Microscopic hematuria means there are red blood cells in your urine, but too few to see with the naked eye. It’s typically discovered during a routine urinalysis, and the threshold for diagnosis is 3 or more red blood cells per high-power field when the sample is examined under a microscope. Most of the time, the cause is benign, but in about 2% of cases involving asymptomatic microscopic hematuria, it turns out to be a urinary tract cancer.
How It’s Detected
Most people learn they have microscopic hematuria after a urine dipstick test comes back positive for blood. The dipstick is a quick screening tool, but it’s not always accurate. False positives can happen with concentrated urine, very alkaline urine, strenuous exercise, menstrual contamination, or certain bacterial infections. Myoglobin, a protein released from damaged muscle, also triggers a positive reading even though no red blood cells are present.
Because of these limitations, a positive dipstick alone doesn’t confirm microscopic hematuria. The diagnosis requires a microscopic examination of a urine sample, where a lab technician actually counts the red blood cells. If the count is 3 or more per high-power field, it’s considered true microscopic hematuria and may warrant further evaluation depending on your risk profile.
Common Causes
The list of things that can put a small amount of blood in your urine is long, and most of them aren’t dangerous:
- Urinary tract infections or inflammation of the bladder, kidney, or urethra
- Kidney stones or other urinary tract stones
- Vigorous exercise, particularly long-distance running
- An enlarged prostate in men (benign prostatic hyperplasia)
- Recent sexual activity
- Trauma to the kidneys or bladder
- Endometriosis affecting the urinary tract
- Recent urinary tract procedures, such as catheterization
A recent bacterial or viral infection, including strep throat or hepatitis, can also cause temporary blood in the urine. In younger adults without other risk factors, infections, kidney stones, and exercise are by far the most frequent explanations. Cancer becomes a more significant concern as people age, particularly after 60.
Why Risk Stratification Matters
Not everyone with microscopic hematuria needs the same workup. The American Urological Association’s 2025 guidelines sort patients into low, intermediate, and high risk categories for urinary tract cancer. The factors that determine your category include your age, sex, how many red blood cells were found, your smoking history, and whether you have other risk factors.
If you fall into the low-risk group, you may simply need a repeat urine test to see if the blood persists. If it’s gone on the retest, you’re generally in the clear. If it persists, you move up to at least the intermediate-risk category regardless of your other factors.
Intermediate-risk patients typically undergo a kidney ultrasound and cystoscopy (a procedure where a thin camera is passed into the bladder to look for abnormalities). This group includes women 60 and older, men between 40 and 59, anyone with 11 to 25 red blood cells per high-power field, and people with 10 to 30 pack-years of smoking history.
High-risk patients get a more thorough evaluation: a CT scan of the abdomen and pelvis with contrast (called a CT urogram) plus cystoscopy. You’re considered high-risk if you’re a man 60 or older, have more than 25 red blood cells per high-power field, have a history of visible blood in your urine, or have more than 30 pack-years of smoking. Notably, women are not placed in the high-risk category based on age alone. They need at least one additional risk factor to qualify.
The Cancer Question
This is usually the concern driving the search. A population-based study that eliminated referral bias found that among 2,305 patients with asymptomatic microscopic hematuria, 1.6% had bladder cancer, 0.3% had cancer of the upper urinary tract, and 0.2% had kidney cancer. That adds up to roughly a 2% overall cancer rate. For comparison, patients with visible blood in the urine had an 11% cancer prevalence, making microscopic hematuria a much lower-risk finding.
Several factors push your individual risk higher: a significant smoking history, occupational exposure to chemicals like benzene or aromatic amines, a family history of Lynch syndrome or hereditary kidney tumor syndromes, prior pelvic radiation, and persistent or worsening hematuria over time. Persistent, unexplained urinary urgency or frequency also raises concern. The more of these factors you have, the more important a thorough evaluation becomes.
What to Expect During Evaluation
The first step is usually a repeat urine test to confirm the finding. If you had a urinary tract infection, vigorous exercise, or menstruation at the time of the initial test, those factors should be addressed first and the urine rechecked afterward.
If microscopic hematuria is confirmed, the next steps depend on your risk category. For low-risk patients, monitoring with repeat urinalysis may be all that’s needed. For intermediate and high-risk patients, imaging and cystoscopy are the standard next steps. A cystoscopy takes about 5 to 10 minutes, is done with local numbing gel, and involves mild discomfort rather than significant pain. Imaging (ultrasound or CT urogram) is painless, though the CT version requires an IV contrast injection.
If all of these tests come back normal, the hematuria is considered unexplained but low-concern. Your provider will typically recommend periodic follow-up urinalyses to make sure the finding doesn’t progress. If the hematuria resolves on its own, no further workup is usually needed.
Age and Sex Differences
Age is one of the strongest predictors of whether microscopic hematuria signals something serious. In adults under 40 without smoking history or other risk factors, cancer is rare. The most common culprits in younger people are infections, kidney stones, and exercise-related hematuria, all of which tend to resolve on their own or with straightforward treatment.
The guidelines reflect the fact that women develop urinary tract cancers at lower rates than men. The 2025 update shifted the age threshold for women in the low-risk group from under 50 to under 60, and women can no longer be classified as high-risk based on age alone. Men 60 and older, on the other hand, are automatically high-risk even without additional factors. This doesn’t mean microscopic hematuria in women should be ignored, but it does mean the evaluation can often be less aggressive when no other risk factors are present.