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What are Nitrites in Urine?

Nitrites in urine are chemical compounds that can indicate the presence of certain bacteria in the urinary tract, most commonly pointing to a urinary tract infection (UTI). A positive nitrite test means that bacteria capable of converting nitrates to nitrites are present in your urinary system, and it is often used alongside other urinalysis markers to diagnose infection.

Understanding Nitrites in Urine

Normally, urine contains nitrates—harmless byproducts from dietary sources like leafy greens and beets. Some bacteria, particularly gram-negative species, produce the enzyme nitrate reductase, which converts nitrates to nitrites. This conversion usually takes several hours of urine being retained in the bladder, which is why first-morning urine often yields the most accurate nitrite results.

Common nitrite-producing bacteria include:

  • Escherichia coli (E. coli) – causes 80–90% of UTIs
  • Klebsiella species
  • Proteus species
  • Enterobacter species
  • Citrobacter species

Normal Ranges and Test Interpretation

  • Normal: Negative (no nitrites detected)
  • Abnormal: Positive (nitrites present)

A positive nitrite test has high specificity (90–100%) for certain UTIs, but a negative result doesn’t completely rule out infection. Reasons for a false negative include:

  • Infection by non–nitrite-producing bacteria (e.g., Enterococcus, Staphylococcus)
  • Urine in bladder for less than 4 hours
  • Low dietary nitrate intake
  • Very dilute urine from high fluid intake
  • Interference from high vitamin C intake

Clinical Significance and Symptoms

Positive nitrites in urine usually indicate bacteriuria and often a UTI, especially if symptoms are present:

  • Burning or pain during urination
  • Frequent or urgent need to urinate
  • Cloudy or foul-smelling urine
  • Pelvic discomfort (women)
  • Visible blood in urine
  • Fever or chills (possible kidney involvement)

In certain groups—like pregnant women, immunocompromised patients, or those scheduled for urologic procedures—positive nitrites may warrant treatment even without symptoms.

Special Considerations

  • Pregnancy: UTIs can lead to complications like preterm labor and low birth weight—prompt treatment is essential.
  • Elderly: May not show classic UTI symptoms despite positive nitrites; screening is often recommended if other signs of illness are present.

Prevention and Management

If nitrites are present, your provider will typically confirm with a urine culture and prescribe antibiotics targeted to the bacteria found. To reduce recurrence risk:

  • Stay well-hydrated and urinate regularly
  • Empty your bladder fully when urinating
  • Wipe front to back to prevent bacterial spread
  • Urinate after sexual activity
  • Avoid irritating hygiene products in the genital area
  • Discuss cranberry products or D-mannose with your provider if prone to UTIs

Always finish the full course of prescribed antibiotics and follow up as advised, especially for complicated or recurrent infections.

DISCLAIMER: A positive nitrite test should be interpreted in the context of other urinalysis results and your symptoms. Consult a healthcare provider for diagnosis and treatment recommendations.