it is often still a UTI, particularly with enterococcus or staphylococcus, or when the urine was passed soon after the previous void. It can also mean inflammation from another cause: chlamydia or another STI, a kidney stone, interstitial cystitis, prostatitis, a recently treated infection or a contaminated sample. Symptoms and the urine culture settle it.
What does nitrite positive but leukocytes negative mean?
Usually one of three things: an early infection before white cells have arrived in numbers, an old sample in which white cells broke down while bacteria multiplied, or a false-negative leukocyte pad from vitamin C, high glucose or certain antibiotics. With symptoms it is treated as a probable UTI; without symptoms a fresh first-morning clean-catch sample is the best next test.
Is nitrite in urine during pregnancy dangerous?
It needs prompt follow-up but is not an emergency on its own. Bacteria in the urine during pregnancy, with or without symptoms, raise the risk of kidney infection, low birth weight and preterm birth, so a positive nitrite is confirmed with a culture and treated with a pregnancy-safe antibiotic, with a repeat culture afterwards. Fever, back pain, vomiting or contractions with a positive nitrite need same-day assessment.
Can dehydration or diet cause nitrite in urine?
No. Nitrite is made only by bacteria. Dehydration concentrates urine and can make it cloudy or dark but does not produce nitrite, and dietary nitrate from vegetables is the raw material, not the product. A diet very low in nitrate can, however, cause a false negative in someone who does have an infection. The only diet-related false positive is pigment from beetroot or similar foods discolouring the pad.
How accurate is a home urine nitrite test?
Home strips use the same chemistry as the lab and are about as specific, so a clear positive with symptoms is meaningful. They share the same low sensitivity, so a negative does not rule out infection. Home kits are more prone to false positives from strips stored in humid bathrooms or past their expiry date, and false negatives from testing a random afternoon sample. Use a first-morning sample, read at exactly the time stated and confirm with your clinician before taking antibiotics.
Should a positive nitrite be treated if I have no symptoms?
Usually not. Bacteria in the bladder without symptoms (asymptomatic bacteriuria) are common in older adults, people with diabetes and anyone with a catheter, and treating them does not reduce infections or deaths and increases antibiotic resistance. The exceptions, where it is treated, are pregnancy and the days before surgery or a scope on the urinary tract. A repeat clean-catch sample is the usual next step.
References
- Urinalysis. MedlinePlus, US National Library of Medicine (2023)View source
- Urinalysis. Mayo Clinic (2023)View source
- Urinalysis. Merck Manual Professional Version (2024)
- Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. American Family Physician (2005)
- Devillé WL, Yzermans JC, van Duijn NP, Bezemer PD, van der Windt DA, Bouter LM. The urine dipstick test useful to rule out infections: a meta-analysis of the accuracy. BMC Urology (2004)
- Bent S, Nallamothu BK, Simel DL, Fihn SD, Saint S. Does this woman have an acute uncomplicated urinary tract infection?. JAMA (2002)
- 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. Clinical Infectious Diseases (2019)
- Gupta K, Hooton TM, Naber KG, et al.. International clinical practice guidelines for the treatment of acute uncomplicated cystitis and pyelonephritis in women: a 2010 update by the Infectious Diseases Society of America and the European Society for Microbiology and Infectious Diseases. Clinical Infectious Diseases (2011)
- Owens DK, Davidson KW, Krist AH, et al.. Screening for asymptomatic bacteriuria in adults: US Preventive Services Task Force recommendation statement. JAMA (2019)
- Hooton TM, Vecchio M, Iroz A, et al.. Effect of increased daily water intake in premenopausal women with recurrent urinary tract infections: a randomized clinical trial. JAMA Internal Medicine (2018)
- Williams G, Hahn D, Stephens JH, Craig JC, Hodson EM. Cranberries for preventing urinary tract infections. Cochrane Database of Systematic Reviews (2023)
- Hayward G, Mort S, Hay AD, et al.. D-mannose for prevention of recurrent urinary tract infection among women: a randomized clinical trial. JAMA Internal Medicine (2024)
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Ask about my Nitrite in urineThis page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.