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Blood Test Tracker

Urine Blood (Dipstick)

A dipstick check for blood in your urine. It reacts to red blood cells, hemoglobin and myoglobin, so a positive result is usually followed by a microscope check.

AI-verified against cited sources. Awaiting expert reviewAlso called BLDLOINC 5794-3

What it is

This urine dipstick pad changes color when it meets heme, the iron-containing part of hemoglobin. Heme can come from intact red blood cells, from free hemoglobin released when red cells break open, or from myoglobin released by muscle. Most urine has none, so the usual result is negative. Results are reported as negative, trace, or by amount (small, moderate, large, or 1+ to 3+). The strip can't tell which source the heme came from, so a positive result is often followed by a look under the microscope.

Why it matters

Blood in the urine is called hematuria. It has many causes. Many are harmless or short-lived, such as hard exercise, menstrual blood in the sample, sexual activity, some medicines or a urinary tract infection. Less often it's linked to kidney stones, an enlarged prostate, kidney disease or, rarely, a tumor of the urinary tract. Because the causes vary so much, clinicians look at the dipstick, a microscope check of the urine, your age, your symptoms and your risk factors together. Guidelines define microscopic hematuria by the number of red blood cells seen under the microscope, not by the dipstick.

If it’s high

A positive result means the strip reacted to heme in your urine. That can be from red blood cells, or from hemoglobin or myoglobin without intact cells. The cause is often harmless or short-lived, and the strip can read positive from things like menstrual blood in the sample. A microscope check of the urine, which counts red blood cells, helps show what's going on. Visible blood in the urine, or a positive result that keeps coming back, is worth discussing with a clinician.

Common causes

  • Menstrual blood or vaginal bleeding getting into the sample
  • Hard exercise, especially long-distance running
  • Sexual activity
  • A urinary tract infection or irritation of the bladder or kidney
  • Kidney stones
  • Some medicines, such as blood thinners
  • An enlarged prostate
  • Hemoglobin or myoglobin in the urine from the breakdown of red blood cells or muscle injury, which can turn the strip positive without many red cells under the microscope
  • Kidney conditions that affect the filters (glomerular disease), such as IgA nephropathy
  • Rarely, tumors of the kidney, bladder or prostate

What can help

  • Tell the lab if you were having your period, have bleeding hemorrhoids or exercised hard, since these can change the result
  • Ask whether a microscope check of the urine, a repeat test or a urine culture would help
  • Bring a list of your medicines and supplements, including blood thinners and pain relievers
  • If hard exercise is the likely cause, ask whether to repeat the test after a couple of days of rest

What can affect your result

  • Menstrual blood and vaginal bleeding can make the strip read positive
  • Hard exercise and dehydration can make the strip read positive
  • Bacteria multiplying in a sample that sat too long can cause a false positive
  • Large amounts of vitamin C (ascorbic acid) can make the strip read falsely low or negative
  • Very concentrated urine, acidic urine (pH under about 5.1), protein in the urine, and the blood pressure medicine captopril can make the strip read falsely low or negative
  • Labs use different reporting words (trace, small, 1+), and strip brands vary in how much heme it takes to turn the pad positive
  • Menstrual blood, vaginal bleeding or bleeding hemorrhoids can get into the sample and cause a positive result.
  • Hard exercise and dehydration can cause a positive result.
  • Hemoglobin and myoglobin turn the pad positive even when there are no intact red blood cells.
  • Bacteria growing in a sample that sits too long can cause a false-positive result.
  • Large amounts of vitamin C (ascorbic acid) can cause a falsely low or negative result.
  • Captopril, very concentrated urine, urine pH below about 5.1 and protein in the urine can cause a falsely low or negative result.

A random midstream sample is fine. Tell the lab if you're menstruating or have bleeding hemorrhoids, since blood from those can get into the sample. It reflects the sample at the moment of collection. Blood from hard exercise is expected to clear on a repeat test after about 48 to 72 hours, and other causes vary.

