What Causes Nitrites in Urine? (2024)

Almost everyone eats a diet that includes nitrates. These compounds are found naturally in vegetables and are also added to foods like processed meats to help preserve them. Most of the time, nitrates pass through our bodies without causing problems.

Bacteria can turn nitrates into similar compounds called nitrites, which are then excreted in urine. For this reason, healthcare providers will sometimes use urine dipstick testing for nitrites to diagnose urinary tract infections (UTIs).

Read on to learn how nitrates turn into nitrites and whether nitrites are an accurate sign of a UTI.

What Causes Nitrites in Urine?

Nitrates enter our bodies through the foods we eat. You may have heard that processed meats are a major source of nitrates, but in reality, up to 85% of our nitrate intake comes from vegetables such as spinach, carrots, and celery.

About 25% of the nitrates you consume are transformed into nitrites by bacteria. Some types of bacteria are linked to higher levels of nitrite production than others. This includes Escherichia coli, (E. coli) a type of bacteria that causes roughly 70% of all UTIs.

Most of the nitrites that form—about 75%—leave your body through urine. The rest get reabsorbed into your blood and tissues. Because of the role bacteria plays in transforming nitrates into nitrites, the nitrite levels in your urine are sometimes used to help diagnose bacterial infections, specifically in the urinary tract.

Symptoms of a Urinary Tract Infection

UTIs are the second most common type of infection in the body (after the common cold). Caused by bacteria entering through the urethra or growing in some part of the urinary tract, these infections are usually minor but can become severe.

Symptoms of UTIs include:

• Pain or burning with urination
• Fever
• Shakiness
• Fatigue
• A frequent urge to urinate
• A feeling of pressure in your lower abdomen
• Cloudy or foul-smelling urine

Why Do Healthcare Providers Test for Nitrites in Urine?

A dipstick urinalysis test is easy and offers immediate results, so your healthcare provider may use one to check for nitrites—especially if a UTI is already suspected. A test strip will be dipped into your urine sample; it changes color based on the chemicals found in your urine.

This method of testing for a UTI does have its limitations, however, since nitrites give little information about what type of bacteria is causing the infection. It's also possible to have a UTI without having nitrites in your urine.

The presence of nitrites in your urine can help your provider determine whether more testing is needed. For example, a urinary culture will provide more accurate and thorough results but has to be sent off to a lab, which can take a few days.

What to Expect During Urinalysis

If your healthcare provider orders a urinalysis, you will be asked to provide a urine sample in a sterile container. Because nitrite testing is more accurate the longer your urine has been in your bladder, you may be asked to arrive at the office with a full bladder.

The results of a dipstick test will be available right away; your provider may also send your urine to be analyzed under a microscope.

Treatment for Nitrites in Urine

If your nitrite test comes back positive and your healthcare provider determines you have a mild UTI, you'll likely be prescribed a short course of broad-spectrum antibiotics such as trimethoprim-sulfamethoxazole (TMP-SMX) that you'd take for around three days.

Your symptoms should begin to improve within a few days of starting treatment. Be sure to take all your antibiotics, even if you're feeling better.

A more complicated UTI might require a longer course of antibiotics that could take up to two weeks or be given intravenously. Your provider will likely order additional testing to figure out which strain of bacteria you have. This information will allow them to prescribe a more targeted antibiotic.

Complications and Warning Signs

In most cases, a simple course of antibiotics will resolve a UTI. But some people will develop complicated infections that develop outside of the urinary tract, like the kidneys. These UTIs don't respond well to standard treatments. Symptoms include severe abdominal or lower back pain, confusion, and fever.

Complications of a urinary tract infection can include:

• Cystitis
• Urethritis
• Pyelonephritis
• Sepsis

Summary

Nitrites can form naturally in your body when the foods you eat are digested. However, some types of bacteria increase the amount of nitrites you pass through your urine. Testing urine for nitrites is a quick way to screen for a UTI, but other tests like urine cultures can provide more detailed and accurate information.

A Word From Verywell

If you are experiencing pain when urinating or have a frequent urge to go, talk to your healthcare provider about getting screened for a UTI. Dipstick testing for nitrites can provide quick answers, but your provider may also order other tests to make sure you get the best type of antibiotic for your specific infection.

Early diagnosis and treatment of a UTI can help you avoid severe complications like a kidney infection or sepsis.