Blood in urine, called hematuria, is common in women and has a wide range of causes, from urinary tract infections to kidney stones to menstrual contamination of a urine sample. Sometimes the blood is visible (pink, red, or cola-colored urine), and sometimes it only shows up under a microscope during a routine test. Most causes are treatable and not dangerous, but visible blood in your urine always warrants a medical evaluation because it can occasionally signal something more serious like bladder cancer.
Urinary Tract Infections
UTIs are the most common reason women see blood in their urine. More than half of women will have at least one UTI in their lifetime. Bacteria enter the urinary tract, multiply, and cause inflammation in the bladder lining, which can lead to bleeding. You’ll usually notice other symptoms alongside the blood: burning with urination, a frequent or urgent need to go, cloudy or strong-smelling urine, and sometimes pelvic pressure. UTIs are straightforward to treat with antibiotics, and the blood typically clears as the infection resolves.
Kidney and Bladder Stones
Minerals in your urine can form crystals on the walls of your kidneys or bladder. Over time, these crystals harden into small stones. Many stones cause no symptoms at all while they sit quietly in the kidney. The trouble starts when a stone moves, blocking urine flow or scraping the lining of the urinary tract on its way out. This mechanical irritation is what causes bleeding.
Stones can produce blood visible to the naked eye or blood that only shows up in lab testing. When a stone is actively passing, the pain is usually severe and comes in waves, often radiating from the back or side down toward the groin. If you’re experiencing blood in your urine with that kind of pain, a stone is high on the list of likely causes.
Endometriosis of the Urinary Tract
Endometriosis, a condition where tissue similar to the uterine lining grows outside the uterus, can sometimes affect the bladder or the tubes connecting the kidneys to the bladder. Up to 1% of women with pelvic endometriosis have urinary tract involvement, but in women with deep endometriosis, that number jumps to as high as 50%. The hallmark clue is blood in your urine that follows a cyclical pattern, appearing around the time of your period. You may also notice urinary urgency or frequency that worsens during menstruation.
Intense Exercise
Strenuous physical activity, particularly endurance sports like long-distance running, can cause temporary blood in the urine. Several factors contribute: reduced blood flow to the kidneys during prolonged exertion, rising body temperature, dehydration, and in runners, direct mechanical trauma to the bladder from repeated impact. In endurance athletes, this type of hematuria is usually self-limiting and resolves within 48 to 72 hours. If it persists beyond that window, further evaluation is warranted.
Bladder Cancer
Though less common in women than men, bladder cancer is an important cause to rule out, especially if you’re over 40 and have visible blood in your urine without an obvious explanation like a UTI. Smoking is the single biggest risk factor. Tobacco’s harmful chemicals are absorbed into the bloodstream, filtered by the kidneys, and concentrated in the urine, exposing the bladder lining to carcinogens over years. Other risk factors include workplace exposure to paints, dyes, metals, or petroleum products, a family history of bladder cancer, and past pelvic radiation therapy.
Blood in urine from bladder cancer is often painless, which is what makes it easy to dismiss. Painless, visible hematuria in a woman over 40, particularly one who smokes or has smoked, should always be investigated promptly.
Foods and Medications That Mimic Blood
Not everything that turns urine red is actually blood. Beets, blackberries, and rhubarb can all turn urine pink or red. So can certain medications. A common UTI pain reliever called phenazopyridine turns urine bright reddish-orange. The antibiotic rifampin, used for tuberculosis, does the same. Constipation medicines containing senna can also cause reddish discoloration. If your urine looks off but you recently ate beets or started a new medication, that may be the explanation. A simple urine test can confirm whether actual blood cells are present.
Menstrual Blood and False Positives
Menstrual blood can contaminate a urine sample and make it look like you have hematuria when you don’t. This is one of the most common sources of a false positive result on urine testing. If a urine dipstick comes back positive for blood during or just after your period, your provider will likely ask you to repeat the test at a different point in your cycle. Collecting a sample during a non-menstrual window gives a much more reliable result. Using a clean-catch technique, where you wipe first and catch urine midstream, also helps reduce contamination from vaginal discharge.
How Blood in Urine Is Evaluated
The starting point is a urine dipstick, a quick in-office test that detects the presence of blood. If that’s positive, the next step is urine microscopy, where a lab examines the sample under a microscope. Significant microscopic hematuria is defined as three or more red blood cells per high-power field on a properly collected specimen. Before launching into a full workup, your provider will first rule out common contributing factors: infection, menstruation, vigorous exercise, recent sexual activity, or trauma. If any of these could explain the result, you’ll typically repeat the test after that factor has resolved.
When hematuria is confirmed and unexplained, imaging comes next. An ultrasound of the kidneys and bladder is the recommended first-line imaging test for most patients. In some cases, a contrast-enhanced CT scan is used to get a more detailed picture of the upper urinary tract. For women over 40, or anyone with risk factors for urologic cancer, a cystoscopy is typically recommended. During this procedure, a thin camera is inserted through the urethra to visually inspect the inside of the bladder. It sounds uncomfortable, but it’s usually brief and done in an outpatient setting.
Other Possible Causes
Several additional conditions can produce blood in urine. Kidney infections, which are more serious than simple bladder infections, cause hematuria along with fever, back pain, nausea, and feeling generally unwell. Kidney disease, particularly conditions affecting the tiny filtering units inside the kidney, can allow blood cells to leak into urine over time. Certain blood-thinning medications can make you more prone to urinary bleeding, though the medication itself isn’t usually the root cause; it often unmasks an underlying issue. Trauma to the kidneys or bladder from an injury or accident is another possibility, though in that case the connection is usually obvious.
In some women, no cause is ever identified even after a thorough workup. This is called idiopathic hematuria, and while it can be frustrating, it’s generally managed with periodic monitoring to make sure nothing new develops.