30 October 20269 min read

Nitrites in Urine: What a Positive Test Means

Medical Review

Medically Reviewed by Dr. Pedro Yelamo Vera, MD

Licensed Physician No. 484814280 · Official Medical College of Bizkaia (Spain)Last reviewed: 31 October 2026

Nitrites in urine usually point to bacteria in the bladder. What a positive or negative result means, when you need a culture and when to see a doctor.

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Nitrites in urine usually mean bacteria are growing in your urinary tract. Many common germs turn nitrates, a normal part of urine, into nitrites. With symptoms such as burning or needing to pee often, a positive result makes a urinary tract infection (UTI) likely. A negative result does not rule one out.

TL;DR

Nitrites are not normally found in urine. A positive result usually points to bacteria.
With UTI symptoms, positive nitrites make an infection likely.
Negative nitrites do not rule out a UTI. Some germs do not make nitrites.
Bacteria with no symptoms are often left untreated, except in pregnancy.
In the UK, dipsticks are not used for people over 65 or with a catheter.
Fever, back pain under the ribs or vomiting with a positive test: see a doctor today.

Dr. Pedro Yelamo Vera is a GP licensed in Spain (Colegiado No. 484814280).

For a medical emergency, call 112 or go to the nearest local emergency department. Do not wait for a video consultation or an online reply.

What do nitrites in urine mean?

Your urine normally contains nitrates. MedlinePlus explains that some bacteria that cause UTIs change nitrates into nitrites. So nitrites in a urine sample usually mean bacteria are present. Healthy urine should show none.

There is no "normal level" to compare. The result is simply positive or negative. On a Spanish report, look for nitritos in the urine strip section, often called sistemático de orina or tira reactiva. It will say positivo or negativo. A UK dipstick and a US urinalysis (UA) show it the same way.

Does a positive nitrite test mean I have a UTI?

Usually, if you also have symptoms. The NHS lists the main ones:

Pain or burning when you pee.
Needing to pee more often than usual.
Cloudy pee.
Pain in the lower tummy, or in the back just under the ribs.
A high temperature, or feeling hot, cold and shivery.

UK guidance for GPs (UKHSA) says a positive nitrite test makes a UTI likely in women under 65 with symptoms. In men, it also points strongly to infection. One study it quotes found that 96% of positive nitrite tests in men were confirmed by a urine culture.

Without symptoms, the picture changes. Bacteria in urine with no symptoms is called asymptomatic bacteriuria. It becomes more common with age. UK guidance says it should not be treated routinely in women who are not pregnant, because treatment does not help and may cause harm.

Can I have a UTI if my nitrites are negative?

Yes. MedlinePlus is clear that you may still have an infection even when no nitrites are found. There are two main reasons:

Some bacteria do not make nitrites. The test cannot see them.
The urine was not in the bladder long enough. UKHSA notes that some bacteria need four hours or more to make nitrites. A first morning sample is more reliable. With a UTI you pee often, so a daytime sample may test negative.

A study UKHSA quotes found that nitrites picked up only about half of the infections in men. That is why a doctor looks at your symptoms, not only the strip.

What if nitrites and leukocytes are both on my result?

The same strip usually tests for leukocytes, or white blood cells. On a Spanish report you may see leucocitos or esterasa leucocitaria. UKHSA reads the two together for women under 65 with symptoms:

Nitrites positive: a UTI is likely.
Leukocytes and blood positive, nitrites negative: a UTI is also likely.
Leukocytes positive only: a UTI is as likely as another cause. A urine culture helps.
All negative: a UTI is less likely.

Other problems can cause similar symptoms. UKHSA says 75% to 80% of people with vaginal discharge do not have a UTI. Thrush, a sexually transmitted infection or menopause changes may be the cause instead.

Got a urine or blood test result and not sure what it means?

You can book a video visit with a GP licensed in Spain, in English or Spanish. He reads your whole report, asks about your symptoms, and explains what should happen next.

Get your test results reviewed

How do Spain, the UK and the US use this test?

The test is the same everywhere. How doctors use it differs a little.

