How to Read UTI Test Strip Results: Leukocytes and Nitrite Explained

Knowing how to read UTI test strip results takes the guesswork out of a stressful moment: you have symptoms, you have a strip, and you want to know what the colors mean. This guide walks you through collecting a good sample, reading the leukocyte and nitrite pads at the right time, understanding each combination of results, and knowing when to call your doctor.

What a UTI test strip checks

At-home UTI screening relies on two test pads:

• Leukocytes (leukocyte esterase). This pad detects an enzyme released by white blood cells. Your body sends white blood cells to fight infection, so a positive result suggests inflammation somewhere in the urinary tract.
• Nitrite. Many bacteria that cause UTIs, including E. coli, turn natural nitrates in urine into nitrites. A positive nitrite pad suggests those bacteria are present.

Multi-marker strips such as our URS 9-in-1 and URS 10-in-1 include both pads, plus others like protein and pH that can add useful context.

Before you test: get an accurate sample

Good results start with a good sample:

1. Use first-morning urine if you can. Urine needs to sit in the bladder for about 4 hours for bacteria to produce enough nitrite to detect.
2. Don't drink lots of water right before testing. Very dilute urine can hide a positive result.
3. Collect a clean, midstream sample. Wash your hands, clean the genital area, let the first bit of urine go into the toilet, then catch the middle portion in a clean, dry cup.
4. Test right away. Urine left sitting out can give false results.

How to read UTI test strip results step by step

1. Dip the strip so every pad is covered, then remove it right away.
2. Tap off the extra urine on the edge of the cup and hold the strip level.
3. Start a timer as soon as the strip comes out of the sample.
4. Read the nitrite pad at about 60 seconds. Any pink color, even a faint one, counts as positive. Compare it to the chart.
5. Read the leukocyte pad at about 2 minutes. This pad develops more slowly. Its color moves from beige toward purple as the level rises, usually shown on the chart as negative, trace, small (+), moderate (++) or large (+++).
6. Read in good light and hold the strip right next to the color chart. Always use the exact reading times printed on your kit's chart.

Reading too early can make a positive look negative. Reading too late can make colors darker than they should be, so timing matters.

What your UTI test strip results mean

Leukocytes positive and nitrite positive

This is the result most strongly linked with a bacterial UTI. If you also have symptoms such as burning, urgency or frequent urination, contact your doctor. You will likely need antibiotics, which only a healthcare provider can prescribe.

Leukocytes positive, nitrite negative

You may still have a UTI. Some bacteria, such as Enterococcus and Staphylococcus saprophyticus, don't make nitrite, and urine that hasn't been in the bladder long enough may not show it. White blood cells can also come from other inflammation or from a contaminated sample. If you have symptoms, call your doctor.

Leukocytes negative, nitrite positive

This can be an early infection, before many white blood cells have arrived. It can also come from a sample that sat out too long. Retest with a fresh first-morning sample and call your doctor if you have symptoms.

Both negative

A UTI is less likely, but a negative strip doesn't completely rule one out. If your symptoms are strong or don't go away, see a healthcare provider anyway. Your symptoms matter more than the strip.

Other pads that add context

• Blood: Small amounts of blood are common with bladder infections, but blood can also have other causes and should be checked by a doctor.
• Protein: A mild rise can happen during an infection. Learn more in our guide to protein in urine causes.
• pH: Some bacteria make urine more alkaline, so a high pH alongside positive leukocytes or nitrite adds to the picture.
• Specific gravity: A low reading means dilute urine, which can weaken a positive result.

Common reasons for a misleading result

• Diluted urine from drinking a lot of fluid can cause a false negative.
• High doses of vitamin C can block the nitrite and leukocyte reactions.
• Recent antibiotics can lower readings even if an infection is not fully treated.
• Urinary pain relievers containing phenazopyridine (such as AZO) turn urine orange and can interfere with the color reading. Test before you take them.
• Contamination from vaginal discharge or an unclean cup can cause a false positive leukocyte result.
• Expired or damp strips may not react properly. Keep the container sealed.

When to see a doctor

A test strip helps you decide how quickly to act, but it can't replace medical care. Contact a healthcare provider if:

• You have UTI symptoms and a positive leukocyte or nitrite result.
• You have fever, chills, nausea or pain in your back or side. These can be signs of a kidney infection and need prompt care.
• You see blood in your urine.
• You are pregnant, male, or testing a child, since UTIs in these groups always need medical evaluation.
• You get UTIs often, or your symptoms return after treatment.

Your doctor may order a urine culture to identify the exact bacteria and choose the right antibiotic.

Key takeaways on how to read UTI test strip results

• Test first-morning, midstream urine and read it right away.
• Read nitrite at about 60 seconds (any pink is positive) and leukocytes at about 2 minutes.
• Both pads positive strongly suggests a UTI. One positive pad is still worth acting on if you have symptoms.
• A negative strip doesn't override real symptoms. When in doubt, call your doctor.

Keep a pack of URS 9-in-1 Urine Test Strips at home so you can check quickly at the first sign of symptoms.

This article is for general information and is not medical advice. At-home test strips are screening tools and do not diagnose infection. Talk to a healthcare professional about your symptoms and results.