Urine Red Blood Cells (RBC)
Counts red blood cells in your urine under a microscope or analyzer, per high-power field (HPF). A few can be usual.
AI-verified against cited sources. Awaiting expert reviewAlso called U-RBC, RBC/HPFLOINC 13945-1
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What it is
This test counts the red blood cells in a spun urine sample, using a microscope or an automated analyzer. The count is reported per high-power field (HPF), which is the area you see at high magnification. A few red cells can be usual. A higher count means blood is present in the urine, even if you cannot see it. Doctors call this microscopic hematuria. The count is part of a complete urinalysis and is separate from the dipstick blood pad, which reacts to hemoglobin instead of counting cells.
Why it matters
Blood in the urine has many causes. Many are not serious or are treatable, such as a urinary infection, a kidney stone, hard exercise or a period. Sometimes it is an early clue to a kidney or urinary tract problem. That is why a count of 3 or more per HPF on a properly collected sample is followed up. The microscope count also helps sort out dipstick blood results, because a dipstick alone gives false alarms fairly often.
If it’s high
Three or more red cells per HPF on a properly collected sample is called microscopic hematuria. It is common, and most of the time the cause is not serious. Because it is sometimes linked to the kidneys or urinary tract, clinicians usually check the result with a repeat urinalysis, your history and sometimes other tests.
Common causes
- A urinary tract infection
- Kidney or bladder stones
- Hard exercise or sexual activity before the sample
- Menstrual blood in the sample
- An enlarged prostate
- Some medicines
- Inflammation or other conditions of the kidney filters
- Polycystic kidney disease
- Less often, cancer of the bladder, kidney or prostate
What can help
- If asked to repeat the test, give a midstream clean-catch sample and avoid hard exercise or sexual activity right before. If you have your period, ask when to retest.
- Tell your clinician about blood thinners, other medicines, past kidney stones and past infections
- Ask which follow-up tests, if any, make sense for you
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
The usual range depends on age. Choose an age to see the one that applies.
Children and teens 1 ranges
- under 180–5 /HPF
See Urine RBC by age and sex, with the U.S. survey numbers where they exist.
AUA/SUFU 2025 definition of microhematuria (adults)
- Below the microhematuria thresholdbelow 3 /HPF
- Microhematuria (3 or more per HPF)3 and above /HPF
What can affect your result
- Menstruation
- Vigorous exercise or sexual activity before the sample
- How well the midstream sample was collected, since contamination can add cells
- Dilute urine, which can break red cells apart
- Some medicines
- Counting method: manual microscopy or an automated analyzer
- Time between collection and testing
- Age: children use a higher cut-off (more than 5 per HPF)
- Menstrual blood can add red cells to the sample. The AUA advises retesting after the period ends, or collecting by catheter.
- Vigorous exercise or sexual activity before the sample can cause temporary red cells in the urine.
- Very dilute urine (osmolality below about 308 mOsm, or specific gravity below 1.010) can break red cells apart and lower the count.
- If many squamous epithelial cells are in the sample, red cells may come from contamination, and a repeat sample may be needed.
- Urine that sits for hours before testing can give unreliable results. Samples should be tested promptly or refrigerated.
- Counts depend on the method. Manual microscopy is the reference standard, and automated analyzers can undercount red cells in kidney-filter (glomerular) disease.
A random midstream clean-catch sample is usually enough. The American Urological Association advises not using the first morning void, or a sample right after vigorous exercise or sexual activity, to assess microhematuria. The count reflects the sample you gave. Red cells from exercise or another short-lived cause are usually gone on a repeat urinalysis a few days later, while blood in the urine that persists is judged over repeated samples.
When to talk to a clinician
Contact a clinician soon if you can see blood in your urine (pink, red or brown), or if red cells show up on more than one test. A count of 3 or more per HPF in adults is the usual line for follow-up. Get prompt care if blood comes with fever, pain in your side, back or belly, or pain when you urinate.
Questions you could ask
- Does my dipstick blood result match my microscope red cell count?
- Should we repeat the urinalysis on a clean-catch sample, and when?
- Could my period, exercise, an infection or a medicine explain this?
- What follow-up tests, if any, would you suggest for me, and why?
- Is my kidney function and urine protein worth checking too?
Questions people ask
What does RBC/HPF mean, and why does my report show ranges like 0-2?
