Blood in urine, known medically as hematuria, is relatively common in women and has a wide range of causes, from urinary tract infections to kidney stones to, less commonly, bladder cancer. Sometimes the blood is visible, turning urine pink, red, or brown. Other times it’s only detectable under a microscope, where three or more red blood cells per high-power field on a urine sample is considered clinically significant. The cause is often treatable, but visible blood in your urine always warrants a medical evaluation.
Urinary Tract Infections
UTIs are the most common reason women see blood in their urine. Bacteria enter through the urethra and multiply in the bladder, inflaming the bladder lining and causing small amounts of bleeding. Because the female urethra is shorter than the male urethra, bacteria have a shorter path to travel, which is why UTIs are far more frequent in women. The blood can make urine look pink, red, or brownish, and it typically comes alongside burning during urination, a persistent urge to go, and sometimes pelvic pressure or cloudy, strong-smelling urine.
A simple urine culture confirms the diagnosis, and the bleeding usually stops within a day or two of starting antibiotics. If you get recurrent UTIs with blood, your doctor may want to rule out other causes before attributing it to infection alone.
Kidney and Bladder Stones
Stones form when minerals in your urine crystallize and clump together. A stone sitting quietly in the kidney often causes no symptoms at all. The trouble starts when it moves into one of the narrow tubes connecting your kidneys to your bladder, or when it shifts within the kidney itself. The hard edges of the stone scrape against the soft lining of the urinary tract, causing bleeding that turns urine pink, red, or brown.
The hallmark symptom is intense, wave-like pain in the back or side that radiates toward the lower abdomen and groin. Nausea, vomiting, fever, and chills can accompany the pain. Small stones often pass on their own within days to weeks. Larger stones may need procedures to break them up or remove them.
Menstruation and Vaginal Sources
One of the most overlooked explanations is simple contamination from menstrual blood. During your period, or even with spotting between periods, blood can mix with urine during collection and appear to be hematuria. This is why doctors typically ask you to provide a urine sample at a time when you’re not menstruating, or to use a clean-catch technique. Vaginal infections or cervical irritation can also produce blood that gets mistaken for urinary bleeding. If a urine test comes back positive for blood but no infection or other urinary cause is found, your doctor may investigate vaginal or cervical sources.
Endometriosis Affecting the Urinary Tract
Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, can involve the bladder or the tubes connecting the kidneys to the bladder. When it does, it can cause blood in the urine that follows a cyclical pattern, worsening around the time of your period. You might also notice urinary urgency or frequency. According to Cleveland Clinic specialists, about half of women with endometriosis affecting the ureters have no urinary symptoms until the disease is advanced, while roughly 15% develop visible blood in the urine. Because it often mimics other conditions, urinary tract endometriosis is frequently diagnosed late.
Vigorous Exercise
Intense physical activity, particularly long-distance running, can cause blood in the urine even in healthy women with no underlying kidney or bladder problems. The exact mechanism isn’t fully understood, but repeated impact on the bladder and increased blood flow through the kidneys during exercise both play a role. The key distinguishing feature is that exercise-induced hematuria resolves with rest. If you notice pink or red urine after a hard workout and it clears up within 24 to 72 hours, exercise is the likely explanation. Blood that persists after rest needs further investigation.
Medications and Blood Thinners
Several types of medications can cause or worsen blood in the urine. Blood thinners are the most common culprits, because they reduce your blood’s ability to clot and can make even minor, otherwise-invisible bleeding in the urinary tract become noticeable. Certain antibiotics, pain relievers, diuretics (water pills), seizure medications, and even some oral contraceptives have also been linked to hematuria. If you’re taking a blood thinner and notice red or pink urine, don’t stop the medication on your own, but do let your doctor know. Blood thinners can make hematuria more visible, but they can also unmask an underlying problem that needs its own evaluation.
Bladder and Kidney Cancer
This is the cause most women worry about, and while it’s far less common than infections or stones, it’s the reason doctors take hematuria seriously. Bladder cancer is the most relevant concern, and painless visible blood in the urine is often its earliest and sometimes only symptom. Bladder cancer occurs more often in men than women, but women who develop it tend to be diagnosed at later stages, partly because the blood is initially attributed to UTIs or menstruation.
Known risk factors include smoking (the single biggest risk factor), workplace exposure to certain chemicals found in paints, dyes, and petroleum products, a family history of bladder cancer, and prior radiation therapy to the pelvic area. Kidney cancer can also cause blood in the urine, though it’s less common and typically produces additional symptoms like back pain or unexplained weight loss. Any blood in the urine that can’t be explained by infection, stones, or menstruation, especially in women over 40 or those with risk factors, warrants imaging and possibly a look inside the bladder with a small camera.
Kidney Disease and Inflammation
Conditions that damage the tiny filtering units inside the kidneys can allow red blood cells to leak into the urine. This includes glomerulonephritis (inflammation of the kidney’s filters), which can develop on its own or as part of a broader condition like lupus or an immune disorder. The blood is usually microscopic rather than visible, and it’s often discovered incidentally on a routine urine test. Additional signs that point to a kidney source include protein in the urine, swelling in the legs or around the eyes, and elevated blood pressure.
What the Color and Timing Tell You
Not everything that turns urine red is blood. Beets, blackberries, and rhubarb can produce reddish urine that looks alarming but is completely harmless. Certain medications, including some laxatives and the UTI pain reliever phenazopyridine, turn urine bright orange or red. A urine test quickly distinguishes food or medication effects from actual blood.
When real blood is present, certain patterns help narrow down the source. Blood that appears at the start of urination and then clears suggests it’s coming from the urethra. Blood throughout the entire stream points to the bladder or kidneys. Blood that follows a cyclical, period-linked pattern raises suspicion for endometriosis. Painless blood, especially in women over 40, is treated more urgently because of the association with cancer. Blood accompanied by burning and frequency is most often a UTI, while blood with severe flank pain suggests a stone.
Passing blood clots, having blood in the urine alongside a fever, or experiencing blood that persists for more than a few days without an obvious explanation like menstruation are all signals to seek prompt medical attention rather than waiting to see if it resolves.