Urine Nitrites (NIT): Bacterial Marker

What are urine nitrites

Nitrites (NIT) are substances that are normally not detected in urine. Their presence indicates that certain bacteria are in the urine, converting nitrates (naturally present in urine) into nitrites.

This marker is part of a routine urinalysis (dipstick test) and is considered one of the fastest ways to suspect a urinary tract infection. The result is reported as negative (normal) or positive.

Reference ranges

Normal result: negative. Any positive nitrite result requires attention and usually indicates a bacterial urinary tract infection.

It is important to understand that a negative result does not guarantee the absence of infection — some bacteria do not convert nitrates to nitrites.

Why urine nitrites may be positive

A positive nitrite result is most commonly associated with a bacterial infection:

• Urinary tract infection (UTI) — the most common cause. Bacteria, especially *Escherichia coli* (responsible for about 80% of UTIs), convert urinary nitrates to nitrites.
• Asymptomatic bacteriuria — bacteria are found in the urine, but the person has no symptoms. More common in pregnant women and older adults.
• Pyelonephritis — kidney infection, which can also cause a positive nitrite result.

Positive nitrites together with positive leukocytes in urine strongly increase the likelihood of a UTI.

Why the result may be falsely negative

It is important to know that a negative nitrite result does not mean there is definitely no infection:

• Gram-positive bacteria (e.g., *Enterococcus*, *Staphylococcus*) do not reduce nitrates to nitrites.
• Insufficient time in the bladder — bacteria need at least 4 hours to convert nitrates to nitrites. If urine is collected shortly after the last voiding, the result may be falsely negative.
• Low-nitrate diet — if the diet is low in nitrates (few vegetables), there will be less substrate for bacteria.
• Very dilute urine — excessive fluid intake can reduce nitrite concentration.

Therefore, laboratories often recommend testing morning urine (which has been in the bladder longer).

What to do next

1. If nitrites are positive — see your doctor. A urine culture is usually ordered to identify the specific bacterium and its antibiotic sensitivity. 2. Evaluate together with urine leukocytes (LEU) — both positive results strongly suggest a UTI. 3. Pay attention to symptoms: burning, frequent urination, fever, back pain. 4. Drink adequate fluids — this supports urinary tract hygiene. 5. For pregnant women, even asymptomatic bacteriuria requires treatment — be sure to inform your doctor.

Monitoring over time

After treatment, it is important to repeat the urine test to confirm that the infection has been cured. Recurrent UTIs (3 or more per year) require further investigation.

The QbiLabs platform allows you to track urine test results alongside other markers and detect recurrent infections.

Questions for your doctor

• Urine nitrites are positive — is a urine culture needed?
• Could I have an infection even if nitrites are negative?
• I have recurrent urinary tract infections — what additional tests are recommended?
• Does asymptomatic bacteriuria need to be treated in my case?
• How can I reduce the risk of recurrent UTIs?

*This is not medical advice. Consult your doctor for health-related decisions.*