When to talk to a clinician

See a clinician promptly if you can see blood, or your urine looks pink, red or cola-colored, especially with pain, fever, trouble urinating or clots. Get urgent care if you can't urinate, have severe back or side pain, or feel faint. A trace or small dipstick result without symptoms is usually less urgent, but it should be confirmed with a microscope check and discussed with a clinician, especially if it shows up more than once. For reference, guidelines define microscopic hematuria as 3 or more red blood cells per high-power field on microscopy.

Questions you could ask

  • Are there supplements or activities I should mention or plan around before a repeat test?
  • Should my urine be looked at under a microscope to count red blood cells?
  • Could my period, exercise or a medicine explain this result?
  • Should we repeat the test, and when?
  • Based on my age and history, is any further evaluation needed?

Questions people ask

Why does my dipstick say blood, but the microscope shows no red blood cells?

The strip reacts to heme, not only to whole red blood cells. Red cells can break open in dilute or alkaline urine or as a sample stands, and free hemoglobin or myoglobin from muscle can also turn the strip positive. Your clinician may repeat the test with a fresh sample.

Can my period or exercise cause blood in the urine test?

Yes. Menstrual blood in the sample and hard exercise are well-known reasons for a positive dipstick. Tell the lab if you were menstruating, and ask your clinician whether to repeat the test at another time. Blood from exercise is expected to be gone on a repeat test after about 48 to 72 hours.

What counts as blood in the urine under the microscope?

The American Urological Association defines microscopic hematuria as 3 or more red blood cells per high-power field when the urine is examined under a microscope. The dipstick alone isn't used to define it.

Does vitamin C change this test?

It can. Large amounts of vitamin C can make the strip read falsely low or negative. If you take vitamin C supplements, mention it to your clinician or the lab.

Should I worry about a trace result?

Trace is the weakest positive reading, and it can be caused by harmless things such as menstrual blood or exercise. It's still worth mentioning to your clinician, who may suggest a microscope check or a repeat test, especially if it keeps showing up.

Show the science and sources

For clinicians and researchers

The dipstick blood pad relies on the pseudoperoxidase activity of heme, which catalyzes color development with an organic peroxide and a chromogen. Intact red cells, free hemoglobin and myoglobin all react, so a positive pad may reflect hematuria, hemoglobinuria or myoglobinuria (AFP, StatPearls). Intact erythrocytes on microscopy of the sediment distinguish hematuria from the others. Red cells can lyse in dilute or alkaline urine or on standing, which produces dipstick-positive, microscopy-negative samples. In the studies summarized by AFP (2005), a dipstick result of 1+ blood or higher had a sensitivity of 91–100% and a specificity of 65–99% for microscopic hematuria. The AUA/SUFU guideline (2020) defines microhematuria as 3 or more RBC/HPF on microscopic evaluation of a single specimen and stratifies risk by age, sex, smoking and other factors. The 2025 AUA/SUFU update requires a confirmatory microscopic urinalysis after a positive dipstick (as described by Lan et al., 2025). Older sources, including AFP, used 3 or more RBC/HPF in two of three samples. Laboratory RBC/HPF reporting ranges are not uniform: in a survey of 141 laboratories, 42% used cutoffs that did not match the guideline's risk groups (Sternberg et al., 2021). Reported false positives include dehydration, exercise, menstrual blood, hemoglobinuria, myoglobinuria and bacterial overgrowth. Reported false negatives include ascorbic acid, captopril, high specific gravity, pH below 5.1 and proteinuria (AFP, StatPearls).

LOINC 5794-3 (primary), 57751-0, 49137-3, 50559-4. Specimen: urine.

Sources

  1. Urinalysis, StatPearls Publishing (NCBI Bookshelf) (2023)
  2. Urinalysis: A Comprehensive Review, American Family Physician (2005)
  3. Blood in Urine Test, MedlinePlus (National Library of Medicine)
  4. Microhematuria: AUA/SUFU Guideline, Journal of Urology (2020)
  5. Confirmatory Microscopic Urinalysis After Positive Dipstick Microhematuria: Adherence Patterns and Quality Improvement, Urology (2025)
  6. Laboratory Reporting Parameters of Microhematuria: Implications for Interpreting the 2020 AUA Guideline, Urology (2021)
  7. Urinalysis, Complete With Microscopic Examination (test 003772), Labcorp

AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.

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