Microhematuria Explained: Causes, Symptoms, and Diagnostic Steps
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
TL;DR: Microhematuria means there is blood in the urine in amounts too small to see with the naked eye. It is often found during routine exams and is frequently caused by benign factors such as exercise or a minor infection. It can also point to kidney stones or, more rarely, urinary tract cancer. Diagnosis involves urinalysis, imaging, and sometimes cystoscopy.
Quick answer: Microhematuria occurs when small amounts of blood enter the urine and can be detected only under a microscope. The American Urological Association defines it as three or more red blood cells per high-powered field. Common causes include urinary tract infections (UTIs), vigorous exercise, kidney stones, and certain medications. Most cases are not serious, but about 3% may be linked to cancer. Providers use urinalysis, blood tests, and imaging to find the cause and recommend treatment.
What Is Microhematuria?
Microhematuria, also called microscopic hematuria, is a finding in which red blood cells are present in the urine in amounts too small to see. The urine looks perfectly normal in color, so the condition is usually identified during routine screening or tests for an unrelated problem. The American Urological Association sets the threshold at three or more red blood cells per high-powered field under a microscope.
Finding blood in the urine, even at a microscopic level, can be worrying. It is often a temporary result of non-serious factors. Because it can occasionally be an early sign of something more significant, healthcare providers follow a structured process to find the cause.
Common Causes and Risk Factors
Microhematuria can come from many sources, from temporary physiological changes to chronic conditions. Identifying the source is key to deciding whether treatment is needed.
Infections: Urinary tract infections are the most frequent cause. Read more in our guide to urinary tract infections.
Physiological causes: Vigorous exercise, menstruation, or recent trauma to the urinary tract.
Structural issues: Kidney stones, bladder stones, or an enlarged prostate (BPH). See our kidney stones guide.
Chronic conditions: Chronic kidney disease (CKD) or urethral strictures.
Medications: NSAIDs, penicillin, or anticoagulants (blood thinners).
Serious pathologies: Cancers of the bladder, kidney, or prostate, found in about 3% of cases.
Symptoms and When to Seek Care
Often microhematuria causes no symptoms at all. Depending on the underlying cause, some people notice a more frequent urge to urinate, a painful or burning sensation when urinating (dysuria), or pain in the flank, the area of the lower back just above the hips. Fever and unusually foul-smelling urine are other signs to watch for.
If you have a history of microhematuria and begin to see visible blood in your urine (gross hematuria), contact a healthcare provider right away. Severe symptoms such as high fever or intense flank pain should be evaluated at an urgent care facility.
How Microhematuria Is Diagnosed
Because microhematuria is usually found at a routine checkup, the process starts with a thorough review of your health history. Providers ask about smoking, medication use, and any family history of urinary tract problems or cancer. Several tests may then be ordered to pinpoint the cause:
Urinalysis and urine culture: To confirm red blood cells and identify bacterial infection.
Blood tests: Including a complete blood count (CBC) and kidney function tests to assess overall health and organ performance.
Imaging: A CT urogram or other imaging gives a detailed view of the kidneys, ureters, and bladder.
Cystoscopy: A thin camera is passed into the urethra to examine the inside of the bladder.
Biopsy: In some cases, a small tissue sample is taken from the kidney or bladder for further analysis.
Management and Treatment
Treatment depends entirely on what is causing the blood in the urine. A UTI is usually cleared with a course of antibiotics. For urinary stones, medications to help pass the stone or a procedure to remove it may be needed. If an enlarged prostate is responsible, providers may prescribe medicines to relax the prostate or slow its growth.
When no specific cause is found after thorough testing, providers often recommend "watchful waiting." This means monitoring for new symptoms and repeating urinalysis at scheduled intervals to make sure nothing new develops.
Prevention and Long-Term Outlook
Not every cause can be prevented, but some lifestyle choices lower your risk. Staying well hydrated, especially during exercise, is one of the most effective steps. Quitting smoking and using over-the-counter pain relievers such as NSAIDs only as directed also help protect kidney and bladder health. Our article on the bladder explains more about keeping the urinary tract healthy.
The overall outlook is generally very good. Most underlying causes are benign and easy to treat, and many resolve on their own. Regular screening and follow-up on abnormal results help make sure any problem is caught and managed early.
Conclusion
Microhematuria is a common finding that gives healthcare providers an important diagnostic clue. It often points to a minor issue such as a UTI or the effects of intense exercise, but detecting it allows earlier identification of more serious conditions. Understanding the diagnostic process and the range of causes helps you approach the finding with a balanced perspective and work closely with your medical team.
Talk to a provider: If a routine test has shown microscopic blood in your urine, or you have symptoms such as painful urination or flank pain, consult a healthcare provider or urologist. Early evaluation is the best way to find the cause and get appropriate care.
Frequently Asked Questions
What is microhematuria?
It is the presence of red blood cells in the urine that can be seen only under a microscope.
How is microhematuria defined medically?
The AUA defines it as three or more red blood cells per high-powered field under a microscope.
Can I see microhematuria in my urine?
No. The urine looks normal to the naked eye, and a microscope is needed to detect it.
What is "trace lysed blood" in a urine test?
It refers to a small amount of blood in which the red blood cell walls have broken apart.
What is the most common cause of microhematuria?
Urinary tract infections (UTIs) are the most common cause.
Can exercise cause blood in the urine?
Yes. Vigorous physical activity can sometimes cause temporary microhematuria.
Is microhematuria a common sign of cancer?
It is a sign in about 3% of cases, but most causes are not cancer.
What symptoms might accompany microhematuria?
Symptoms can include frequent urination, pain during urination, flank pain, or fever.
Is microhematuria contagious?
No. The condition itself is not contagious, nor are its most common causes such as UTIs.
What tests are used to diagnose the cause?
Tests include urinalysis, urine culture, blood tests, CT scans, and cystoscopy.
What is a cystoscopy?
It is a procedure in which a small camera is used to look inside the urethra and bladder.
How are UTIs that cause microhematuria treated?
They are typically treated with a course of antibiotics.
What if no cause is found for the blood in my urine?
Providers often recommend watchful waiting and periodic follow-up testing.
Can smoking affect my risk?
Yes. Smoking is a significant risk factor for urinary tract conditions, including those that cause microhematuria.
Can drinking water prevent microhematuria?
Staying well hydrated can help prevent some causes, such as urinary stones and UTIs.
Medical Disclaimer
The information in this article is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have about a medical condition.
Source date: October 21, 2024.
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