Nitrites in Urine: What Does a Positive or Negative Result Mean?

Nitrites in urine usually mean there are bacteria in the urinary tract that can cause an infection. Many of these bacteria turn nitrates, a normal part of urine, into nitrites, which a dipstick can detect. A positive result makes a urinary tract infection (UTI) likely, but symptoms, the rest of the urine test and sometimes a urine culture are needed to decide what it means for you.

Nitrites are not normally found in urine, so a normal result is negative. Reports usually show nitrite simply as positive or negative rather than as a number, and Cleveland Clinic gives negative as its reference. Methods and report formats vary between laboratories, so check the range printed on your own report and ask if anything is unclear.

This guide covers how to read a positive or negative nitrite result. Blood and white cells on the same dipstick are covered in separate guides.

Seek urgent medical advice through local services if a positive result comes with any of the following. The NHS notes that some of these can signal a kidney infection, which can lead to sepsis if untreated.

• Confusion, drowsiness or difficulty speaking: call emergency services or go to an emergency department now.
• A very high or low temperature, feeling hot and cold, or shivering.
• Pain in the back just under the ribs, or lower tummy pain.
• Blood in the urine that looks pink, red or dark brown.
• Symptoms that get worse quickly or do not improve within 48 hours of starting treatment.
• Any suspected UTI in pregnancy, in a man, in a child, or in someone aged 65 or older.

A positive nitrite is one of the stronger dipstick signs of infection. In UK primary care guidance for women under 65 with urinary symptoms, a positive nitrite on its own is enough to make a UTI likely. The same guidance cites a study in men in which a positive nitrite was usually confirmed by culture.

It is still a screening test. Home kits in particular can be quick but unreliable, and MedlinePlus notes that a provider may still need to order lab tests. Sample handling also matters: UK guidance advises that urine for culture is tested within 4 hours of collection or kept refrigerated or preserved, so ask how your sample was stored if the result seems unexpected.

Yes. MedlinePlus explains that some types of bacteria do not change nitrates into nitrites, so the test can be negative even when infection is present. UK guidance also states that a negative nitrite result does not exclude a UTI.

Timing can play a part too. Conversion takes time, which is why labs often ask for urine that has been in the bladder for a few hours; MedlinePlus advises collecting a culture sample after 2 to 3 hours where possible. Very frequent urination, which is common with a UTI, may leave less time.

This is why clinicians look at the whole picture. White cells (leukocytes) in the urine and your symptoms are considered alongside the nitrite. For women under 65 with symptoms, UK guidance recommends sending urine for culture when leukocytes are positive but nitrite is negative.

Not always. Bacteria in the urine without symptoms is called asymptomatic bacteriuria. UK guidance advises against routinely treating it in non-pregnant women, because treatment does not reduce illness or death and may cause harm. Screening and treatment are not recommended in older adults either, and most people with a long-term urinary catheter will have bacteria in their urine.

Pregnancy is an important exception. Guidance recommends sending urine for culture in pregnancy, including when there are no symptoms. If you are pregnant, tell the clinician straight away. Symptoms that are easy to overlook, such as new confusion in an older relative, should also be reported rather than assumed to be nothing.

A dipstick shows chemical signs; a culture grows any bacteria or yeast from the sample in a lab. It shows which germ is present and roughly how much, and further testing can show which antibiotics are likely to work. MedlinePlus says culture results usually take 24 to 48 hours.

UK guidance recommends culture in several situations, including:

• Pregnancy, with or without symptoms.
• Suspected UTI in men.
• Symptoms that persist or come back after antibiotics.
• Recurrent UTIs, meaning 2 in 6 months or 3 in 12 months.
• Suspected kidney infection or sepsis.
• People with a urinary catheter when antibiotics are prescribed.

A clean-catch, midstream sample lowers the chance of contamination. Wash and dry your hands, avoid touching the inside of the container, pass the first part of the stream into the toilet and collect the middle part. UK guidance notes that antiseptic cleansing before collection is not recommended because it may stop bacteria from growing.

Tell the clinician about medicines and supplements you take, and about a period or bleeding haemorrhoids, since these can affect urine results. Do not stop any prescribed medicine unless you are told to.

Bring the full report and use these questions to understand the plan.

• Was the nitrite result from a home kit, a clinic dipstick or a lab test?
• Has a urine culture been sent, and when and how will I get the result?
• If I have no symptoms, do I need treatment, or is watching enough?
• If the nitrite was negative, what else makes you think I do or do not have an infection?
• Which symptoms mean I should seek care before the culture result arrives?
• If this keeps happening, what further assessment would you consider?

On SameCase, patients and verified doctors share de-identified cases. Reading how others with a similar urine result described their symptoms, sample collection and culture follow-up can help you spot details worth mentioning and shape your questions. Similar cases cannot tell you what your own result means. Use them to prepare, then discuss your questions with the clinician who has your full results.