Blood in the urine, called hematuria, is relatively common in women and most often points to a urinary tract infection or another treatable condition rather than something serious. That said, it always warrants investigation because the range of possible causes is wide, from kidney stones and hormonal changes to, less commonly, bladder cancer. Understanding what’s behind it depends on whether the blood is visible to the naked eye, detectable only under a microscope, and what other symptoms accompany it.
Visible vs. Microscopic Blood
There are two types of hematuria, and the distinction matters. Visible (gross) hematuria turns your urine pink, red, or cola-colored, and it’s usually what prompts a search like this one. Microscopic hematuria, on the other hand, can only be detected in a lab. The American Urological Association defines it as more than 3 red blood cells per high-power field on a single, properly collected urine sample.
Visible blood in the urine carries a higher statistical association with serious conditions. In a large 2022 systematic review published in European Urology, about 17% of people with visible hematuria were found to have bladder cancer, compared to roughly 3.3% of those with microscopic hematuria. Those numbers reflect all patients referred for evaluation, not the general population, so the actual risk for any individual woman is lower. Still, visible hematuria generally triggers a more urgent workup than the microscopic kind.
Urinary Tract Infections
UTIs are the single most common reason women see blood in their urine. The short female urethra makes it easier for bacteria to reach the bladder, and when they do, the resulting inflammation can damage the bladder lining enough to release blood. You’ll typically also notice burning during urination, a frequent urge to go, and cloudy or strong-smelling urine. A straightforward UTI clears with antibiotic treatment, and the blood should disappear once the infection resolves. If it doesn’t, that’s a signal to investigate further.
In more severe cases, infection causes what’s known as hemorrhagic cystitis, a deeper inflammation of the bladder wall. This can produce visible clots and significant bleeding. It’s less common but tends to occur in people with weakened immune systems or after certain medical treatments.
Kidney Stones
Kidney stones are another frequent culprit. As a stone moves through the urinary tract, it scrapes the lining of the ureter or bladder, releasing blood. The hallmark symptom is intense, wave-like pain that radiates from the back or side toward the lower abdomen and groin. Some women describe it as worse than labor pain. You may also feel nauseous or notice that your urine looks darker than usual. Small stones often pass on their own within days to weeks, while larger ones may need medical intervention.
Kidney Disease
A condition called glomerulonephritis, where the tiny filtering units inside the kidneys become inflamed, is a common cause of microscopic hematuria. You may not notice any symptoms at all until a routine urine test picks it up. This type of kidney inflammation can develop on its own or as part of a systemic condition like diabetes or lupus. When blood in the urine appears alongside protein in the urine, high blood pressure, or swelling in the legs and feet, it points more strongly toward a kidney-related cause.
Causes Specific to Women
Several causes of hematuria are unique to or more relevant for women. Menstrual blood is a surprisingly common source of a false-positive result. If a urine sample is collected during your period, menstrual blood can contaminate it and mimic hematuria. Doctors will often ask you to repeat the test after menstruation ends before pursuing a full evaluation.
Endometriosis can also involve the urinary tract. When endometrial tissue grows on or into the bladder wall, it can cause blood in the urine that follows a cyclical pattern, worsening around your period. Cleveland Clinic notes that many women with urinary tract endometriosis have no symptoms until the disease is advanced, but those who do may experience cyclic hematuria along with urinary urgency and frequency. If you notice that bloody urine consistently lines up with your menstrual cycle, this is worth mentioning to your doctor.
Sexual activity can also cause minor bleeding, especially if there’s irritation to the urethra. This is typically short-lived and resolves on its own.
Hematuria During Pregnancy
Finding blood in your urine while pregnant is understandably alarming, but the most common cause is still a urinary tract infection, followed by kidney stones. Research published in the American Journal of Kidney Diseases found that the development of preeclampsia, gestational hypertension, or a small-for-gestational-age baby occurred at similar rates in pregnant women with and without microscopic hematuria on a dipstick test. In other words, microscopic hematuria alone isn’t a reliable predictor of pregnancy complications.
That said, hematuria during pregnancy does require attention. If blood in the urine appears alongside high blood pressure, significant protein in the urine, or swelling, the picture changes. These combined findings can signal preeclampsia or an underlying kidney condition, both of which affect how a pregnancy is managed. Blood in the urine from a UTI should clear after treatment. If it persists, further evaluation is warranted even during pregnancy.
Less Common but Serious Causes
Bladder cancer is less common in women than in men, but it does occur, and visible hematuria is often the first sign. The risk rises with age, smoking history, and exposure to certain industrial chemicals. Kidney cancer can also produce blood in the urine, though it accounts for roughly 2% of visible hematuria cases and under 1% of microscopic cases in the systematic review data. Upper urinary tract cancers are rarer still. The overall odds that hematuria signals cancer are relatively low, especially for younger women, but the possibility is exactly why any blood in the urine deserves a proper evaluation.
What Evaluation Typically Looks Like
The first step is usually a urinalysis and urine culture to check for infection. If infection is ruled out or treated and the blood persists, imaging comes next. An ultrasound of the kidneys and bladder is often the starting point, with a CT scan providing more detailed information when needed. In some cases, particularly with visible hematuria or risk factors for cancer, a cystoscopy is performed. This involves a thin camera inserted through the urethra to visually inspect the bladder lining.
Your age, symptoms, and risk factors determine how aggressive the workup is. A 25-year-old with a confirmed UTI and blood that clears after antibiotics may need nothing more. A 55-year-old with painless visible hematuria and a smoking history will likely undergo imaging and cystoscopy promptly.
Other Triggers Worth Knowing
Vigorous exercise can cause temporary hematuria, sometimes called “runner’s hematuria.” It typically resolves within 24 to 72 hours of rest. Certain medications, particularly blood thinners, can make you more prone to urinary bleeding, though the blood thinner itself isn’t the root cause. It’s usually unmasking an underlying issue. Some foods, like beets and blackberries, can turn urine red without any actual blood being present, so a lab test is always the right first step before assuming the worst.
Trauma to the kidneys or bladder, even from a minor fall or car accident, can also produce blood in the urine. A recent urinary tract procedure, such as a catheter placement or biopsy, is another common and expected cause that resolves as the tissue heals.