HPF stands for high-power field, the area seen under the microscope at high magnification. RBC/HPF is the number of red blood cells counted in that area. Some labs report grouped counts, such as 0-2, 3-5 and 6-10 per HPF, instead of one number. Because labs prepare and count samples a little differently, the same urine can give different counts at different labs.
My dipstick said blood but the microscope count was low. Is that a problem?
Not necessarily. The dipstick reacts to hemoglobin and similar substances, so it can read positive when few red cells are present. Dehydration, hard exercise, menstrual blood, myoglobin and povidone-iodine can all do this. In one study of 237 women with a positive dipstick, about 1 in 5 had a normal urinalysis. Guidelines say a dipstick alone should not define microhematuria, so your clinician may repeat the urinalysis.
Can my period or exercise cause red cells in my urine?
Yes. Menstrual blood can get into the sample, and hard exercise or sexual activity can cause temporary red cells. Tell the person collecting your sample if you have your period, and ask when to retest.
I take blood thinners. Does that explain blood in my urine?
Not on its own. Guidelines say clinicians should look into microhematuria the same way whether or not you take blood thinners or antiplatelet medicines. Tell your clinician about everything you take.
Can I convert red cells per microliter to per HPF?
Not exactly. Some labs, especially outside the US, report red cells per microliter from an automated analyzer. The size of a high-power field and how the sample is prepared vary, so the two units cannot be converted reliably. Compare results only in the same unit, and use the range printed on your report.
Show the science and sources
For clinicians and researchers
AUA/SUFU (2025) defines microhematuria as 3 or more RBC per HPF on microscopic evaluation of a single, properly collected urine specimen, and says it should not be defined by a positive dipstick alone. A dipstick reading of trace blood or more should prompt microscopy. The panel urges laboratories to report RBC/HPF quantitatively, notes that microscopic quantification remains the referent standard, and finds insufficient evidence on the accuracy of automated devices. In children, microhematuria is generally defined as more than 5 RBC/HPF (AFP 2022). Preparation matters: about 10 mL of urine is centrifuged for 5 minutes and the pellet resuspended before counting (AFP 2022), so HPF counts depend on technique and cannot be converted exactly to cells per microliter. Dilute urine (osmolality below about 308 mOsm) lyses RBCs and lowers counts, and in a Korean cohort about 20% of specimens had a specific gravity below 1.010, which made automated counts unreliable. In the same study, automated analyzers underestimated hematuria in glomerular disease (Yang 2021). The AUA advises against using a first-morning void or a sample taken right after vigorous exercise or sexual activity, and many squamous cells suggest contamination. Dysmorphic RBCs and RBC casts point to a glomerular source. KDIGO 2024 lists urinary red cell casts, or an unexplained sustained count above 20 RBC/HPF, as reasons for referral to kidney specialist care, and counts persistent hematuria as a marker of kidney damage when present for at least 3 months. Dipstick blood is more than 90% sensitive but gives false positives from myoglobin, free hemoglobin, dehydration, exercise, menstrual blood and povidone-iodine. In one series, 20.3% of 237 women with a positive dipstick had a normal urinalysis (AUA).
LOINC 13945-1 (primary), 5808-1, 105107-7, 46419-8. Specimen: urine.
Sources
- Updates to Microhematuria: AUA/SUFU Guideline (2025), American Urological Association / Society of Urodynamics, Female Pelvic Medicine & Urogenital Reconstruction (2025)
- Office-Based Urinalysis: A Comprehensive Review, American Family Physician 2022;106(1):27-35B (2022)
- Urinalysis: A Comprehensive Review, American Family Physician 2005;71(6):1153-1162 (2005)
- RBC urine test, MedlinePlus Medical Encyclopedia (U.S. National Library of Medicine) (2025)
- Blood in Urine, MedlinePlus (U.S. National Library of Medicine)
- Urinalysis: What It Is, Purpose & Results, Cleveland Clinic (2024)
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease, Kidney International 105(4S):S117-S314 (2024)
- Automated urine sediment analyzers underestimate the severity of hematuria in glomerular diseases, Scientific Reports 2021;11:20981 (2021)
- Urinalysis, Complete (test 003772) sample patient report with reference intervals, Labcorp (2026)
- Urinalysis, Complete With Microscopic Examination (test 003772), Labcorp
- LOINC codes verified with the NLM Clinical Tables LOINC search (e.g. 13945-1), U.S. National Library of Medicine
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.