Spain: a urine test often comes with routine blood tests. The report has the strip results and sometimes a microscope check, the sedimento. If an infection is likely, the doctor may ask for a urine culture, called urocultivo. In pregnancy, the Spanish obstetrics society (SEGO) advises a urine culture in the first trimester for every woman.
UK: GPs follow UKHSA tools. They do not use dipsticks for people over 65 or with a catheter, because bacteria without infection are so common there. Men with a suspected UTI should have a urine culture before antibiotics.
US: nitrites appear on a standard urinalysis. MedlinePlus says a provider may add a urine culture if you have UTI signs. Culture results usually take a couple of days.

A urine culture shows which germ is growing and which antibiotics work against it. Collect the sample with the "clean catch" method your clinic explains. It keeps the result reliable.

What about pregnancy and children?

Pregnancy: any bacteria in urine matter, even without symptoms. A Spanish health ministry bulletin, reproducing the SEGO protocol, says 20% to 40% of untreated cases progress to a kidney infection. UKHSA says pregnant women with bacteria in their urine should always be offered antibiotics, with a urine culture. If you are pregnant and have a positive nitrite test, speak to a doctor today.

Children: the NHS says a child with a UTI may have a fever, seem generally unwell, feed poorly, vomit or start wetting again. Spanish paediatric guidance (AEPap) notes that strips are less reliable under the age of two. If a UTI is suspected, a negative strip does not rule it out and a urine culture is advised. A child with a fever and a positive test should see a doctor today.

What happens next?

Positive nitrites and typical symptoms: a doctor confirms the diagnosis and decides on treatment. You can read more on our UTI care page.
Positive nitrites, no symptoms, not pregnant: often no treatment is needed. The doctor decides with your full history.
Negative nitrites but clear symptoms: you may still need care. A urine culture can settle it.
Symptoms that are not better within 48 hours of treatment: the NHS advises an urgent check.

See a doctor today, without waiting, if you have a positive test and any of these: a high temperature or shivering, a temperature below 36 °C, pain in your back just under the ribs, blood in your pee, or being sick. The same applies if you are pregnant, a man, over 65, have diabetes or a weak immune system, or for a child.

Call 112 if someone is confused, very drowsy or has trouble speaking.

Talking it through with a doctor by video

Dr. Yelamo is a GP licensed in Spain. He sees adults, children and pregnant patients by video, every day from 07:30 to 20:30 (Spain time). In the visit he will:

Read your full urine report, including nitrites, leukocytes and blood.
Ask about your symptoms, pregnancy, medicines and past infections.
Explain whether you need a urine culture or a repeat test.
Tell you clearly if you need an in-person check instead.

He does not promise any test or prescription before the visit. Where clinically appropriate, following a genuine evaluation. Treatment and prescriptions are issued solely at the doctor's discretion based on evidence-based clinical guidelines.

A prescription is never guaranteed: it is issued only where clinically appropriate after a genuine evaluation, as a private electronic prescription under Spanish law. This service is for urgent, non-emergency care. In an emergency, call 112.

See how the Urgent Care video visit works. It lasts 15 minutes and costs €50.

This guide is general information. It does not replace a consultation with your doctor.

Frequently asked questions

What does nitrite positive in urine mean?

It usually means bacteria are in your urine. With symptoms such as burning or needing to pee often, a UTI is likely.

Can you have a UTI with negative nitrites?

Yes. Some bacteria do not make nitrites, and urine that has not stayed in the bladder for a few hours can test negative.

Is a positive nitrite test always an infection?

Not always. Bacteria with no symptoms are common, especially in older people. Outside pregnancy they are often left untreated.

What is the normal level of nitrites in urine?

There is no level. Healthy urine has no nitrites, so the result is simply positive or negative.

What is nitritos on a Spanish urine test?

It is the Spanish word for nitrites. It appears in the strip section of the report, marked positivo or negativo.

I am pregnant and my nitrites are positive. What should I do?

Speak to a doctor today. In pregnancy, bacteria in urine are checked with a urine culture and usually treated, even without symptoms.

Sources

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Medical Citations & Sources

This content is written and reviewed by a licensed physician with reference to the following official health authorities.